MedWorm.com provides a medical RSS filtering service. Over 6000 RSS medical sources are combined and output via different filters. This feed contains the latest items from the 'Theoretical Population Biology' source. Mon, 15 Mar 2010 16:31:49 +0100 http://www.medworm.com/index.php?rid=3354625&cid=s_36104_62_f&fid=36104&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D20214914%26dopt%3DAbstract We present a simple model in which competition between the exploitation of resources and stochastic fluctuations leads to victory by either the faster or slower of two species depending on the environmental parameters. A simplified limiting case of the model, analyzed by closing the moment and correlation hierarchy, quantitatively predicts which species will win in the complete model under given parameters of spatial variation and average carrying capacity. PMID: 20214914 [PubMed - as supplied by publisher] (Source: Theoretical Population Biology) Theoretical Population Biology journals http://www.medworm.com/rss/comments.php?id=3354625 Sat, 06 Mar 2010 00:00:00 +0100 3354625 http://www.medworm.com/index.php?rid=3354624&cid=s_36104_62_f&fid=36104&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D20214915%26dopt%3DAbstract Authors: Altenberg L Feldman and Karlin conjectured that the number of isolated fixed points for deterministic models of viability selection and recombination among n possible haplotypes has an upper bound of 2(n)-1. Here a proof is provided. The upper bound of 3(n-1) obtained by Lyubich et al. (2001) using Bézout's Theorem (1779) is reduced here to 2(n) through a change of representation that reduces the third-order polynomials to second order. A further reduction to 2(n)-1 is obtained using the homogeneous representation of the system, which yields always one solution 'at infinity'. While the original conjecture was made for systems of selection and recombination, the results here generalize to viability selection with any arbitrary system of bi-parental transmission, which incl... Theoretical Population Biology journals http://www.medworm.com/rss/comments.php?id=3354624 Sat, 06 Mar 2010 00:00:00 +0100 3354624 http://www.medworm.com/index.php?rid=3327997&cid=s_36104_62_f&fid=36104&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D20188120%26dopt%3DAbstract Authors: Brøns M, Kaasen R We consider a three-variable forest pest model, proposed by Rinaldi & Muratori (1992) [Rinaldi, S., Muratori, S., 1992. Limit Cycles in Slow-Fast Forest-Pest Models. Theor. Popul. Biol. 41, 26-43]. The model allows relaxation oscillations where long pest-free periods are interspersed with outbreaks of high pest concentration. For small values of the time scale of the young trees, the model can be reduced to a two-dimensional model. By a geometrical analysis we identify a canard explosion in the reduced model, that is, a change over a narrow parameter interval from outbreak dynamics to small oscillations around an endemic state. For larger values of the time scale of the young trees the two-dimensional approximation breaks down, and a broader paramete... Theoretical Population Biology journals http://www.medworm.com/rss/comments.php?id=3327997 Tue, 23 Feb 2010 00:00:00 +0100 3327997 http://www.medworm.com/index.php?rid=3302818&cid=s_36104_62_f&fid=36104&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D20171975%26dopt%3DAbstract Authors: Roques L, Hamel F, Fayard J, Fady B, Klein EK Diffusion is one of the most frequently used assumptions to explain dispersal. Diffusion models and in particular reaction-diffusion equations usually lead to solutions moving at constant speeds, too slow compared to observations. As early as 1899, Reid had found that the rate of spread of tree species migrating to northern environments at the beginning of the Holocene was too fast to be explained by diffusive dispersal. Rapid spreading is generally explained using long distance dispersal events, modelled through integro-differential equations (IDEs) with exponentially unbounded (EU) kernels, i.e. decaying slower than any exponential. We show here that classical reaction-diffusion models of the Fisher-Kolmogorov-Petrovsky-Piskunov ... Theoretical Population Biology journals http://www.medworm.com/rss/comments.php?id=3302818 Thu, 18 Feb 2010 00:00:00 +0100 3302818 http://www.medworm.com/index.php?rid=3267958&cid=s_36104_62_f&fid=36104&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D20149814%26dopt%3DAbstract Authors: Rouzine IM, Coffin JM The adverse effect of co-inheritance linkage of a large number of sites on adaptation has been studied extensively for asexual populations. However, it is insufficiently understood for multi-site populations in the presence of recombination. In the present work motivated by our studies of HIV evolution in infected patients, we consider a model of haploid populations with infrequent recombination. We assume that small quantities of beneficial alleles preexist at a large number of sites and neglect new mutation. Using a generalized form of the traveling wave method, we show that the effectiveness of recombination is impeded and the adaptation rate is decreased by inter-sequence correlations, arising due to the fact that some pairs of homologous sites have c... Theoretical Population Biology journals http://www.medworm.com/rss/comments.php?id=3267958 Mon, 08 Feb 2010 00:00:00 +0100 3267958 http://www.medworm.com/index.php?rid=3236617&cid=s_36104_62_f&fid=36104&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D20117125%26dopt%3DAbstract Authors: Ghirlanda S, Enquist M, Perc M We consider models of the interactions between human population dynamics and cultural evolution, asking whether they predict sustainable or unsustainable patterns of growth. Phenomenological models predict either unsustainable population growth or stabilization in the near future. The latter prediction, however, is based on extrapolation of current demographic trends and does not take into account causal processes of demographic and cultural dynamics. Most existing causal models assume (or derive from simplified models of the economy) a positive feedback between cultural evolution and demographic growth, and predict unlimited growth in both culture and population. We augment these models taking into account that: (1) cultural transmission is not ... Theoretical Population Biology journals http://www.medworm.com/rss/comments.php?id=3236617 Thu, 28 Jan 2010 00:00:00 +0100 3236617 http://www.medworm.com/index.php?rid=3223879&cid=s_36104_62_f&fid=36104&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D20109479%26dopt%3DAbstract Authors: Ghosh A, Haccou P Introgression is the permanent incorporation of genes from one population into another through hybridization and backcrossing. It can have large environmental consequences, such as the spread of insecticide or herbicide resistance genes, the escape of transgenes from genetically modified crops, and the invasion of exotic genes into new habitats. Introgression usually involves strong random components, such as rare hybridization and backcrossing events, and demographic variation in reproduction and survival. Most introgression studies ignore these random effects, and consequently fail to accurately assess the risk of introgression. This paper presents a methodology for quantifying stochastic introgression processes, based on multitype branching process models.... Theoretical Population Biology journals http://www.medworm.com/rss/comments.php?id=3223879 Mon, 25 Jan 2010 00:00:00 +0100 3223879 http://www.medworm.com/index.php?rid=3212726&cid=s_36104_62_f&fid=36104&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D20096297%26dopt%3DAbstract Authors: Wrzaczek S, Kuhn M, Prskawetz A, Feichtinger G We show that in a large class of distributed optimal control models (DOCM), where population is described by a McKendrick type equation with an endogenous number of newborns, the reproductive value of Fisher shows up as part of the shadow price of the population. Depending on the objective function, the reproductive value may be negative. Moreover, we show results of the reproductive value for changing vital rates. To motivate and demonstrate the general framework, we provide examples in health economics, epidemiology, and population biology. PMID: 20096297 [PubMed - as supplied by publisher] (Source: Theoretical Population Biology) Theoretical Population Biology journals http://www.medworm.com/rss/comments.php?id=3212726 Fri, 22 Jan 2010 00:00:00 +0100 3212726 http://www.medworm.com/index.php?rid=3194523&cid=s_36104_62_f&fid=36104&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D20085779%26dopt%3DAbstract Authors: Chevalet C, Nikolic N We investigate the effects of past changes of the effective population size on the present allelic diversity at a microsatellite marker locus. We first derive the analytical expression of the generating function of the joint probabilities of the time to the Most Recent Common Ancestor for a pair of alleles and of their distance (the difference in allele size). We give analytical solutions in the case of constant population size and geometrical mutation model. Otherwise numerical inversion allows the distributions to be calculated in general cases. The effects of population expansion or decrease and the possibility to detect an ancient bottleneck are discussed. The method is extended to samples of three and four alleles, which allows investigating the cova... Theoretical Population Biology journals http://www.medworm.com/rss/comments.php?id=3194523 Sat, 16 Jan 2010 00:00:00 +0100 3194523 http://www.medworm.com/index.php?rid=3172249&cid=s_36104_62_f&fid=36104&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D20064540%26dopt%3DAbstract Authors: Rosenberg NA, Degnan JH Given a gene tree and a species tree, a coalescent history is a list of the branches of the species tree on which coalescences in the gene tree take place. Each pair consisting of a gene tree topology and a species tree topology has some number of possible coalescent histories. Here we show that for each n>/=7, there exist a species tree topology S and a gene tree topology G not equalS, both with n leaves, for which the number of coalescent histories exceeds the corresponding number of coalescent histories when the species tree topology is S and the gene tree topology is also S. This result has the interpretation that the gene tree topology G discordant with the species tree topology S can be produced by the evolutionary process in more ways than can... Theoretical Population Biology journals http://www.medworm.com/rss/comments.php?id=3172249 Fri, 08 Jan 2010 00:00:00 +0100 3172249 http://www.medworm.com/index.php?rid=3129940&cid=s_36104_62_f&fid=36104&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D20036681%26dopt%3DAbstract Authors: Le Rouzic A, Skaug HJ, Hansen TF Artificial-selection experiments on plants and animals generate large datasets reporting phenotypic changes in the course of time. The dynamics of the changes reflect the underlying genetic architecture, but only simple statistical tools have so far been made available to analyze such time series. This manuscript describes a general statistical framework based on random-effect models aiming at estimating key parameters of genetic architectures from artificial-selection responses. We derive explicit Mendelian models (in which the genetic architecture relies on one or two large-effect loci), and compare them with classical polygenic models. With simulations, we show that the models are accurate and powerful enough to provide useful estimates from... Theoretical Population Biology journals http://www.medworm.com/rss/comments.php?id=3129940 Thu, 24 Dec 2009 00:00:00 +0100 3129940 http://www.medworm.com/index.php?rid=3105417&cid=s_36104_62_f&fid=36104&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D20005884%26dopt%3DAbstract In this study we incorporate positive resource-mediated interactions in classic resource competition theory and investigate the main consequences for plant population dynamics and species coexistence. We focus on plant communities for which water infiltration rates exhibit positive dependency on plant biomass and where plant responses can be improved by shading, particularly under water limiting conditions. We show that the effects of these two resource-mediated positive interactions are similar and additive. We predict that positive interactions shift the transition points between different species compositions along environmental gradients and that realized niche widths will expand or shrink. Furthermore, continuous transitions between different community compositions can become disconti... Theoretical Population Biology journals http://www.medworm.com/rss/comments.php?id=3105417 Thu, 10 Dec 2009 00:00:00 +0100 3105417 http://www.medworm.com/index.php?rid=3105418&cid=s_36104_62_f&fid=36104&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D20005241%26dopt%3DAbstract Authors: Hu XS Selection on nuclear (or organelle) sites inevitably affects the spatial distribution of a neutral organelle (or nuclear) allele via transient cytonuclear disequilibrium. Here I examine this effect in terms of F(st) for a neutral allele by bringing together cytonuclear genomes with contrasting modes of inheritance. The relationships between cytonuclear disequilibrium and increment in F(st) are explored and confirmed through Monte Carlo simulations. Results show that the transient increment in F(st) for a neutral allele is not only related to the vectors of seed and pollen dispersal but also to the mode of its inheritance. Such increments can be substantial in certain conditions. Seed dispersal is more effective than pollen dispersal in changing the transient increment. T... Theoretical Population Biology journals http://www.medworm.com/rss/comments.php?id=3105418 Wed, 09 Dec 2009 00:00:00 +0100 3105418 http://www.medworm.com/index.php?rid=3048961&cid=s_36104_62_f&fid=36104&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D19948179%26dopt%3DAbstract In this study, simulation is used to estimate the impact of social network structure on the probability of an SIR epidemic occurring and, if it does, the final size. Increases in assortativity and clustering coefficient are associated with smaller epidemics and the impact is cumulative. Derived values of R(0) over networks with the highest property values are more than 20% lower than those derived from simulations with zero values of these network properties. PMID: 19948179 [PubMed - as supplied by publisher] (Source: Theoretical Population Biology) Theoretical Population Biology journals http://www.medworm.com/rss/comments.php?id=3048961 Fri, 27 Nov 2009 00:00:00 +0100 3048961 http://www.medworm.com/index.php?rid=3048962&cid=s_36104_62_f&fid=36104&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D19945475%26dopt%3DAbstract Authors: Kuang JJ, Chesson P We study frequency-dependent seed predation (FDP) in a model of competing annual plant species in a variable environment. The combination of a variable environment and competition leads to the storage-effect coexistence mechanism (SE), which is a leading hypothesis for coexistence of desert annual plants. However, seed predation in such systems demands attention to coexistence mechanisms associated with predation. FDP is one such mechanism, which promotes coexistence by shifting predation to more abundant plant species, facilitating the recovery of species perturbed to low density. When present together, FDP and SE interact, undermining each other's effects. Predation weakens competition, and therefore weakens mechanisms associated with competition: here SE... Theoretical Population Biology journals http://www.medworm.com/rss/comments.php?id=3048962 Thu, 26 Nov 2009 00:00:00 +0100 3048962 http://www.medworm.com/index.php?rid=3008979&cid=s_36104_62_f&fid=36104&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D19917301%26dopt%3DAbstract In conclusion, the formation of a search image causes the predator to control the prey densities such that the ratio of available prey is kept constant by the predator. PMID: 19917301 [PubMed - as supplied by publisher] (Source: Theoretical Population Biology) Theoretical Population Biology journals http://www.medworm.com/rss/comments.php?id=3008979 Fri, 13 Nov 2009 00:00:00 +0100 3008979 http://www.medworm.com/index.php?rid=2977840&cid=s_36104_62_f&fid=36104&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D19896491%26dopt%3DAbstract Authors: Durrett R, Moseley S Inspired by previous work of Iwasa, Nowak, and Michor (2006), and Haeno, Iwasa, and Michor (2007), we consider an exponentially growing population of cancerous cells that will evolve resistance to treatment after one mutation or display a disease phenotype after two or more mutations. We prove results about the distribution of the first time when k mutations have accumulated in some cell, and about the growth of the number of type k cells. We show that our results can be used to derive the previous results about the tumor grown to a fixed size. PMID: 19896491 [PubMed - as supplied by publisher] (Source: Theoretical Population Biology) Theoretical Population Biology journals http://www.medworm.com/rss/comments.php?id=2977840 Wed, 04 Nov 2009 00:00:00 +0100 2977840 http://www.medworm.com/index.php?rid=2977841&cid=s_36104_62_f&fid=36104&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D19895825%26dopt%3DAbstract We present a single, comprehensible analytical result which summarizes most effects of environmental fluctuations on evolutionary branching driven by resource competition. Corroborating earlier findings, we show that branching may be delayed or impeded if the underlying resources have uncorrelated or negatively correlated responses to environmental fluctuations. There is also a strong impeding effect of positive environmental autocorrelation, which can be related to results from recent experiments on adaptive radiation in bacterial microcosms. In addition, we find that environmental fluctuations can lead to cycles of repeated branching and extinction. PMID: 19895825 [PubMed - as supplied by publisher] (Source: Theoretical Population Biology) Theoretical Population Biology journals http://www.medworm.com/rss/comments.php?id=2977841 Tue, 03 Nov 2009 00:00:00 +0100 2977841 http://www.medworm.com/index.php?rid=2923963&cid=s_36104_62_f&fid=36104&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D19850057%26dopt%3DAbstract Authors: Shimatani IK Spatially explicit models relating to plant populations have developed little since Felsenstein (1975) pointed out that if limited seed dispersal causes clustering of individuals, such models cannot reach an equilibrium. This paper aims to resolve this issue by modifying the Neyman-Scott cluster point process. The new point processes are dynamic models with random immigration, and the continuous increase in the clustering of individuals stops at some level. Hence, an equilibrium state is achieved, and new individual-based spatially explicit neutral coalescent models are established. By fitting the spatial structure at equilibrium to individual spatial distribution data, we can indirectly estimate seed dispersal and effective population density. These estimates are... Theoretical Population Biology journals http://www.medworm.com/rss/comments.php?id=2923963 Mon, 19 Oct 2009 00:00:00 +0100 2923963 http://www.medworm.com/index.php?rid=2917027&cid=s_36104_62_f&fid=36104&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D19843476%26dopt%3DAbstract Authors: Jain K We study the evolutionary dynamics of a haploid population of infinite size recombining with a probability r in a two locus model. Starting from a low fitness locus, the population is evolved under mutation, selection and recombination until a finite fraction of the population reaches the fittest locus. An analytical method is developed to calculate the fixation time T to the fittest locus for various choices of epistasis. We find that (1) for negative epistasis, T decreases slowly for small r but decays fast at larger r (2) for positive epistasis, T increases linearly for small r and mildly for large r (3) for compensatory mutation, T diverges as a power law with logarithmic corrections as the recombination fraction approaches a critical value. Our calculations are see... Theoretical Population Biology journals http://www.medworm.com/rss/comments.php?id=2917027 Fri, 16 Oct 2009 23:00:00 +0100 2917027 http://www.medworm.com/index.php?rid=2917026&cid=s_36104_62_f&fid=36104&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D19843477%26dopt%3DAbstract Authors: Boettiger C, Dushoff J, Weitz JS We derive an expression for the variation between parallel trajectories in phenotypic evolution, extending the well known result that predicts the mean evolutionary path in adaptive dynamics or quantitative genetics. We show how this expression gives rise to the notion of fluctuation domains-parts of the fitness landscape where the rate of evolution is very predictable (due to fluctuation dissipation) and parts where it is highly variable (due to fluctuation enhancement). These fluctuation domains are determined by the curvature of the fitness landscape. Regions of the fitness landscape with positive curvature, such as adaptive valleys or branching points, experience enhancement. Regions with negative curvature, such as adaptive peaks, experien... Theoretical Population Biology journals http://www.medworm.com/rss/comments.php?id=2917026 Fri, 16 Oct 2009 23:00:00 +0100 2917026 http://www.medworm.com/index.php?rid=2909690&cid=s_36104_62_f&fid=36104&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D19836408%26dopt%3DAbstract In this study, we use the Price equation to derive many such well-known results for the dynamics and equilibria of variances in a straightforward way and to develop them further. PMID: 19836408 [PubMed - as supplied by publisher] (Source: Theoretical Population Biology) Theoretical Population Biology journals http://www.medworm.com/rss/comments.php?id=2909690 Tue, 13 Oct 2009 23:00:00 +0100 2909690 http://www.medworm.com/index.php?rid=2887250&cid=s_36104_62_f&fid=36104&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D19819249%26dopt%3DAbstract Authors: Trotter MV, Spencer HG We examine the characteristics of non-equilibrium dynamics produced by a simple well-known model of frequency-dependent selection at a single diploid locus. An examination of the parameter space of this "pairwise-interaction model" (PIM) revealed non-equilibrium dynamics for polymorphisms of 3, 4 and 5 alleles; both allele-frequency cycling and aperiodic trajectories were detected. We measured the number, cycle length and domains of attraction of the various attractors produced by the model. Domains of attraction tended to be smaller, and cycles longer, for systems with larger number of alleles. Fitnesses that parametrized negative frequency-dependent selection were more likely to allow cycling, and these cycles also had larger domains of attraction. Ape... Theoretical Population Biology journals http://www.medworm.com/rss/comments.php?id=2887250 Wed, 07 Oct 2009 23:00:00 +0100 2887250 http://www.medworm.com/index.php?rid=2887252&cid=s_36104_62_f&fid=36104&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D19818799%26dopt%3DAbstract Authors: Ricotta C, Szeidl L Many applications of diversity indices are only valid if they are first transformed into their equivalent number of species. These equivalent numbers of species can be multiplicatively partitioned into independent alpha, beta and gamma components, and can be formed into mathematically consistent similarity measures. The utility of beta diversity and similarity measures that incorporate information about the degree of ecological dissimilarity between species is becoming increasingly recognized. The concept of equivalent number of species is here extended to Rao's quadratic entropy, opening the way to methods of diversity partitioning that take into account taxonomic or ecological differences between species. PMID: 19818799 [PubMed - as supplied by publis... Theoretical Population Biology journals http://www.medworm.com/rss/comments.php?id=2887252 Tue, 06 Oct 2009 23:00:00 +0100 2887252 http://www.medworm.com/index.php?rid=2887251&cid=s_36104_62_f&fid=36104&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D19818800%26dopt%3DAbstract Authors: Gertz J, Gerke JP, Cohen BA With technological advances in genetic mapping studies more of the genes and polymorphisms that underlie Quantitative Trait Loci (QTL) are now being identified. As the identities of these genes become known there is a growing need for an analysis framework that incorporates the molecular interactions affected by natural polymorphisms. As a step towards such a framework we present a molecular model of genetic variation in sporulation efficiency between natural isolates of the yeast, Saccharomyces cerevisiae. The model is based on the structure of the regulatory pathway that controls sporulation. The model captures the phenotypic variation between strains carrying different combinations of alleles at known QTL. Compared to a standard linear model the ... Theoretical Population Biology journals http://www.medworm.com/rss/comments.php?id=2887251 Tue, 06 Oct 2009 23:00:00 +0100 2887251 http://www.medworm.com/index.php?rid=2847077&cid=s_36104_62_f&fid=36104&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D19781561%26dopt%3DAbstract Authors: Cowell RG A simple and efficient algorithm is presented for finding a maximum likelihood pedigree using microsatellite (STR) genotype information on a complete sample of related individuals. The computational complexity of the algorithm is at worst (O(n(3)2(n))), where n is the number of individuals. Thus it is possible to exhaustively search the space of all pedigrees of up to thirty individuals for one that maximizes the likelihood. A priori age and sex information can be used if available, but is not essential. The algorithm is applied in a simulation study, and to some real data on humans. PMID: 19781561 [PubMed - as supplied by publisher] (Source: Theoretical Population Biology) Theoretical Population Biology journals http://www.medworm.com/rss/comments.php?id=2847077 Mon, 21 Sep 2009 23:00:00 +0100 2847077 http://www.medworm.com/index.php?rid=2821493&cid=s_36104_62_f&fid=36104&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D19765601%26dopt%3DAbstract Authors: Chalub FA, Souza MO We study the large population limit of the Moran process, under the assumption of weak-selection, and for different scalings. Depending on the particular choice of scalings, we obtain a continuous model that may highlight the genetic-drift (neutral evolution) or natural selection; for one precise scaling, both effects are present. For the scalings that take the genetic-drift into account, the continuous model is given by a singular diffusion equation, together with two conservation laws that are already present at the discrete level. For scalings that take into account only natural selection, we obtain a hyperbolic singular equation that embeds the Replicator Dynamics and satisfies only one conservation law. The derivation is made in two steps: a formal one... Theoretical Population Biology journals http://www.medworm.com/rss/comments.php?id=2821493 Mon, 14 Sep 2009 23:00:00 +0100 2821493 http://www.medworm.com/index.php?rid=2810153&cid=s_36104_62_f&fid=36104&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D19761783%26dopt%3DAbstract Authors: Kelly CK, Bowler MG The impact on plants of herbivores and other pests varies greatly from year to year. Here we develop an analytical model of a temporal niche dynamic as a tool to examine how natural fluctuations in pest (enemy) levels may determine coexistence in competing annual plant species when one but not the other is affected by the pest. We show that the probability and speed with which the resistant drives out the sensitive species, coexists with it, or is driven out by its sensitive competitor depends on the cost of pest-resistance to the unaffected species, the frequency of high pest levels in the habitat and the competitive advantage of the sensitive species when the pest is not actively present. The interaction is regulated primarily by pest impact on relative s... Theoretical Population Biology journals http://www.medworm.com/rss/comments.php?id=2810153 Sun, 13 Sep 2009 23:00:00 +0100 2810153 http://www.medworm.com/index.php?rid=2804766&cid=s_36104_62_f&fid=36104&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D19751753%26dopt%3DAbstract Authors: Cressman R, Garay J A refuge model is developed for a single predator species and either one or two prey species where no predators are present in the prey refuge. An individual's fitness depends on its strategy choice or ecotype (predators decide which prey species to pursue and prey decide what proportion of their time to spend in the refuge) as well as on the population sizes of all three species. It is shown that, when there is a single prey species with a refuge or the two prey species with no refuge compete only indirectly (i.e. there is only apparent competition between prey species), that stable resident systems where all individuals in each species have the same ecotype cannot be destabilized by the introduction of mutant ecotypes that are initially selectively neutra... Theoretical Population Biology journals http://www.medworm.com/rss/comments.php?id=2804766 Thu, 10 Sep 2009 23:00:00 +0100 2804766 http://www.medworm.com/index.php?rid=2782381&cid=s_36104_62_f&fid=36104&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D19737575%26dopt%3DAbstract Authors: Zavala Sansón L, Provenzale A Plankton population dynamics in the upper layer of the ocean depends on upwelling processes that bring nutrients from deeper waters. In turn, these depend on the structure of the vertical velocity field. In coastal areas and in oceanic regions characterized by the presence of strong submarine topographic features, the variable bottom topography induces significant effects on vertical velocities and upwelling/downwelling patterns. As a consequence, large plankton and fish abundances are frequently observed above seamounts, canyons and steep continental shelves. In this work, the dynamics of an NPZ (nutrient-phytoplankton-zooplankton) system is numerically studied by coupling the ecosystem model with a quasi two-dimensional (2D) fluid model wit... Theoretical Population Biology journals http://www.medworm.com/rss/comments.php?id=2782381 Fri, 04 Sep 2009 23:00:00 +0100 2782381 http://www.medworm.com/index.php?rid=2782382&cid=s_36104_62_f&fid=36104&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D19735670%26dopt%3DAbstract Authors: Wagner BG, Earn DJ Viruses contained in live-attenuated virus vaccines (LAVV) can be transmitted between individuals, resulting in secondary or contact vaccinations. This fact has been exploited successfully in the use of the Oral Polio Vaccine (OPV) to better control wild-type polio viruses. In this work we analyze general LAVV vaccination models for infections that confer lifelong immunity. We consider both standard (continuous) vaccination strategies and pulse vaccination programs (where mass vaccination is carried out at regular intervals). For continuous vaccination, we provide a complete global analysis of a very general compartmental ordinary differential equation LAVV model. We find that the threshold vaccination level required for eradication of wild-type virus depend... Theoretical Population Biology journals http://www.medworm.com/rss/comments.php?id=2782382 Thu, 03 Sep 2009 23:00:00 +0100 2782382 http://www.medworm.com/index.php?rid=2734977&cid=s_36104_62_f&fid=36104&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D19703483%26dopt%3DAbstract Authors: Varughese MM The traditional Kolmogorov equations treat the size of a population as a discrete random variable. A model is introduced that extends these equations to incorporate environmental variability. Difficulties with this discrete model motivate approximating the population size as a continuous random variable through the use of diffusion processes. The set of cumulants for both the population size and the environmental factors affecting the population size characterize the population-environmental system. The evolution of this set, as predicted by the diffusion approximation, closely matches the corresponding predictions for the discrete model. It is also noted that the simulation estimates of the cumulants against which the predictions of the diffusion model are checke... Theoretical Population Biology journals http://www.medworm.com/rss/comments.php?id=2734977 Thu, 20 Aug 2009 23:00:00 +0100 2734977 http://www.medworm.com/index.php?rid=2712828&cid=s_36104_62_f&fid=36104&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D19682475%26dopt%3DAbstract Authors: Mari L, Gatto M, Casagrandi R We investigate how central-place seed foragers with a nest in the proximity of one or more seed sources determine the formation of different vegetation patterns. In particular, we discuss the ecological conditions that lead to the formation of hump-shaped (Janzen-Connell) patterns in a two-dimensional landscape. Our analysis shows that central-place predation can generate Janzen-Connell patterns even if predators' movement strategies are exclusively based on resource abundance, both in the single-plant/single-nest case and in a forest with several seed sources. We also show that social foraging may either promote or work against the formation of Janzen-Connell patterns, depending upon the way foragers take advantage of social interactions. PMI... Theoretical Population Biology journals http://www.medworm.com/rss/comments.php?id=2712828 Tue, 11 Aug 2009 23:00:00 +0100 2712828 http://www.medworm.com/index.php?rid=2702995&cid=s_36104_62_f&fid=36104&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D19679143%26dopt%3DAbstract Authors: Nagylaki T Evolution under the multilocus Levene model is investigated. The linkage map is arbitrary, but epistasis is absent. The geometric-mean fitness, w(rho), depends only on the vector of gene frequencies, rho; it is nondecreasing, and the single-generation change is zero only on the set, Lambda, of gametic frequencies at gene-frequency equilibrium. The internal gene-frequency equilibria are the stationary points of w(rho). If the equilibrium points rho^ of rho(t) (where t denotes time in generations) are isolated, as is generic, then rho(t) converges as t-->infinity to some rho^. Generically, rho(t) converges to a local maximum of w(rho). Write the vector of gametic frequencies, p, as (rho,d)(T), where d represents the vector of linkage disequilibria. If rho^ is a loc... Theoretical Population Biology journals http://www.medworm.com/rss/comments.php?id=2702995 Sun, 09 Aug 2009 23:00:00 +0100 2702995 http://www.medworm.com/index.php?rid=2696658&cid=s_36104_62_f&fid=36104&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D19664647%26dopt%3DAbstract Authors: Bürger R For the Levene model with soft selection in two demes, the maintenance of polymorphism at two diallelic loci is studied. Selection is nonepistatic and dominance is intermediate. Thus, there is directional selection in every deme and at every locus. We assume that selection is in opposite directions in the two demes because otherwise no polymorphism is possible. If at one locus there is no dominance, then a complete analysis of the dynamical and equilibrium properties is performed. In particular, a simple necessary and sufficient condition for the existence of an internal equilibrium and sufficient conditions for global asymptotic stability are obtained. These results are extended to deme-independent degree of dominance at one locus. A perturbation analysis establ... Theoretical Population Biology journals http://www.medworm.com/rss/comments.php?id=2696658 Mon, 03 Aug 2009 23:00:00 +0100 2696658 http://www.medworm.com/index.php?rid=2547181&cid=s_36104_62_f&fid=36104&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D19371755%26dopt%3DAbstract Authors: Bell AV, Rader RB, Peck SL, Sih A Spatial overlap between predators and prey is key to predicting their interaction strength and population dynamics. We constructed a spatially-explicit simulation model to explore how predator and prey behavioral traits and patterns of resource distribution influence spatial overlap between predators, prey, and prey resources. Predator and prey spatial association primarily followed the ideal free distribution. Departures from this model were intriguing, especially from the interactions of predator and prey behavior. When prey weakly avoided conspecifics, they associated more highly with resources when predators were present. Predators increased the rate of prey movement between patches, which increased their ability to sample their environmen... Theoretical Population Biology journals http://www.medworm.com/rss/comments.php?id=2547181 Sun, 28 Jun 2009 04:08:42 +0100 2547181 http://www.medworm.com/index.php?rid=2547178&cid=s_36104_62_f&fid=36104&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D19393256%26dopt%3DAbstract Authors: Kandler A, Laland KN In this paper we apply reaction-diffusion models to explore the relationship between the rate of behavioural innovation and the level of cultural diversity. We investigate how both independent invention and the modification and refinement of established innovations impact on cultural dynamics and diversity. Further, we analyse these relationships in the presence of biases in cultural learning and find that the introduction of new variants typically increases cultural diversity substantially in the short term, but may decrease long-term diversity. Independent invention generally supports higher levels of cultural diversity than refinement. Repeated patterns of innovation through refinement generate characteristic oscillating trends in diversity, with increa... Theoretical Population Biology journals http://www.medworm.com/rss/comments.php?id=2547178 Sun, 28 Jun 2009 04:08:36 +0100 2547178 http://www.medworm.com/index.php?rid=2547177&cid=s_36104_62_f&fid=36104&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D19426748%26dopt%3DAbstract Authors: Hou W, Liu T, Li Y, Li Q, Li J, Das K, Berg A, Wu R The structure and organization of natural plant populations can be understood by estimating the genetic parameters related to mating behavior, recombination frequency, and gene associations with DNA-based markers typed throughout the genome. We developed a statistical and computational model for estimating and testing these parameters from multilocus data collected in a natural population. This model, constructed by a maximum likelihood approach and implemented within the EM algorithm, is shown to be robust for simultaneously estimating the outcrossing rate, recombination frequencies and linkage disequilibria. The algorithm built with three or more markers allows the characterization of crossover interference in meiosis and h... Theoretical Population Biology journals http://www.medworm.com/rss/comments.php?id=2547177 Sun, 28 Jun 2009 04:08:34 +0100 2547177 http://www.medworm.com/index.php?rid=2547172&cid=s_36104_62_f&fid=36104&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D19486781%26dopt%3DAbstract Authors: Lehmann L, Rousset F Natural populations are of finite size and organisms carry multilocus genotypes. There are, nevertheless, few results on multilocus models when both random genetic drift and natural selection affect the evolutionary dynamics. In this paper we describe a formalism to calculate systematic perturbation expansions of moments of allelic states around neutrality in populations of constant size. This allows us to evaluate multilocus fixation probabilities (long-term limits of the moments) under arbitrary strength of selection and gene action. We show that such fixation probabilities can be expressed in terms of selection coefficients weighted by mean first passages times of ancestral gene lineages within a single ancestor. These passage times extend the coalescen... Theoretical Population Biology journals http://www.medworm.com/rss/comments.php?id=2547172 Sun, 28 Jun 2009 04:08:24 +0100 2547172 http://www.medworm.com/index.php?rid=2547163&cid=s_36104_62_f&fid=36104&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D19540865%26dopt%3DAbstract Authors: Lee CT, Puleston CO, Tuljapurkar S The population dynamics of preindustrial societies depend intimately on their surroundings, and food is a primary means through which environment influences population size and individual well-being. Food production requires labor; thus, dependence of survival and fertility on food involves dependence of a population's future on its current state. We use a perturbation approach to analyze the effects of random environmental variation on this nonlinear, age-structured system. We show that in expanding populations, direct environmental effects dominate induced population fluctuations, so environmental variability has little effect on mean hunger levels although it does decrease population growth. Growth rate determines the time until population... Theoretical Population Biology journals http://www.medworm.com/rss/comments.php?id=2547163 Wed, 17 Jun 2009 23:00:00 +0100 2547163 http://www.medworm.com/index.php?rid=2547164&cid=s_36104_62_f&fid=36104&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D19523479%26dopt%3DAbstract Authors: Guill C The population dynamics of a consumer population with an internal structure is investigated. The population is divided into juvenile and adult individuals that consume different resources and do not interfere with each other. Over a broad range of external conditions (varying mortality and different resource levels), alternative stable states exist. These population states correspond to domination of juveniles and domination of adults, respectively. When mortality is varied, hysteresis between the alternative states only occurs if juveniles have more resources than adults. In the opposite case the juvenile-dominated state is stable for all values of mortality, but the adult-dominated state is not. When the population is modelled with more than one juvenile stage, the a... Theoretical Population Biology journals http://www.medworm.com/rss/comments.php?id=2547164 Tue, 09 Jun 2009 23:00:00 +0100 2547164 http://www.medworm.com/index.php?rid=2547167&cid=s_36104_62_f&fid=36104&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D19501606%26dopt%3DAbstract Authors: Adams B, Sasaki A In models of pathogen interaction and evolution discrete genotypes in the form of bit strings may be mapped to points in a discrete phenotype space based on similarity in antigenic structure. Cross-immunity between strains, that is the reduction in susceptibility to strain A conferred to a host by infection with strain B, can then be defined for pairs of points in the antigenic space by a specified function. Analysis of an SIR type model shows that, if two strains are at equilibrium, the shape of the cross-immunity function has a strong influence on the invasion and coexistence of a third strain and, consequently, the expected evolutionary pathway. A function that is constant except for discontinuities at the end points is expected to result in the accumulati... Theoretical Population Biology journals http://www.medworm.com/rss/comments.php?id=2547167 Fri, 05 Jun 2009 23:00:00 +0100 2547167 http://www.medworm.com/index.php?rid=2547166&cid=s_36104_62_f&fid=36104&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D19501607%26dopt%3DAbstract Authors: Lion S, van Baalen M We study the evolution of a spatially structured population with two age classes using spatial moment equations. In the model, adults can either help juveniles by increasing their survival, or adopt a cannibalistic behaviour and consume juveniles. While cannibalism is the sole evolutionary outcome when the population is well-mixed, both cannibalism and parental care can be evolutionarily stable if the population is viscous. Our analysis allows us to make two main technical points. First, we present a method to define invasion fitness in class-structured viscous populations, which allows us to apply adaptive dynamics methodology. Second, we show that ordinary pair approximation introduces an important quantitative bias in the evolutionary model, even on ran... Theoretical Population Biology journals http://www.medworm.com/rss/comments.php?id=2547166 Fri, 05 Jun 2009 23:00:00 +0100 2547166 http://www.medworm.com/index.php?rid=2547165&cid=s_36104_62_f&fid=36104&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D19505487%26dopt%3DAbstract Authors: Higgins K Metapopulation extinction risk is the probability that all local populations are simultaneously extinct during a fixed time frame. Dispersal may reduce a metapopulation's extinction risk by raising its average per-capita growth rate. By contrast, dispersal may raise a metapopulation's extinction risk by reducing its average population density. Which effect prevails is controlled by habitat fragmentation. Dispersal in mildly fragmented habitat reduces a metapopulation's extinction risk by raising its average per-capita growth rate without causing any appreciable drop in its average population density. By contrast, dispersal in severely fragmented habitat raises a metapopulation's extinction risk because the rise in its average per-capita growth rate is more than offse... Theoretical Population Biology journals http://www.medworm.com/rss/comments.php?id=2547165 Fri, 05 Jun 2009 23:00:00 +0100 2547165 http://www.medworm.com/index.php?rid=2547168&cid=s_36104_62_f&fid=36104&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D19500610%26dopt%3DAbstract Authors: Li T, Anderson JJ A four-parameter model describing mortality as the first passage of an abstract measure of survival capacity, vitality, is developed and used to explore four classic problems in demography: (1) medfly demographic paradox, (2) effect of diet restriction on longevity, (3) cross-life stage effects on survival curves and (4) mortality plateaus. The model quantifies the sources of mortality in these classical problems into vitality-dependent and independent parts, and characterizes the vitality-dependent part in terms of initial and evolving heterogeneities. Three temporal scales express the balance of these factors: a time scale of death from senescence, a time scale of accidental mortality and a crossover time between evolving vs. initial heterogeneity. The exam... Theoretical Population Biology journals http://www.medworm.com/rss/comments.php?id=2547168 Tue, 02 Jun 2009 23:00:00 +0100 2547168 http://www.medworm.com/index.php?rid=2547183&cid=s_36104_62_f&fid=36104&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D19362099%26dopt%3DAbstract We describe a new approximate likelihood for population genetic data under a model in which a single ancestral population has split into two daughter populations. The approximate likelihood is based on the 'Product of Approximate Conditionals' likelihood and 'copying model' of Li and Stephens [Li, N., Stephens, M., 2003. Modeling linkage disequilibrium and identifying recombination hotspots using single-nucleotide polymorphism data. Genetics 165 (4), 2213-2233]. The approach developed here may be used for efficient approximate likelihood-based analyses of unlinked data. However our copying model also considers the effects of recombination. Hence, a more important application is to loosely-linked haplotype data, for which efficient statistical models explicitly featuring non-equilibrium pop... Theoretical Population Biology journals http://www.medworm.com/rss/comments.php?id=2547183 Sun, 31 May 2009 23:00:00 +0100 2547183 http://www.medworm.com/index.php?rid=2547182&cid=s_36104_62_f&fid=36104&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D19371754%26dopt%3DAbstract We present the results of computer simulations to support our heuristic mathematical results. We also present a more rigorous demonstration that the neutral conditional ancestral process converges to the Kingman coalescent in the limit as the mutation rate tends to infinity. PMID: 19371754 [PubMed - in process] (Source: Theoretical Population Biology) Theoretical Population Biology journals http://www.medworm.com/rss/comments.php?id=2547182 Sun, 31 May 2009 23:00:00 +0100 2547182 http://www.medworm.com/index.php?rid=2547180&cid=s_36104_62_f&fid=36104&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D19371756%26dopt%3DAbstract Authors: Ganapathy G, Uyenoyama MK Genomic survey data now permit an unprecedented level of sensitivity in the detection of departures from canonical evolutionary models, including expansions in population size and selective sweeps. Here, we examine the effects of seemingly subtle differences among sampling distributions on goodness of fit analyses of site frequency spectra constructed from single nucleotide polymorphisms. Conditioning on the observation of exactly two alleles in a random sample results in a site frequency spectrum that is independent of the scaled rate of neutral substitution (theta). Other sampling distributions, including conditioning on a single mutational event in the sample genealogy or randomly selecting a single mutation from a genealogy with multiple mutations... Theoretical Population Biology journals http://www.medworm.com/rss/comments.php?id=2547180 Sun, 31 May 2009 23:00:00 +0100 2547180 http://www.medworm.com/index.php?rid=2547179&cid=s_36104_62_f&fid=36104&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D19383508%26dopt%3DAbstract Authors: PMID: 19383508 [PubMed - in process] (Source: Theoretical Population Biology) Theoretical Population Biology journals http://www.medworm.com/rss/comments.php?id=2547179 Sun, 31 May 2009 23:00:00 +0100 2547179 http://www.medworm.com/index.php?rid=2547171&cid=s_36104_62_f&fid=36104&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D19496242%26dopt%3DAbstract Authors: Bodmer W In the 1960s Karlin and Bodmer established an active programme in mathematical population genetics with NIH support that, in turn, supported the work of Ewens and Feldman with Karlin. Subsequently Karlin established a similar programme in Israel. The overall contributions of Karlin to population genetics and molecular biology are briefly reviewed from a personal perspective. PMID: 19496242 [PubMed - in process] (Source: Theoretical Population Biology) Theoretical Population Biology journals http://www.medworm.com/rss/comments.php?id=2547171 Sun, 31 May 2009 23:00:00 +0100 2547171 http://www.medworm.com/index.php?rid=2547170&cid=s_36104_62_f&fid=36104&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D19496243%26dopt%3DAbstract Authors: Ewens WJ Sam Karlin's role in the development of the stochastic theory of evolutionary population genetics is outlined, together with his work in developing BLAST theory. PMID: 19496243 [PubMed - in process] (Source: Theoretical Population Biology) Theoretical Population Biology journals http://www.medworm.com/rss/comments.php?id=2547170 Sun, 31 May 2009 23:00:00 +0100 2547170 http://www.medworm.com/index.php?rid=2547169&cid=s_36104_62_f&fid=36104&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D19496244%26dopt%3DAbstract Authors: Nagylaki T The evolution of the gene frequencies at a single multiallelic locus under the joint action of migration and viability selection with dominance is investigated. The monoecious, diploid population is subdivided into finitely many panmictic colonies that exchange adult migrants independently of genotype. Underdominance and overdominance are excluded. If the degree of dominance is deme independent for every pair of alleles, then under the Levene model, the qualitative evolution of the gene frequencies (i.e., the existence and stability of the equilibria) is the same as without dominance. In particular: (i) the number of demes is a generic upper bound on the number of alleles present at equilibrium; (ii) there exists exactly one stable equilibrium, and it is globally at... Theoretical Population Biology journals http://www.medworm.com/rss/comments.php?id=2547169 Sun, 31 May 2009 23:00:00 +0100 2547169 http://www.medworm.com/index.php?rid=2547173&cid=s_36104_62_f&fid=36104&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D19464307%26dopt%3DAbstract Authors: Aguilée R, Claessen D, Lambert A The fixation of mutant alleles has been studied with models assuming various spatial population structures. In these models, the structure of the metapopulation that we call the "landscape" (number, size and connectivity of subpopulations) is often static. However, natural populations are subject to repetitive population size variations, fragmentation and secondary contacts at different spatiotemporal scales due to geological, climatic and ecological processes. In this paper, we examine how such dynamic landscapes can alter mutant fixation probability and time to fixation. We consider three stochastic landscape dynamics: (i) the population is subject to repetitive bottlenecks, (ii) to the repeated alternation of fragmentation and fusion of... Theoretical Population Biology journals http://www.medworm.com/rss/comments.php?id=2547173 Wed, 20 May 2009 23:00:00 +0100 2547173 http://www.medworm.com/index.php?rid=2547175&cid=s_36104_62_f&fid=36104&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D19433100%26dopt%3DAbstract Authors: Eriksson A, Mahjani B, Mehlig B We analyse sequential Markov coalescent algorithms for populations with demographic structure: for a bottleneck model, a population-divergence model, and for a two-island model with migration. The sequential Markov coalescent method is an approximation to the coalescent suggested by McVean and Cardin, and by Marjoram and Wall. Within this algorithm we compute, for two individuals randomly sampled from the population, the correlation between times to the most recent common ancestor and the linkage probability corresponding to two different loci with recombination rate R between them. These quantities characterise the linkage between the two loci in question. We find that the sequential Markov coalescent method approximates the coalescent well in ... Theoretical Population Biology journals http://www.medworm.com/rss/comments.php?id=2547175 Fri, 08 May 2009 23:00:00 +0100 2547175 http://www.medworm.com/index.php?rid=2547174&cid=s_36104_62_f&fid=36104&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D19433101%26dopt%3DAbstract Authors: Eldon B Structured coalescent processes are derived for the finite island model under a migration mechanism that conserves the subpopulation sizes. The underlying population model is a modified Moran model in which the reproducing individual can have very many offspring with some probability. Convergence to a structured coalescent process results when assuming that migration follows a coalescent timescale which can be much shorter than the usual Wright-Fisher timescale. Three different limit processes are possible depending on the coalescent timescale, two of which allow multiple mergers of ancestral lines. The expected time to most recent common ancestor, and the expected total size of the genealogy, of balanced and unbalanced samples can be very similar, even when migration ... Theoretical Population Biology journals http://www.medworm.com/rss/comments.php?id=2547174 Fri, 08 May 2009 23:00:00 +0100 2547174 http://www.medworm.com/index.php?rid=2547176&cid=s_36104_62_f&fid=36104&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D19427878%26dopt%3DAbstract Authors: Strimling P, Sjöstrand J, Enquist M, Eriksson K In a species capable of (imperfect) social learning, how much culture can a population of a given size carry? And what is the relationship between the individual and the population? In the first study of these novel questions, here we develop a mathematical model of the accumulation of independent cultural traits in a finite population with overlapping generations. PMID: 19427878 [PubMed - as supplied by publisher] (Source: Theoretical Population Biology) Theoretical Population Biology journals http://www.medworm.com/rss/comments.php?id=2547176 Thu, 07 May 2009 23:00:00 +0100 2547176 http://www.medworm.com/index.php?rid=2324104&cid=s_36104_62_f&fid=36104&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D19358861%26dopt%3DAbstract Authors: Benaïm M, Schreiber SJ Environmental fluctuations often have different impacts on individuals that differ in size, age, or spatial location. To understand how population structure, environmental fluctuations, and density-dependent interactions influence population dynamics, we provide a general theory for persistence for density-dependent matrix models in random environments. For populations with compensating density dependence, exhibiting "bounded" dynamics, and living in a stationary environment, we show that persistence is determined by the stochastic growth rate (alternatively, dominant Lyapunov exponent) when the population is rare. If this stochastic growth rate is negative, then the total population abundance goes to zero with probability one. If this stochastic gr... Theoretical Population Biology journals http://www.medworm.com/rss/comments.php?id=2324104 Mon, 06 Apr 2009 04:00:00 +0100 2324104 http://www.medworm.com/index.php?rid=2324107&cid=s_36104_62_f&fid=36104&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D19345237%26dopt%3DAbstract Authors: Samanta S, Li YJ, Weir BS The coancestry coefficient, also known as the population structure parameter, is of great interest in population genetics. It can be thought of as the intraclass correlation of pairs of alleles within populations and it can serve as a measure of genetic distance between populations. For a general class of evolutionary models it determines the distribution of allele frequencies among populations. Under more restrictive models it can be regarded as the probability of identity by descent of any pair alleles at a locus within a random mating population. In this paper we review estimation procedures that use the method of moments or are maximum likelihood under the assumption of normally distributed allele frequencies. We then consider the problem of testi... Theoretical Population Biology journals http://www.medworm.com/rss/comments.php?id=2324107 Wed, 01 Apr 2009 04:00:00 +0100 2324107 http://www.medworm.com/index.php?rid=2324113&cid=s_36104_62_f&fid=36104&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D19341750%26dopt%3DAbstract Authors: Etheridge AM, Griffiths RC A coalescent dual process for a multi-type Moran model with genic selection is derived using a generator approach. This leads to an expansion of the transition functions in the Moran model and the Wright-Fisher diffusion process limit in terms of the transition functions for the coalescent dual. A graphical representation of the Moran model (in the spirit of Harris) identifies the dual as a strong dual process following typed lines backwards in time. An application is made to the harmonic measure problem of finding the joint probability distribution of the time to the first loss of an allele from the population and the distribution of the surviving alleles at the time of loss. Our dual process mirrors the Ancestral Selection Graph of [Krone, S. M., N... Theoretical Population Biology journals http://www.medworm.com/rss/comments.php?id=2324113 Mon, 30 Mar 2009 04:00:00 +0100 2324113 http://www.medworm.com/index.php?rid=2324110&cid=s_36104_62_f&fid=36104&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D19341751%26dopt%3DAbstract Authors: M'gonigle LK, Shen JJ, Otto SP The rate at which mutations occur in nature is itself under natural selection. While a general reduction of mutation rates is advantageous for species inhabiting constant environments, higher mutation rates can be advantageous for those inhabiting fluctuating environments that impose on-going directional selection. Analogously, species involved in antagonistic co-evolutionary arms-races, such as hosts and parasites, can also benefit from higher mutation rates. We use modifier theory, combined with simulations, to investigate the evolution of mutation rate in such a host-parasite system. We derive an expression for the evolutionary stable mutation rate between two alleles, each of whose fitness depends on the current genetic composition of the oth... Theoretical Population Biology journals http://www.medworm.com/rss/comments.php?id=2324110 Mon, 30 Mar 2009 04:00:00 +0100 2324110 http://www.medworm.com/index.php?rid=2295600&cid=s_36104_62_f&fid=36104&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D19303892%26dopt%3DAbstract Authors: Gros A, Poethke HJ, Hovestadt T Inbreeding depression, asymmetries in costs or benefits of dispersal, and the mating system have been identified as potential factors underlying the evolution of sex-biased dispersal. We use individual-based simulations to explore how the mating system and demographic stochasticity influence the evolution of sex-specific dispersal in a metapopulation with females competing over breeding sites, and males over mating opportunities. Comparison of simulation results for random mating with those for a harem system (locally, a single male sires all offspring) reveal that even extreme variance in local male reproductive success (extreme male competition) does not induce male-biased dispersal. The latter evolves if between-patch variance in reproductive... Theoretical Population Biology journals http://www.medworm.com/rss/comments.php?id=2295600 Thu, 19 Mar 2009 04:00:00 +0100 2295600 http://www.medworm.com/index.php?rid=2295605&cid=s_36104_62_f&fid=36104&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D19303032%26dopt%3DAbstract Authors: Rowell JT Ecological modelers have long puzzled over the spatial distribution of species. The random walk or diffusive approach to dispersal has yielded important results for biology and mathematics, yet it has been inadequate in explaining all phenomenological features. Ranges can terminate non-smoothly absent a complementary shift in the characteristics of the environment. Also unexplained is the absence of a species from nearby areas of adequate, or even abundant, resources. In this paper, I show how local searching behavior - keyed to a density-dependent fitness - can limit the speed and extent of a species' spread. In contrast to standard diffusive processes, pseudo-rational movement facilitates the clustering of populations. It also can be used to estimate the speed of a... Theoretical Population Biology journals http://www.medworm.com/rss/comments.php?id=2295605 Tue, 17 Mar 2009 04:00:00 +0100 2295605 http://www.medworm.com/index.php?rid=2273071&cid=s_36104_62_f&fid=36104&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D19285994%26dopt%3DAbstract Authors: Weissman DB, Desai MM, Fisher DS, Feldman MW Complex traits often involve interactions between different genetic loci. This can lead to sign epistasis, whereby a set of mutations are individually deleterious or neutral but in combination confer a fitness benefit. In order to acquire the beneficial genotype, an asexual population must cross a fitness valley or plateau by first acquiring the deleterious or neutral intermediates. Here, we present a complete, intuitive theoretical description of the valley-crossing process across the full spectrum of possible parameter regimes. We calculate the rate at which a population crosses a fitness valley or plateau of arbitrary width, as a function of the mutation rates, the population size, and the fitnesses of the intermediates. We find ... Theoretical Population Biology journals http://www.medworm.com/rss/comments.php?id=2273071 Thu, 12 Mar 2009 04:00:00 +0100 2273071 http://www.medworm.com/index.php?rid=2273069&cid=s_36104_62_f&fid=36104&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D19285995%26dopt%3DAbstract Authors: Matessi C, Schneider KA We consider a model of frequency-dependent selection, to which we refer as the Wildcard Model. A variety of more specific models, representing quite diverse biological situations, are covered by the Wildcard Model as particular cases. Two very different particular models that are subsumed by the Wildcard Model are the game theoretically motivated two-phenotype model of Lessard (1984), and the model of selection on a continuous trait due to intraspecific competition of [Bürger, R., 2005. A multilocus analysis of intraspecific competition and stabilizing selection on a quantitative trait. J. Math. Biol. 50 (4) 355-396] and Schneider, K.A., 2006. A multilocus-multiallele analysis of frequency-dependent selection induced by intraspecific competition. J... Theoretical Population Biology journals http://www.medworm.com/rss/comments.php?id=2273069 Thu, 12 Mar 2009 04:00:00 +0100 2273069 http://www.medworm.com/index.php?rid=2257944&cid=s_36104_62_f&fid=36104&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D19275911%26dopt%3DAbstract Authors: Cobbold CA, Roland J, Lewis MA We investigate the effect of parasitoid phenology on host-parasitoid population cycles. Recent experimental research has shown that parasitised hosts can continue to interact with their unparasitised counterparts through competition. Parasitoid phenology, in particular the timing of emergence from the host, determines the duration of this competition. We construct a discrete-time host-parasitoid model in which within-generation dynamics associated with parasitoid timing is explicitly incorporated. We found that late-emerging parasitoids induce less severe, but more frequent, host outbreaks, independent of the choice of competition model. The competition experienced by the parasitised host reduces the parasitoids' numerical response to changes in ... Theoretical Population Biology journals http://www.medworm.com/rss/comments.php?id=2257944 Sat, 07 Mar 2009 05:00:00 +0100 2257944 http://www.medworm.com/index.php?rid=2257946&cid=s_36104_62_f&fid=36104&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D19269300%26dopt%3DAbstract Authors: Wilkinson RD, Tavaré S The fossil record provides a lower bound on the primate divergence time of 54.8 million years ago, but does not provide an explicit estimate for the divergence time itself. We show how the pattern of diversification through the Cenozoic can be combined with a model for speciation to give a distribution for the age of the primates. The primate fossil record, the number of extant primate species, and information about the structure of the primate phylogenetic tree are combined to provide an estimate for the joint distribution of the primate and anthropoid divergence times. To take this information into account, we derive the structure of the birth-and-death process conditioned to have a subtree originate at a particular point in time. This process has... Theoretical Population Biology journals http://www.medworm.com/rss/comments.php?id=2257946 Thu, 05 Mar 2009 05:00:00 +0100 2257946 http://www.medworm.com/index.php?rid=2257948&cid=s_36104_62_f&fid=36104&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D19268678%26dopt%3DAbstract Authors: Hamblin S, Hurd PL Sir Philip Sidney games are a widely used model of simple signaling. Johnstone and Grafen (Animal Behaviour 46:759-764, 1993) present a version in which the Evolutionarily Stable Strategy (ESS) is for most signalers to "honestly" signal, with a small minority of signalers who "cheat". This model is among the most frequently cited papers on the topic of "dishonest" signaling and supports the view that signals may be "dishonest" as long as they are "honest on average". Using genetic algorithms, we demonstrate that another solution exists to the game, an evolutionarily stable set of Nash equilibria in which members of the set never signal and all donors give their resource. Payoffs to players using this set of strategies is greater those when playing the "disho... Theoretical Population Biology journals http://www.medworm.com/rss/comments.php?id=2257948 Wed, 04 Mar 2009 05:00:00 +0100 2257948 http://www.medworm.com/index.php?rid=2234094&cid=s_36104_62_f&fid=36104&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D19249321%26dopt%3DAbstract Authors: Hobolth A, Wiuf C In this paper we consider the genealogy of two nested mutant alleles, assuming the constant-size neutral coalescent model with infinite sites mutation. We study the conditional genealogy and derive explicit formulas for the joint and marginal site frequency spectra for the double, single and zero mutant allele. In addition, we find the the mean ages of the two mutations. We show that the age of the youngest mutation does not depend on the frequency of the single mutant allele and that the frequency spectra for the single mutant allele and the zero mutant allele are the same. PMID: 19249321 [PubMed - as supplied by publisher] (Source: Theoretical Population Biology) Theoretical Population Biology journals http://www.medworm.com/rss/comments.php?id=2234094 Wed, 25 Feb 2009 05:00:00 +0100 2234094 http://www.medworm.com/index.php?rid=2234093&cid=s_36104_62_f&fid=36104&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D19249322%26dopt%3DAbstract Authors: Lessard S, Lahaie P The first-order effect of selection on the probability of fixation of an allele, with respect to an intensity of selection s>0 in a diploid population of fixed finite size N, undergoing discrete, nonoverlapping generations, is shown to be given by the sum of the average effects of that allele on the coefficient of selection in the current generation and all future generations, given the population state in the current generation. This projected average allelic effect is a weighted sum of average allelic effects in allozygous and autozygous offspring in the initial generation, with weights given in terms of expected coalescence times, under neutrality, for the lineages of two or three gametes chosen at random in the same generation. This is shown in the f... Theoretical Population Biology journals http://www.medworm.com/rss/comments.php?id=2234093 Wed, 25 Feb 2009 05:00:00 +0100 2234093 http://www.medworm.com/index.php?rid=2211514&cid=s_36104_62_f&fid=36104&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D19232526%26dopt%3DAbstract Authors: Pavoine S, Bonsall MB Rao's quadratic entropy (QE) is a diversity index that includes the abundances of categories (e.g. alleles, species) and distances between them. Here we show that, once the distances between categories are fixed, QE can be maximized with a reduced number of categories and by several different distributions of relative abundances of the categories. It is shown that Rao's coefficient of distance (DISC), based on QE, can equal zero between two maximizing distributions, even if they have no categories in common. The consequences of these findings on the relevance of QE for understanding biological diversity are evaluated in three case studies. The behaviour of QE at its maximum is shown to be strongly dependent on the distance metric. We emphasize that the st... Theoretical Population Biology journals http://www.medworm.com/rss/comments.php?id=2211514 Mon, 16 Feb 2009 05:00:00 +0100 2211514 http://www.medworm.com/index.php?rid=2138256&cid=s_36104_62_f&fid=36104&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D19167413%26dopt%3DAbstract Authors: Alvarez-Castro JM, Kopp M, Hermisson J We study a two-locus model of a quantitative trait with a continuum-of alleles and multilinear epistasis that evolves under mutation, selection, and genetic drift. We derive analytical results based on the so-called House of Gauss approximation for the genetic variance, the mean phenotype, and the mutational variance in the balance of the evolutionary forces. The analytical work is complemented by extensive individual-based computer simulations. We find that (1) analytical results are accurate in a large parameter space; (2) epistasis always reduces the equilibrium genetic variance, as predicted in earlier studies that exclude drift; (3) large-scale stochastic fluctuations and non-equilibrium phenomena like adaptive inertia can strongly i... Theoretical Population Biology journals http://www.medworm.com/rss/comments.php?id=2138256 Thu, 08 Jan 2009 05:00:00 +0100 2138256 http://www.medworm.com/index.php?rid=2101579&cid=s_36104_62_f&fid=36104&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D19136021%26dopt%3DAbstract Authors: Ross JV, Pagendam DE, Pollett PK Recently, a computationally-efficient method was presented for calibrating a wide-class of Markov processes from discrete-sampled abundance data. The method was illustrated with respect to one-dimensional processes and required the assumption of stationarity. Here we demonstrate that the approach may be directly extended to multi-dimensional processes, and two analogous computationally-efficient methods for non-stationary processes are developed. These methods are illustrated with respect to disease and population models, including application to infectious count data from an outbreak of "Russian influenza" (A/USSR/1977 H1N1) in an educational institution. The methodology is also shown to provide an efficient, simple and yet rigorous approach t... Theoretical Population Biology journals http://www.medworm.com/rss/comments.php?id=2101579 Sat, 03 Jan 2009 05:00:00 +0100 2101579 http://www.medworm.com/index.php?rid=2101580&cid=s_36104_62_f&fid=36104&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D19136020%26dopt%3DAbstract Authors: Eskola HT In this paper, we study the evolution of the per capita rate of reproduction as a function of time in the modelling framework introduced by Eskola and Geritz [Eskola, H.T.M., Geritz, S.A.H., 2007. On the mechanistic derivation of various discrete-time population models, Bull. Math. Biol. 69, 329-346]. We assume that the total number of juveniles one adult individual can produce is a finite constant, and we study how this number should be distributed during the season, when certain interaction and mortality processes are also included in the model. If aggressive interactions between the juveniles are not included in the model, evolution is simply optimizing, and the optimal reproductive strategy is always a single Dirac delta-peak within the season. If aggressive inte... Theoretical Population Biology journals http://www.medworm.com/rss/comments.php?id=2101580 Wed, 31 Dec 2008 05:00:00 +0100 2101580 http://www.medworm.com/index.php?rid=2075184&cid=s_36104_62_f&fid=36104&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D19116159%26dopt%3DAbstract Authors: Babak P, He F In this paper a spatially implicit neutral model for explaining the edge effects between habitats is proposed. To analyze this model we use two different approaches: a discrete approach that is based on the Master equation for a one step jump process and a continuous approach based on the approximation of the discrete jump process with the Kolmogorov-Fokker-Planck forward and backward equations. The discrete and continuous approaches are applied to analyze the species abundance distributions and the time to species extinction. Moreover, with the aid of the continuous approach a realistic classification of the behavior of species in local communities is developed. The species abundance dynamics at the edge between two distinct habitats is compared with those locat... Theoretical Population Biology journals http://www.medworm.com/rss/comments.php?id=2075184 Tue, 09 Dec 2008 05:00:00 +0100 2075184 http://www.medworm.com/index.php?rid=2075185&cid=s_36104_62_f&fid=36104&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D19116158%26dopt%3DAbstract Authors: Roy S Without the top-down effects and the external/physical forcing, a stable coexistence of two phytoplankton species under a single resource is impossible - a result well known from the principle of competitive exclusion. Here I demonstrate by analysis of a mathematical model that such a stable coexistence in a homogeneous media without any external factor would be possible, at least theoretically, provided (i) one of the two species is toxin producing thereby has an allelopathic effect on the other, and (ii) the allelopathic effect exceeds a critical level. The threshold level of allelopathy required for the coexistence has been derived analytically in terms of the parameters associated with the resource competition and the nutrient recycling. That the extra mortality of a... Theoretical Population Biology journals http://www.medworm.com/rss/comments.php?id=2075185 Sun, 07 Dec 2008 05:00:00 +0100 2075185 http://www.medworm.com/index.php?rid=2065690&cid=s_36104_62_f&fid=36104&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D19105968%26dopt%3DAbstract Authors: Lubben J, Boeckner D, Rebarber R, Townley S, Tenhumberg B We consider discrete time linear population models of the form n(t+1)=An(t) where A is a population projection matrix or integral projection operator, and n(t) represents a structured population at time t. It is well known that the asymptotic growth or decay rate of n(t) is determined by the leading eigenvalue of A. In practice, population models have substantial parameter uncertainty, and it might be difficult to quantify the effect of this uncertainty on the leading eigenvalue. For a large class of matrices and integral operators A, we give sufficient conditions for an eigenvalue to be the leading eigenvalue. By preselecting the leading eigenvalue to be equal to 1, this allows us to easily identify, which combination ... Theoretical Population Biology journals http://www.medworm.com/rss/comments.php?id=2065690 Sun, 07 Dec 2008 05:00:00 +0100 2065690 http://www.medworm.com/index.php?rid=2047817&cid=s_36104_62_f&fid=36104&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D19071153%26dopt%3DAbstract Authors: Anazawa M This paper presents a framework in which various single-species discrete-time population models exhibiting the Allee effect are derived from first principles. Here, the Allee effect means a reduction in individual fitness at low population sizes. The derivation is based on the distribution of female and male individuals among discrete resource sites, in addition to competitive and cooperative interaction among individuals. These derivations show how the derived population models depend on the type and the intensity of competition, and the degree of clustering of individuals. Along with these models exhibiting the Allee effect, this paper also presents first-principles derivation of population models without the Allee effect which include a parameter relating to the i... Theoretical Population Biology journals http://www.medworm.com/rss/comments.php?id=2047817 Wed, 19 Nov 2008 05:00:00 +0100 2047817 http://www.medworm.com/index.php?rid=1999402&cid=s_36104_62_f&fid=36104&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D19038278%26dopt%3DAbstract Authors: Meng C, Kubatko LS The application of phylogenetic inference methods, to data for a set of independent genes sampled randomly throughout the genome, often results in substantial incongruence in the single-gene phylogenetic estimates. Among the processes known to produce discord between single-gene phylogenies, two of the best studied in a phylogenetic context are hybridization and incomplete lineage sorting. Much recent attention has focused on the development of methods for estimating species' phylogenies in the presence of incomplete lineage sorting, but phylogenetic models that allow for hybridization have been more limited. Here we propose a model that allows incongruence in single-gene phylogenies to be due to both hybridization and incomplete lineage sorting, with the go... Theoretical Population Biology journals http://www.medworm.com/rss/comments.php?id=1999402 Wed, 05 Nov 2008 05:00:00 +0100 1999402 http://www.medworm.com/index.php?rid=1952475&cid=s_36104_62_f&fid=36104&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D18996138%26dopt%3DAbstract Authors: Sella G Because nearly neutral substitutions are thought to contribute substantially to molecular evolution, and much of our insight about the workings of nearly neutral evolution relies on theory, solvable models of this process are of particular interest. Here, I present an analytical method for solving models of nearly neutral evolution at steady state. The steady state solution applies to any constant fitness landscape under a dynamic of successive fixations, each of which occurs on the background of the population's most recent common ancestor. Because this dynamic neglects the effects of polymorphism in the population beyond the mutant allele under consideration, the steady state solution provides a decent approximation of evolutionary dynamics when the population mutati... Theoretical Population Biology journals http://www.medworm.com/rss/comments.php?id=1952475 Sat, 01 Nov 2008 04:00:00 +0100 1952475 http://www.medworm.com/index.php?rid=1926777&cid=s_36104_62_f&fid=36104&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D18957303%26dopt%3DAbstract Authors: Kouyos RD, Salathé M, Otto SP, Bonhoeffer S Antagonistic coevolution between hosts and parasites is known to affect selection on recombination in hosts. The Red Queen Hypothesis (RQH) posits that genetic shuffling is beneficial for hosts because it quickly creates resistant genotypes. Indeed, a large body of theoretical studies have shown that for many models of the genetic interaction between host and parasite, the coevolutionary dynamics of hosts and parasites generate selection for recombination or sexual reproduction. Here we investigate models in which the effect of the host on the parasite (and vice versa) depend approximately multiplicatively on the number of matched alleles. Contrary to expectation, these models generate a dynamical behavior that strongly selects ... Theoretical Population Biology journals http://www.medworm.com/rss/comments.php?id=1926777 Tue, 14 Oct 2008 04:00:00 +0100 1926777 http://www.medworm.com/index.php?rid=1895725&cid=s_36104_62_f&fid=36104&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D18938191%26dopt%3DAbstract Authors: Aoki K, Nakahashi W We study the effects of natural selection and migration on the numbers of individual learners and social learners in subdivided populations that occupy environmentally heterogeneous sites. The island model and the circular stepping model each have four classes of globally stable equilibria (fixation of individual learners, polymorphism of individual and social learners, fixation of social learners, and extinction). The linear stepping stone model has an additional class of equilibria, which are characterized by the complete absence of phenotypes adapted to the interior sites. Low and high rates of migration favor social and individual learners, respectively, in all three models. In addition, we use the stepping stone models to study the range expansion of a... Theoretical Population Biology journals http://www.medworm.com/rss/comments.php?id=1895725 Sat, 04 Oct 2008 04:00:00 +0100 1895725 http://www.medworm.com/index.php?rid=1880316&cid=s_36104_62_f&fid=36104&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D18851986%26dopt%3DAbstract Authors: Provorov NA, Vorobyov NI The mathematical model for evolution of the plant-microbe facultative mutualistic interactions based on the partners' symbiotic feedbacks is constructed. Using the example of rhizobia-legume symbiosis, we addressed these feedbacks in terms of the metabolic (C<-->N) exchange resulting in the parallel improvements of the partners' fitness (positive feedbacks). These improvements are correlated to the symbiotic efficiency dependent on the ratio of N(2)-fixing bacterial strains ("genuine mutualists") to the non- N(2)-fixing strains ("symbiotic cheaters") in the root nodules. The computer experiments demonstrated that an interplay between the frequency-dependent selection (FDS) and the Darwinian (frequency-independent) selection pressures implemented ... Theoretical Population Biology journals http://www.medworm.com/rss/comments.php?id=1880316 Thu, 02 Oct 2008 04:00:00 +0100 1880316 http://www.medworm.com/index.php?rid=1863208&cid=s_36104_62_f&fid=36104&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D18840456%26dopt%3DAbstract Authors: Hoyle A, Bowers RG Traditionally, to determine the possible evolutionary behaviour of an ecological system using adaptive dynamics, it is necessary to calculate the fitness and its derivatives at a singular point. We investigate the claim that the possible evolutionary behaviour can be predicted directly from the population dynamics, without the need for calculation, by applying three criteria - one based on the form of the density dependent rates and two on the role played by the evolving parameters. Taking a general continuous time model, with broad ecological range, we show that the claim is true. Initially, we assume that individuals enter in class 1 and move through population classes sequentially; later we relax these assumptions and find that the criteria still apply. H... Theoretical Population Biology journals http://www.medworm.com/rss/comments.php?id=1863208 Tue, 23 Sep 2008 04:00:00 +0100 1863208 http://www.medworm.com/index.php?rid=1856542&cid=s_36104_62_f&fid=36104&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D18835288%26dopt%3DAbstract Authors: Parsons TL, Quince C, Plotkin JB We study a generalisation of Moran's population-genetic model that incorporates density dependence. Rather than assuming fixed population size, we allow the number of individuals to vary stochastically with the same events that change allele number, according to a logistic growth process with density dependent mortality. We analyse the expected time to absorption and fixation in the 'quasi-neutral' case: both types have the same carrying capacity, achieved through a trade-off of birth and death rates. Such types would be competitively neutral in a classical, fixed-population Wright-Fisher model. Nonetheless, we find that absorption times are skewed compared to the Wright-Fisher model. The absorption time is longer than the Wright-Fisher predict... Theoretical Population Biology journals http://www.medworm.com/rss/comments.php?id=1856542 Thu, 18 Sep 2008 04:00:00 +0100 1856542 http://www.medworm.com/index.php?rid=1833527&cid=s_36104_62_f&fid=36104&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D18817799%26dopt%3DAbstract In this study we investigate rates of coalescence for X-linked and autosomal lineages in an island model with different population sizes and migration rates for males and females, obtaining the mean time to coalescence for pairs of lineages from the same deme and for pairs of lineages from different demes. We apply our results to microsatellite data from the Human Genome Diversity Panel, and we examine the male and female migration rates implied by observed F(ST) values. PMID: 18817799 [PubMed - as supplied by publisher] (Source: Theoretical Population Biology) Theoretical Population Biology journals http://www.medworm.com/rss/comments.php?id=1833527 Thu, 04 Sep 2008 04:00:00 +0100 1833527 http://www.medworm.com/index.php?rid=1815970&cid=s_36104_62_f&fid=36104&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D18804485%26dopt%3DAbstract Authors: Whigham PA, Dick GC, Spencer HG Genetic drift in finite populations ultimately leads to the loss of genetic variation. This paper examines the rate of neutral gene loss for a range of population structures defined by graph. We show that, where individuals reside at fixed points on an undirected graph with equal degree nodes, the mean time to loss differs from the panmictic value by a positive additive term that depends on the number of individuals (not genes) in the population. The effect of these spatial structures is to slow the time to fixation by an amount that depends on the way individuals are distributed, rather than changing the apparent number of genes available to be sampled. This relationship breaks down, however, for a broad class of spatial structures such as rand... Theoretical Population Biology journals http://www.medworm.com/rss/comments.php?id=1815970 Thu, 04 Sep 2008 04:00:00 +0100 1815970 http://www.medworm.com/index.php?rid=1769359&cid=s_36104_62_f&fid=36104&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D18768147%26dopt%3DAbstract Authors: Abta R, Schiffer M, Ben-Ishay A, Shnerb NM The stability of population oscillations in ecological systems is considered. Experiments suggest that in many cases the single patch dynamics of predator-prey or host-parasite systems is extinction prone, and stability is achieved only when the spatial structure of the population is expressed via desynchronization between patches. A few mechanisms have been suggested so far to explain the inability of dispersal to synchronize the system. Here we compare a recently discovered mechanism, based on the dependence of the angular velocity on the oscillation amplitude, with other, already known conditions for desynchronization. Using a toy model composed of diffusively coupled oscillators we suggest a classification scheme for stability mec... Theoretical Population Biology journals http://www.medworm.com/rss/comments.php?id=1769359 Wed, 20 Aug 2008 04:00:00 +0100 1769359 http://www.medworm.com/index.php?rid=1747094&cid=s_36104_62_f&fid=36104&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D18723039%26dopt%3DAbstract Authors: Schneider KA In this article we study the one-locus two-allele version of the pairwise-interaction model of frequency-dependent selection in discrete and continuous time. Our main aim is to provide necessary and sufficient conditions for the validity of maximization principles. We provide a systematic approach that covers all possible facets of the dynamical behavior of the model, and we illustrate our results by concrete examples. We show that the mean fitness of the population is nondecreasing if the interaction coefficients are symmetric and positive. Moreover, monotonic convergence to the set of equilibria always occurs, which is not true if we also consider negative interaction coefficients. For asymmetric interaction, we provide necessary conditions when the mean fitness... Theoretical Population Biology journals http://www.medworm.com/rss/comments.php?id=1747094 Thu, 07 Aug 2008 04:00:00 +0100 1747094 http://www.medworm.com/index.php?rid=1631730&cid=s_36104_62_f&fid=36104&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D18619389%26dopt%3DAbstract Authors: McCarthy D, Townley S, Hodgson D In this paper we present a simple method for identifying life-history perturbations in population projection matrices that yield an accelerating population growth rate. Accelerating growth means that the dependence of the growth rate on the perturbation is convex. Convexity, when the second sensitivity of the growth rate is positive, is calculated using a new formula derived from the transfer function of the perturbed system. This formula is used to explore the relationship between stasis and growth probabilities from stage-structured population projection matrices. PMID: 18619389 [PubMed - in process] (Source: Theoretical Population Biology) Theoretical Population Biology journals http://www.medworm.com/rss/comments.php?id=1631730 Thu, 17 Jul 2008 12:34:59 +0100 1631730 http://www.medworm.com/index.php?rid=1631729&cid=s_36104_62_f&fid=36104&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D18619390%26dopt%3DAbstract Authors: Lv Q, Schneider MK, Pitchford JW We study individual plant growth and size hierarchy formation in an experimental population of Arabidopsis thaliana, within an integrated analysis that explicitly accounts for size-dependent growth, size- and space-dependent competition, and environmental stochasticity. It is shown that a Gompertz-type stochastic differential equation (SDE) model, involving asymmetric competition kernels and a stochastic term which decreases with the logarithm of plant weight, efficiently describes individual plant growth, competition, and variability in the studied population. The model is evaluated within a Bayesian framework and compared to its deterministic counterpart, and to several simplified stochastic models, using distributional validation. We show th... Theoretical Population Biology journals http://www.medworm.com/rss/comments.php?id=1631729 Thu, 17 Jul 2008 12:34:57 +0100 1631729 http://www.medworm.com/index.php?rid=1631727&cid=s_36104_62_f&fid=36104&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D18621070%26dopt%3DAbstract Authors: Nakahashi W There are many examples of male mate choice for female traits that tend to be associated with high fertility. I develop quantitative genetic models of a female trait and a male preference to show when such a male preference can evolve. I find that a disagreement between the fertility maximum and the viability maximum of the female trait is necessary for directional male preference (preference for extreme female trait values) to evolve. Moreover, when there is a shortage of available male partners or variance in male nongenetic quality, strong male preference can evolve. Furthermore, I also show that males evolve to exhibit a stronger preference for females that are more feminine (less resemblance to males) than the average female when there is a sexual dimorphism c... Theoretical Population Biology journals http://www.medworm.com/rss/comments.php?id=1631727 Wed, 25 Jun 2008 04:00:00 +0100 1631727 http://www.medworm.com/index.php?rid=1631728&cid=s_36104_62_f&fid=36104&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D18619479%26dopt%3DAbstract Authors: Badham J, Abbass H, Stocker R Simulation is increasingly being used to examine epidemic behaviour and assess potential management options. The utility of the simulations rely on the ability to replicate those aspects of the social structure that are relevant to epidemic transmission. One approach is to generate networks with desired social properties. Recent research by Keeling and his colleagues has generated simulated networks with a range of properties, and examined the impact of these properties on epidemic processes occurring over the network. However, published work has included only limited analysis of the algorithm itself and the way in which the network properties are related to the algorithm parameters. This paper identifies some relationships between the algorithm p... Theoretical Population Biology journals http://www.medworm.com/rss/comments.php?id=1631728 Tue, 24 Jun 2008 04:00:00 +0100 1631728 http://www.medworm.com/index.php?rid=1582316&cid=s_36104_62_f&fid=36104&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D18598711%26dopt%3DAbstract We present a population model to examine the forces that determined the quality and quantity of human life in early agricultural societies where cultivable area is limited. The model is driven by the non-linear and interdependent relationships between the age distribution of a population, its behavior and technology, and the nature of its environment. The common currency in the model is the production of food, on which age-specific rates of birth and death depend. There is a single non-trivial equilibrium population at which productivity balances caloric needs. One of the most powerful controls on equilibrium hunger level is fertility control. Gains against hunger are accompanied by decreases in population size. Increasing worker productivity does increase equilibrium population size but d... Theoretical Population Biology journals http://www.medworm.com/rss/comments.php?id=1582316 Wed, 11 Jun 2008 04:00:00 +0100 1582316 http://www.medworm.com/index.php?rid=1554612&cid=s_36104_62_f&fid=36104&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D18572214%26dopt%3DAbstract Authors: Vanliere JM, Rosenberg NA Statistics for linkage disequilibrium (LD), the non-random association of alleles at two loci, depend on the frequencies of the alleles at the loci under consideration. Here, we examine the r(2) measure of LD and its mathematical relationship to allele frequencies, quantifying the constraints on its maximum value. Assuming independent uniform distributions for the allele frequencies of two biallelic loci, we find that the mean maximum value of r(2) is approximately 0.43051, and that r(2) can exceed a threshold of 4/5 in only approximately 14.232% of the allele frequency space. If one locus is assumed to have known allele frequencies-the situation in an association study in which LD between a known marker locus and an unknown trait locus is of interest... Theoretical Population Biology journals http://www.medworm.com/rss/comments.php?id=1554612 Sun, 01 Jun 2008 04:00:00 +0100 1554612 http://www.medworm.com/index.php?rid=1454914&cid=s_36104_62_f&fid=36104&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D18485981%26dopt%3DAbstract Authors: Iyer P, Roughgarden J Anisogamy refers to gametes that differ in size, and characterizes the difference between males and females. The evolution of aniosgamy is widely interpreted as involving conflict between gamete producers with small sperm parasitizing on the investment made by the eggs. Using a population genetic model for evolution at a locus that codes jointly for sperm and egg sizes of a hermaphrodite, we show that the origin of anisogamy in an externally spawning population need not involve conflict between gamete producers. Gamete size dimorphism may be an adaptation that increases gamete encounter rates when large zygotes are selected, and we show this in a mechanistically general individual selection model. We use the Vance survival function without specific allome... Theoretical Population Biology journals http://www.medworm.com/rss/comments.php?id=1454914 Tue, 20 May 2008 18:52:51 +0100 1454914 http://www.medworm.com/index.php?rid=1418618&cid=s_36104_62_f&fid=36104&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D18452961%26dopt%3DAbstract Faà di Bruno's formula and the distributions of random partitions in population genetics and physics. Theor Popul Biol. 2008 Mar 29; Authors: Hoppe FM We show that the formula of Faà di Bruno for the derivative of a composite function gives, in special cases, the sampling distributions in population genetics that are due to Ewens and to Pitman. The composite function is the same in each case. Other sampling distributions also arise in this way, such as those arising from Dirichlet, multivariate hypergeometric, and multinomial models, special cases of which correspond to Bose-Einstein, Fermi-Dirac, and Maxwell-Boltzmann distributions in physics. Connections are made to compound sampling models. PMID: 18452961 [PubMed - as supplied by publisher] (Source: Theoretical... Theoretical Population Biology journals http://www.medworm.com/rss/comments.php?id=1418618 Sat, 29 Mar 2008 04:00:00 +0100 1418618 http://www.medworm.com/index.php?rid=1410016&cid=s_36104_62_f&fid=36104&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D18442836%26dopt%3DAbstract Authors: Roze D, Rousset F Different methods have been developed to consider the effects of statistical associations among genes that arise in population genetics models: kin selection models deal with associations among genes present in different interacting individuals, while multilocus models deal with associations among genes at different loci. It was pointed out recently that these two types of models are very similar in essence. In this paper, we present a method to construct multilocus models in the infinite island model of population structure (where deme size may be arbitrarily small). This method allows one to compute recursions on allele frequencies, and different types of genetic associations (including associations between different individuals from the same deme), and inc... Theoretical Population Biology journals http://www.medworm.com/rss/comments.php?id=1410016 Sat, 22 Mar 2008 04:00:00 +0100 1410016 http://www.medworm.com/index.php?rid=1407398&cid=s_36104_62_f&fid=36104&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D18439637%26dopt%3DAbstract We present a demographic model that describes the feedbacks between food supply, human mortality and fertility rates, and labor availability in expanding populations, where arable land area is not limiting. This model provides a quantitative framework to describe how environment, technology, and culture interact to influence the fates of preindustrial agricultural populations. We present equilibrium conditions and derive approximations for the equilibrium population growth rate, food availability, and other food-dependent measures of population well-being. We examine how the approximations respond to environmental changes and to human choices, and find that the impact of environmental quality depends upon whether it manifests through agricultural yield or maximum (food-independent) surviva... Theoretical Population Biology journals http://www.medworm.com/rss/comments.php?id=1407398 Sat, 15 Mar 2008 04:00:00 +0100 1407398 http://www.medworm.com/index.php?rid=1387002&cid=s_36104_62_f&fid=36104&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D18420241%26dopt%3DAbstract Authors: Lehmann L, Feldman MW Limited migration results in kin selective pressure on helping behaviors under a wide range of ecological, demographic and life-history situations. However, such genetically determined altruistic helping can evolve only when migration is not too strong and group size is not too large. Cultural inheritance of helping behaviors may allow altruistic helping to evolve in groups of larger size because cultural transmission has the potential to markedly decrease the variance within groups and augment the variance between groups. Here, we study the co-evolution of culturally inherited altruistic helping behaviors and two alternative cultural transmission rules for such behaviors. We find that conformist transmission, where individuals within groups tend to copy ... Theoretical Population Biology journals http://www.medworm.com/rss/comments.php?id=1387002 Thu, 13 Mar 2008 04:00:00 +0100 1387002 http://www.medworm.com/index.php?rid=1361302&cid=s_36104_62_f&fid=36104&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D18395764%26dopt%3DAbstract Authors: Doncaster CP Time series of population density are often used to seek deviations from logistic regulation by testing for a non-linear decline in per capita growth rate with density. Here I show that this method fails when the interval between observations is not matched by the timing of density impacts on growth. Time series overestimate instantaneous density impacts at low density and underestimate them at high density. More generally, logistic growth produces a deterministically decelerating decline in per capita growth with density if the interval between measures of population size exceeds any lag in density response. Deceleration arises independently out of stochastic density fluctuations, and under-compensating regulation. These multiple influences lead to the conclusion... Theoretical Population Biology journals http://www.medworm.com/rss/comments.php?id=1361302 Tue, 04 Mar 2008 05:00:00 +0100 1361302 http://www.medworm.com/index.php?rid=1332808&cid=s_36104_62_f&fid=36104&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D18367223%26dopt%3DAbstract Authors: Andersen KH, Beyer JE, Pedersen M, Andersen NG, Gislason H The reproductive strategy of most fishes is to produce a large number of tiny eggs, leading to a huge difference between egg size and asymptotic body size. The viability of this strategy is examined by calculating the life-time reproductive success R(0) as a function of the asymptotic body size. A simple criterion for the optimality of producing small eggs is found, depending on the rate of predation relative to the specific rate of consumption. Secondly it is shown that the success of the reproductive strategy is increasing with asymptotic body size. Finally the existence of both upper and lower limits on the allowed asymptotic sizes is demonstrated. A metabolic upper limit to asymptotic body size for all higher anima... Theoretical Population Biology journals http://www.medworm.com/rss/comments.php?id=1332808 Sat, 16 Feb 2008 05:00:00 +0100 1332808 http://www.medworm.com/index.php?rid=1225742&cid=s_36104_62_f&fid=36104&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D18262579%26dopt%3DAbstract Authors: Peyrard N, Dieckmann U, Franc A Models of infectious diseases are characterized by a phase transition between extinction and persistence. A challenge in contemporary epidemiology is to understand how the geometry of a host's interaction network influences disease dynamics close to the critical point of such a transition. Here we address this challenge with the help of moment closures. Traditional moment closures, however, do not provide satisfactory predictions close to such critical points. We therefore introduce a new method for incorporating longer-range correlations into existing closures. Our method is technically simple, remains computationally tractable and significantly improves the approximation's performance. Our extended closures thus provide an innovative tool for ... Theoretical Population Biology journals http://www.medworm.com/rss/comments.php?id=1225742 Fri, 08 Feb 2008 05:00:00 +0100 1225742 http://www.medworm.com/index.php?rid=1208252&cid=s_36104_62_f&fid=36104&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D18241903%26dopt%3DAbstract Authors: Bolzoni L, De Leo GA, Gatto M, Dobson AP A number of wildlife pathogens are generalist and can affect different host species characterized by a wide range of body sizes. In this work we analyze the role of allometric scaling of host vital and epidemiological rates in a Susceptible-Exposed-Infected (SEI) model. Our analysis shows that the transmission coefficient threshold for the disease to establish in the population scales allometrically (exponent = 0.45) with host size as well as the threshold at which limit cycles occur. In contrast, the threshold of the basic reproduction number for sustained oscillations to occur is independent of the host size and is always greater than 5. In the case of rabies, we show that the oscillation periods predicted by the model match those obs... Theoretical Population Biology journals http://www.medworm.com/rss/comments.php?id=1208252 Wed, 30 Jan 2008 05:00:00 +0100 1208252 http://www.medworm.com/index.php?rid=1208253&cid=s_36104_62_f&fid=36104&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D18241902%26dopt%3DAbstract In this study, we investigate the evolutionary stability of the indirectly reciprocal strategy (discriminating strategy: DIS), which cooperates only with opponents who have good reputations, in n(>2)-person games where more than two individuals take part in a single group (interaction). We show that in n-person games, DIS is an evolutionarily stable strategy (ESS) even under the image-scoring reputation criterion, which is based only on first-order information and where cooperations (defections) are judged to be good (bad). This result is in contrast to that of 2-person games where DIS is not an ESS under reputation criteria based only on first-order information. PMID: 18241902 [PubMed - as supplied by publisher] (Source: Theoretical Population Biology) Theoretical Population Biology journals http://www.medworm.com/rss/comments.php?id=1208253 Sun, 23 Dec 2007 05:00:00 +0100 1208253 http://www.medworm.com/index.php?rid=1186145&cid=s_36104_62_f&fid=36104&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D18221762%26dopt%3DAbstract Authors: Nurmi T, Parvinen K We analyze the evolution of specialization in resource utilization in a discrete-time metapopulation model using the adaptive dynamics approach. The local dynamics in the metapopulation are based on the Beverton-Holt model with mechanistic underpinnings. The consumer faces a trade-off in the abilities to consume two resources that are spatially heterogeneously distributed to patches that are prone to local catastrophes. We explore the factors favoring the spread of generalist or specialist strategies. Increasing fecundity or decreasing catastrophe probability favors the spread of the generalist strategy and increasing environmental heterogeneity enlarges the parameter domain where the evolutionary branching is possible. When there are no catastrophes, incre... Theoretical Population Biology journals http://www.medworm.com/rss/comments.php?id=1186145 Sat, 15 Dec 2007 05:00:00 +0100 1186145 http://www.medworm.com/index.php?rid=1177946&cid=s_36104_62_f&fid=36104&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D18215408%26dopt%3DAbstract Authors: Liberman U, Feldman M Whether interaction between genes is better represented by synergistic or antagonistic epistasis has been a focus of experimental research in bacterial population genetics. Our previous research on evolution of modifiers of epistasis in diploid systems has indicated that the strength of positive or negative epistasis should increase provided linkage disequilibrium is maintained. Here we study a modifier of epistasis in fitness between two loci in a haploid system. Epistasis is modified in the neighborhood of a mutation-selection balance. We show that when linkage in the three-locus system is tight, an increase in the frequency of a modifier allele that induces either more negative or more positive epistasis is possible. Epistasis here can be measured on e... Theoretical Population Biology journals http://www.medworm.com/rss/comments.php?id=1177946 Fri, 14 Dec 2007 05:00:00 +0100 1177946 http://www.medworm.com/index.php?rid=1177948&cid=s_36104_62_f&fid=36104&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D18215406%26dopt%3DAbstract This article elucidates some of the conditions under which these transient near-extinctions are likely to occur. These conditions are given in terms of such geometric quantities as the position of the new coexistence state after an invasion, relative to the original coexistence state, and the severity of the post-invasion community's oscillations, as well as more directly biological quantities such as the demographic rates of the invader and the potential victim of a crash. Through graphical reasoning, numerical examples, and preliminary experimental results, the importance of these conditions is demonstrated. PMID: 18215406 [PubMed - as supplied by publisher] (Source: Theoretical Population Biology) Theoretical Population Biology journals http://www.medworm.com/rss/comments.php?id=1177948 Sat, 08 Dec 2007 05:00:00 +0100 1177948 http://www.medworm.com/index.php?rid=1177945&cid=s_36104_62_f&fid=36104&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D18215409%26dopt%3DAbstract Authors: Futschik A, Gach F We consider the estimation of the scaled mutation parameter theta, which is one of the parameters of key interest in population genetics. We provide a general result showing when estimators of theta can be improved using shrinkage when taking the mean squared error as the measure of performance. As a consequence, we show that Watterson's estimator is inadmissible, and propose an alternative shrinkage-based estimator that is easy to calculate and has a smaller mean squared error than Watterson's estimator for all possible parameter values 0<theta<infinity. This estimator is admissible in the class of all linear estimators. We then derive improved versions for other estimators of theta, including the MLE. We also investigate how an improvement can be obt... Theoretical Population Biology journals http://www.medworm.com/rss/comments.php?id=1177945 Sat, 08 Dec 2007 05:00:00 +0100 1177945 http://www.medworm.com/index.php?rid=1177944&cid=s_36104_62_f&fid=36104&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D18215410%26dopt%3DAbstract Authors: Tang S, Xiao Y, Cheke RA Host-parasitoid models including integrated pest management (IPM) interventions with impulsive effects at both fixed and unfixed times were analyzed with regard to host-eradication, host-parasitoid persistence and host-outbreak solutions. The host-eradication periodic solution with fixed moments is globally stable if the host's intrinsic growth rate is less than the summation of the mean host-killing rate and the mean parasitization rate during the impulsive period. Solutions for all three categories can coexist, with switch-like transitions among their attractors showing that varying dosages and frequencies of insecticide applications and the numbers of parasitoids released are crucial. Periodic solutions also exist for models with unfixed moments for... Theoretical Population Biology journals http://www.medworm.com/rss/comments.php?id=1177944 Sat, 08 Dec 2007 05:00:00 +0100 1177944 http://www.medworm.com/index.php?rid=1177947&cid=s_36104_62_f&fid=36104&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D18215407%26dopt%3DAbstract Authors: Jones D, Wakeley J We investigate the probabilities of identity-by-descent at three loci in order to find a signature which differentiates between the two types of crossing over events: recombination and gene conversion. We use a Markov chain to model coalescence, recombination, gene conversion and mutation in a sample of size two. Using numerical analysis, we calculate the total probability of identity-by-descent at the three loci, and partition these probabilities based on a partial ordering of coalescent events at the three loci. We use these results to compute the probabilities of four different patterns of conditional identity and non-identity at the three loci under recombination and gene conversion. Although recombination and gene conversion do make different prediction... Theoretical Population Biology journals http://www.medworm.com/rss/comments.php?id=1177947 Tue, 04 Dec 2007 05:00:00 +0100 1177947 http://www.medworm.com/index.php?rid=1140242&cid=s_36104_62_f&fid=36104&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D18179810%26dopt%3DAbstract Authors: Argasinski K, Kozłowski J The problem of density dependence appears in all approaches to the modelling of population dynamics. It is pertinent to classic models (i.e., Lotka-Volterra's), and also population genetics and game theoretical models related to the replicator dynamics. There is no density dependence in the classic formulation of replicator dynamics, which means that population size may grow to infinity. Therefore the question arises: How is unlimited population growth suppressed in frequency-dependent models? Two categories of solutions can be found in the literature. In the first, replicator dynamics is independent of background fitness. In the second type of solution, a multiplicative suppression coefficient is used, as in a logistic equation. Both approaches... Theoretical Population Biology journals http://www.medworm.com/rss/comments.php?id=1140242 Thu, 29 Nov 2007 05:00:00 +0100 1140242 http://www.medworm.com/index.php?rid=1137306&cid=s_36104_62_f&fid=36104&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D18178233%26dopt%3DAbstract Authors: Chu CY, Chien HK, Lee RD Mortality is U-shaped with age for many species, declining from birth to sexual maturity, then rising in adulthood, sometimes with postreproductive survival. We show analytically why the optimal life history of a species with determinate growth is likely to have this shape. An organism allocates energy among somatic growth, fertility and maintenance/survival at each age. Adults may transfer energy to juveniles, who can then use more energy than they produce. Optimal juvenile mortality declines from birth to maturity, either to protect the increasingly valuable cumulative investments by adults in juveniles or to exploit the compounding effects of early investment in somatic growth, since early growth raises subsequent energy production, which in turn su... Theoretical Population Biology journals http://www.medworm.com/rss/comments.php?id=1137306 Wed, 28 Nov 2007 05:00:00 +0100 1137306 http://www.medworm.com/index.php?rid=1063692&cid=s_36104_62_f&fid=36104&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D18048070%26dopt%3DAbstract Authors: Heffernan JM, Keeling MJ The epidemiology of acute infections is strongly influenced by the immune status of individuals. In-host models can provide quantitative predictions of immune status and can thus offer valuable insights into the factors that influence transmission between individuals and the effectiveness of vaccination protocols with respect to individual immunity. Here we develop an in-host model of measles infection. The model explicitly considers the effects of immune system memory and CD8 T-cells, which are key to measles clearance. The model is used to determine the effects of waning immunity through vaccination and infection, the effects of booster exposures or vaccines on the level of immunity, and the immune system characteristics that result in measles transm... Theoretical Population Biology journals http://www.medworm.com/rss/comments.php?id=1063692 Tue, 23 Oct 2007 04:00:00 +0100 1063692 http://www.medworm.com/index.php?rid=1041977&cid=s_36104_62_f&fid=36104&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D18023832%26dopt%3DAbstract Authors: Rouzine IM, Brunet E, Wilke CO We use traveling-wave theory to derive expressions for the rate of accumulation of deleterious mutations under Muller's ratchet and the speed of adaptation under positive selection in asexual populations. Traveling-wave theory is a semi-deterministic description of an evolving population, where the bulk of the population is modeled using deterministic equations, but the class of the highest-fitness genotypes, whose evolution over time determines loss or gain of fitness in the population, is given proper stochastic treatment. We derive improved methods to model the highest-fitness class (the stochastic edge) for both Muller's ratchet and adaptive evolution, and calculate analytic correction terms that compensate for inaccuracies which arise when t... Theoretical Population Biology journals http://www.medworm.com/rss/comments.php?id=1041977 Mon, 22 Oct 2007 04:00:00 +0100 1041977 http://www.medworm.com/index.php?rid=1033691&cid=s_36104_62_f&fid=36104&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D18006031%26dopt%3DAbstract Authors: Ihara Y Mathematical and simulation models of cultural transmission in a population where individuals may differ in their social status are developed. High-status individuals are assumed to be more influential to others but no more fertile or viable than low-status individuals. Analysis of the models suggests that culturally transmitted values, beliefs, and preferences that cause individuals to engage in prestige-seeking behavior can sometimes invade the population, even if that behavior reduces the net reproductive success of the prestige seekers. It is argued that some of the seemingly maladaptive behaviors observed in human societies may be a result of cultural evolution based on the human capacity for social learning, rather than a product of the "time lag" before the evol... Theoretical Population Biology journals http://www.medworm.com/rss/comments.php?id=1033691 Fri, 12 Oct 2007 04:00:00 +0100 1033691 http://www.medworm.com/index.php?rid=1033690&cid=s_36104_62_f&fid=36104&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D18006032%26dopt%3DAbstract Authors: Eames KT An epidemic spreading through a network of regular, repeated, contacts behaves differently from one that is spread by random interactions: regular contacts serve to reduce the speed and eventual size of an epidemic. This paper uses a mathematical model to explore the difference between regular and random contacts, considering particularly the effect of clustering within the contact network. In a clustered population random contacts have a much greater impact, allowing infection to reach parts of the network that would otherwise be inaccessible. When all contacts are regular, clustering greatly reduces the spread of infection; this effect is negated by a small number of random contacts. PMID: 18006032 [PubMed - as supplied by publisher] (Source: Theoretical Populat... Theoretical Population Biology journals http://www.medworm.com/rss/comments.php?id=1033690 Tue, 09 Oct 2007 04:00:00 +0100 1033690 http://www.medworm.com/index.php?rid=1015942&cid=s_36104_62_f&fid=36104&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D17988699%26dopt%3DAbstract Authors: Soubeyrand S, Enjalbert J, Sache I Variables with values in the circle or indexed by the circle have been studied in order to investigate questions in ecology, epidemiology, climatology and oceanography for example. To model circular variables with rough behaviors, the use of Gaussian random processes (GRPs) can be particularly convenient as will be seen in this paper. The roughness of a GRP being mainly determined by its correlation function, a circular correlation function convenient for rough processes is proposed. These mathematical tools are applied to describe the anisotropic spread of an airborne plant disease from a point source: a hierarchical model including two circular GRPs is built and used to analyze data coming from a field experiment. This random-effect model i... Theoretical Population Biology journals http://www.medworm.com/rss/comments.php?id=1015942 Sun, 07 Oct 2007 04:00:00 +0100 1015942 http://www.medworm.com/index.php?rid=1010703&cid=s_36104_62_f&fid=36104&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D17983636%26dopt%3DAbstract Authors: Lee AM, Engen S, Sæther BE Mechanisms generating inequalities among males in reproductive success are key to understanding the evolutionary significance of sexual selection. This paper develops a stochastic model to quantitatively describe and analyze mating systems on a continuous scale from strict monogamy to extreme polygyny. The variance in male mating success is shown to increase with increased differences among males, with decreased interdependence of mating events, with increased population size, and with an increased number of females per male. The latter condition decreases the opportunity for sexual selection. It is found that different combinations of mating system characteristics can lead to the same variance in male mating success, although the distribution d... Theoretical Population Biology journals http://www.medworm.com/rss/comments.php?id=1010703 Thu, 04 Oct 2007 04:00:00 +0100 1010703 http://www.medworm.com/index.php?rid=989991&cid=s_36104_62_f&fid=36104&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D17963807%26dopt%3DAbstract Authors: Hallatschek O, Nelson DR Large scale genomic surveys are partly motivated by the idea that the neutral genetic variation of a population may be used to reconstruct its migration history. However, our ability to trace back the colonization pathways of a species from their genetic footprints is limited by our understanding of the genetic consequences of a range expansion. Here, we study, by means of simulations and analytical methods, the neutral dynamics of gene frequencies in an asexual population undergoing a continual range expansion in one dimension. During such a colonization period, lineages can fix at the wave front by means of a "surfing" mechanism [Edmonds, C.A., Lillie, A.S., Cavalli-Sforza, L.L., 2004. Mutations arising in the wave front of an expanding population. P... Theoretical Population Biology journals http://www.medworm.com/rss/comments.php?id=989991 Wed, 19 Sep 2007 04:00:00 +0100 989991 http://www.medworm.com/index.php?rid=937263&cid=s_36104_62_f&fid=36104&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D17920093%26dopt%3DAbstract Authors: Rottenstreich S, Hamilton MB, Miller JR F(st) is a measure of genetic differentiation in a subdivided population. Sewall Wright observed that F(st)=11+2Nm in a haploid diallelic infinite island model, where N is the effective population size of each deme and m is the migration rate. In demonstrating this result, Wright relied on the infinite size of the population. Natural populations are not infinite and therefore they change over time due to genetic drift. In a finite population, F(st) becomes a random variable that evolves over time. In this work we ask, given an initial population state, what are the dynamics of the mean and variance of F(st) under the finite island model? In application both of these quantities are critical in the evaluation of F(st) data. We show that af... Theoretical Population Biology journals http://www.medworm.com/rss/comments.php?id=937263 Tue, 04 Sep 2007 04:00:00 +0100 937263 http://www.medworm.com/index.php?rid=851611&cid=s_36104_62_f&fid=36104&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D17573086%26dopt%3DAbstract Authors: Takimoto G, Miki T, Kagami M Intraguild predation is the simplest, ubiquitous form of trophic omnivory, known to greatly influence the structure and functioning of natural and managed food webs. Although alternative states are fundamental to intraguild predation dynamics, only necessary conditions for alternative states have been previously reported. Using simple models, we found complex but systematic patterns in which different alternative states occur along a productivity gradient, and clarified the sufficient conditions to separate these patterns. We found that two quantities known to control the necessary conditions also determine the sufficient conditions: (1) relative energy transfer efficiency through alternative trophic pathways to an intraguild predator, and (2) rela... Theoretical Population Biology journals http://www.medworm.com/rss/comments.php?id=851611 Sat, 01 Sep 2007 04:00:00 +0100 851611 http://www.medworm.com/index.php?rid=851609&cid=s_36104_62_f&fid=36104&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D17575994%26dopt%3DAbstract Authors: Hill WG, Weir BS An algorithm to predict the level of identity by descent simultaneously at multiple loci is presented, which can in principle be extended to any number of loci. The model assumes a random mating population, with random association of haplotypes. The relationship is shown between coefficients of multi-locus identity or non-identity by descent and moments of multi-locus linkage disequilibrium. Thus, these moments can be computed from the multilocus identity or, using algorithms derived previously to predict the disequilibria moments, vice-versa. The results can be applied to predict multi-locus identity in, for example, gene mapping. PMID: 17575994 [PubMed - in process] (Source: Theoretical Population Biology) Theoretical Population Biology journals http://www.medworm.com/rss/comments.php?id=851609 Sat, 01 Sep 2007 04:00:00 +0100 851609 http://www.medworm.com/index.php?rid=851608&cid=s_36104_62_f&fid=36104&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D17588629%26dopt%3DAbstract Authors: He D, Earn DJ Seasonal oscillations in birth rates are ubiquitous in human populations. These oscillations might play an important role in infectious disease dynamics because they induce seasonal variation in the number of susceptible individuals that enter populations. We incorporate seasonality of birth rate into the standard, deterministic susceptible-infectious-recovered (SIR) and susceptible-exposed-infectious-recovered (SEIR) epidemic models and identify parameter regions in which birth seasonality can be expected to have observable epidemiological effects. The SIR and SEIR models yield similar results if the infectious period in the SIR model is compared with the "infected period" (the sum of the latent and infectious periods) in the SEIR model. For extremely transmissi... Theoretical Population Biology journals http://www.medworm.com/rss/comments.php?id=851608 Sat, 01 Sep 2007 04:00:00 +0100 851608 http://www.medworm.com/index.php?rid=851607&cid=s_36104_62_f&fid=36104&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D17590399%26dopt%3DAbstract We present two approximations of the expected time to extinction in a population consisting of a small number of large sub-communities. These approximations are described for an SIR epidemic model, with focus on diseases with short infectious period in relation to life length, such as childhood diseases. Both approximations are based on Markov jump processes. Simulations indicate that the time to extinction is increasing in the degree of interaction between communities. This behaviour can also be seen in our approximations in relevant regions of the parameter space. PMID: 17590399 [PubMed - in process] (Source: Theoretical Population Biology) Theoretical Population Biology journals http://www.medworm.com/rss/comments.php?id=851607 Sat, 01 Sep 2007 04:00:00 +0100 851607 http://www.medworm.com/index.php?rid=851606&cid=s_36104_62_f&fid=36104&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D17624387%26dopt%3DAbstract Authors: Rottenstreich S, Miller JR, Hamilton MB We examine homozygosity and G(st) for a subdivided population governed by the finite island model. Assuming an infinite allele model and strong mutation we show that the steady state distributions of G(st) and homozygosity have asymptotic expansions in the mutation rate. We use this observation to derive asymptotic expansions for various moments of homozygosity and to derive rigorous formulas for the mean and variance of G(st). We show that G(st) approximately 1/(1+2Nm), similarly to the well known formula of Wright for the infinite island model, and that the variance of G(st) goes to zero as mutation increases. PMID: 17624387 [PubMed - in process] (Source: Theoretical Population Biology) Theoretical Population Biology journals http://www.medworm.com/rss/comments.php?id=851606 Sat, 01 Sep 2007 04:00:00 +0100 851606 http://www.medworm.com/index.php?rid=851605&cid=s_36104_62_f&fid=36104&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D17628624%26dopt%3DAbstract Authors: Gilad E, Shachak M, Meron E A mathematical model for plant communities in water-limited systems is introduced and applied to a mixed woody-herbaceous community. Two feedbacks between biomass and water are found to be of crucial importance for understanding woody-herbaceous interactions: water uptake by plants' roots and increased water infiltration at vegetation patches. The former acts to increase interspecific competition while the latter favors facilitation. The net interspecific interaction is determined by the relative strength of the two feedbacks. The model is used to highlight new mechanisms of plant-interaction change by studying factors that tilt the balance between the two feedbacks. Factors addressed in this study include environmental stresses and patch dynamics o... Theoretical Population Biology journals http://www.medworm.com/rss/comments.php?id=851605 Sat, 01 Sep 2007 04:00:00 +0100 851605 http://www.medworm.com/index.php?rid=851604&cid=s_36104_62_f&fid=36104&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D17643459%26dopt%3DAbstract Authors: Caliebe A, Neininger R, Krawczak M, Rösler U Let Z(n) denote the length of an external branch, chosen at random from a Kingman n-coalescent. Based on a recursion for the distribution of Z(n), we show that nZ(n) converges in distribution, as n tends to infinity, to a non-negative random variable Z with density xmapsto8/(2+x)(3), x0. This result facilitates the study of the time to the most recent common ancestor of a randomly chosen individual and its closest relative in a given population. This time span also reflects the maximum relatedness between a single individual and the rest of the population. Therefore, it measures the uniqueness of a random individual, a central characteristic of the genetic diversity of a population. PMID: 17643459 [PubMed - in process] (Sou... Theoretical Population Biology journals http://www.medworm.com/rss/comments.php?id=851604 Sat, 01 Sep 2007 04:00:00 +0100 851604 http://www.medworm.com/index.php?rid=851603&cid=s_36104_62_f&fid=36104&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D17658572%26dopt%3DAbstract Authors: Demon I, Haccou P, van den Bosch F Introgression is a key process in conservation biology, genetic modification of (crop) species and in the evolutionary ecology of many species. Here we consider the case of introgression of insecticide resistance in the whitefly, Bemisia tabaci. B. tabaci is a species complex consisting of a range of biotypes, known to have a high degree of inter-biotype reproductive isolation. In areas where insecticide resistant and susceptible biotypes of B. tabaci coexist, introgression of the resistance gene will have considerable consequences for whitefly control. Using a stochastic branching process model we calculate the relative importance of life-history traits in determining the probability of introgression given that a hybridization event has occu... Theoretical Population Biology journals http://www.medworm.com/rss/comments.php?id=851603 Sat, 01 Sep 2007 04:00:00 +0100 851603 http://www.medworm.com/index.php?rid=851602&cid=s_36104_62_f&fid=36104&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D17658573%26dopt%3DAbstract This study advances current knowledge about the impact of environmental colour using a trophic model (consumer-resource) experiencing environmental noise (temperature) in a biologically realistic manner-derived mechanistically from metabolic scaling theory. The model demonstrates that the variability of consumers and resources can respond differently to changing environmental colour, depending upon (i) their relative ability to track and over or undercompensate for environmental changes and (ii) the relative sensitivity of their equilibria to environmental changes. These results form the basis with which to interpret differences and facilitate comparisons of the variability of ecological communities across gradients of environmental colour. PMID: 17658573 [PubMed - in process] (Source:... Theoretical Population Biology journals http://www.medworm.com/rss/comments.php?id=851602 Sat, 01 Sep 2007 04:00:00 +0100 851602 http://www.medworm.com/index.php?rid=851601&cid=s_36104_62_f&fid=36104&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D17662324%26dopt%3DAbstract Authors: Dercole F, Gragnani A, Rinaldi S The aim of this paper is the study of the long-term behavior of population communities described by piecewise smooth models (known as Filippov systems). Models of this kind are often used to describe populations with selective switching between alternative habitats or diets or to mimic the evolution of an exploited resource where harvesting is forbidden when the resource is below a prescribed threshold. The analysis is carried out by performing the bifurcation analysis of the model with respect to two parameters. A relatively simple method, called the puzzle method, is proposed to construct the complete bifurcation diagram step-by-step. The method is illustrated through four examples concerning the exploitation and protection of interacting pop... Theoretical Population Biology journals http://www.medworm.com/rss/comments.php?id=851601 Sat, 01 Sep 2007 04:00:00 +0100 851601 http://www.medworm.com/index.php?rid=851649&cid=s_36104_62_f&fid=36104&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D17239909%26dopt%3DAbstract Authors: Song YS, Slatkin M The genealogical relationships of individuals in a finite population can create statistical non-independence of alleles at unlinked loci. In this paper, we introduce a flexible graphical method for computing the probabilities that two individuals in a finite, randomly mating population have the same haplotype or genotype at several loci. This method allows us to generalize the analysis of Laurie and Weir [2003. Dependency effects in multi-locus match probabilities. Theor. Popul. Biol. 63, 207-219] to cases with more loci and other models of mating. We show that monogamy increases the probabilities of genotypic matches at unlinked loci and that the effect of monogamy increases with the number L of loci. We conjecture a sharp upper bound on the effect of monog... Theoretical Population Biology journals http://www.medworm.com/rss/comments.php?id=851649 Wed, 01 Aug 2007 04:00:00 +0100 851649 http://www.medworm.com/index.php?rid=851648&cid=s_36104_62_f&fid=36104&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D17239910%26dopt%3DAbstract Authors: Parsons TL, Quince C We extend the one-locus two allele Moran model of fixation in a haploid population to the case where the total size of the population is not fixed. The model is defined as a two-dimensional birth-and-death process for allele number. Changes in allele number occur through density-independent death events and birth events whose per capita rate decreases linearly with the total population density. Uniquely for models of this type, the latter is determined by these same birth-and-death events. This provides a framework for investigating both the effects of fluctuation in total population number through demographic stochasticity, and deterministic density-dependent changes in mean density, on allele fixation. We analyze this model using a combination of asympto... Theoretical Population Biology journals http://www.medworm.com/rss/comments.php?id=851648 Wed, 01 Aug 2007 04:00:00 +0100 851648 http://www.medworm.com/index.php?rid=851647&cid=s_36104_62_f&fid=36104&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D17275866%26dopt%3DAbstract Authors: Vuilleumier S, Wilcox C, Cairns BJ, Possingham HP Disturbances affect metapopulations directly through reductions in population size and indirectly through habitat modification. We consider how metapopulation persistence is affected by different disturbance regimes and the way in which disturbances spread, when metapopulations are compact or elongated, using a stochastic spatially explicit model which includes metapopulation and habitat dynamics. We discover that the risk of population extinction is larger for spatially aggregated disturbances than for spatially random disturbances. By changing the spatial configuration of the patches in the system--leading to different proportions of edge and interior patches--we demonstrate that the probability of metapopulation extinction i... Theoretical Population Biology journals http://www.medworm.com/rss/comments.php?id=851647 Wed, 01 Aug 2007 04:00:00 +0100 851647 http://www.medworm.com/index.php?rid=851643&cid=s_36104_62_f&fid=36104&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D17296212%26dopt%3DAbstract Authors: Boukal DS, Sabelis MW, Berec L In Rosenzweig-MacArthur models of predator-prey dynamics, Allee effects in prey usually destabilize interior equilibria and can suppress or enhance limit cycles typical of the paradox of enrichment. We re-evaluate these conclusions through a complete classification of a wide range of Allee effects in prey and predator's functional response shapes. We show that abrupt and deterministic system collapses not preceded by fluctuating predator-prey dynamics occur for sufficiently steep type III functional responses and strong Allee effects (with unstable lower equilibrium in prey dynamics). This phenomenon arises as type III functional responses greatly reduce cyclic dynamics and strong Allee effects promote deterministic collapses. These collapses occ... Theoretical Population Biology journals http://www.medworm.com/rss/comments.php?id=851643 Wed, 01 Aug 2007 04:00:00 +0100 851643 http://www.medworm.com/index.php?rid=851642&cid=s_36104_62_f&fid=36104&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D17296213%26dopt%3DAbstract Authors: Tyvand PA, Thorvaldsen S An inhomogeneous discrete Markov model is formulated for sexual random mating with diploid male and female individuals. The generations are nonoverlapping and of given sizes. The genetic variation is in a sexually neutral allele with two varieties, giving three different genotypes. Taking sex as a marker, the Markov model works with six genotypes. The sex of each offspring is random. This implies a probability of extinction, giving the model an algorithmic nature. We compute expected genotype frequencies, their standard deviations and fixation probabilities. PMID: 17296213 [PubMed - in process] (Source: Theoretical Population Biology) Theoretical Population Biology journals http://www.medworm.com/rss/comments.php?id=851642 Wed, 01 Aug 2007 04:00:00 +0100 851642 http://www.medworm.com/index.php?rid=851641&cid=s_36104_62_f&fid=36104&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D17298838%26dopt%3DAbstract Authors: Curnow RN, Ayres KL An example of the evolution of the interacting behaviours of parents and progeny is studied using iterative equations linking the frequencies of the gametes produced by the progeny to the frequencies of the gametes in the parental generation. This population genetics approach shows that a model in which both behaviours are determined by a single locus can lead to a stable equilibrium in which the two behaviours continue to segregate. A model in which the behaviours are determined by genes at two separate loci leads eventually to fixation of the alleles at both loci but this can take many generations of selection. Models of the type described in this paper will be needed to understand the evolution of complex behaviour when genomic or experimental informatio... Theoretical Population Biology journals http://www.medworm.com/rss/comments.php?id=851641 Wed, 01 Aug 2007 04:00:00 +0100 851641 http://www.medworm.com/index.php?rid=851640&cid=s_36104_62_f&fid=36104&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D17298839%26dopt%3DAbstract Authors: Liu WC, Bonsall MB, Godfray HC Forest-insect systems frequently show cyclic dynamics which has been of considerable interest to both experimental and theoretical ecologists. One important issue has been the manner in which density-dependence acting on the host population through resource competition influences the likelihood of population cycles. Existing models make contradictory predictions. Here, we explore two models that allow different forms of density-dependence to be examined. We find that host density-dependence can influence the persistence of the host-pathogen interaction, the likelihood of population cycles and the stability of the host-pathogen interaction. In particular, over-compensatory density-dependence is likely to lead to host-pathogen cycles while under-co... Theoretical Population Biology journals http://www.medworm.com/rss/comments.php?id=851640 Wed, 01 Aug 2007 04:00:00 +0100 851640 http://www.medworm.com/index.php?rid=851634&cid=s_36104_62_f&fid=36104&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D17350060%26dopt%3DAbstract Authors: Serra MC, Haccou P We use multi-type Galton-Watson branching processes to model the evolution of populations that, due to a small reproductive ratio of the individuals, are doomed to extinction. Yet, mutations occurring during the reproduction process, may lead to the appearance of new types of individuals that are able to escape extinction. We provide examples of such populations in medical, biological and environmental contexts and give results on (i) the probability of escape/extinction, (ii) the distribution of the waiting time to produce the first individual whose lineage does not get extinct and (iii) the distribution of the time it takes for the number of mutants to reach a high level. Special attention is dedicated to the case where the probability of mutation is very ... Theoretical Population Biology journals http://www.medworm.com/rss/comments.php?id=851634 Wed, 01 Aug 2007 04:00:00 +0100 851634 http://www.medworm.com/index.php?rid=851625&cid=s_36104_62_f&fid=36104&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D17442355%26dopt%3DAbstract Authors: Nakahashi W Conformity is often observed in human social learning. Social learners preferentially imitate the majority or most common behavior in many situations, though the strength of conformity varies with the situation. Why has such a psychological tendency evolved? I investigate this problem by extending a standard model of social learning evolution with infinite environmental states (Feldman, M.W., Aoki, K., Kumm, J., 1996. Individual versus social learning: evolutionary analysis in a fluctuating environment. Anthropol. Sci. 104, 209-231) to include conformity bias. I mainly focus on the relationship between the strength of conformity bias that evolves and environmental stability, which is one of the most important factors in the evolution of social learning. Using the e... Theoretical Population Biology journals http://www.medworm.com/rss/comments.php?id=851625 Wed, 01 Aug 2007 04:00:00 +0100 851625 http://www.medworm.com/index.php?rid=851620&cid=s_36104_62_f&fid=36104&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D17467760%26dopt%3DAbstract Authors: Eskola HT, Parvinen K The Allee effect means reduction in individual fitness at low population densities. There are many discrete-time population models with an Allee effect in the literature, but most of them are phenomenological. Recently, Geritz and Kisdi [2004. On the mechanistic underpinning of discrete-time population models with complex dynamics. J. Theor. Biol. 228, 261-269] presented a mechanistic underpinning of various discrete-time population models without an Allee effect. Their work was based on a continuous-time resource-consumer model for the dynamics within a year, from which they derived a discrete-time model for the between-year dynamics. In this article, we obtain the Allee effect by adding different mate finding mechanisms to the within-year dynamics. Furt... Theoretical Population Biology journals http://www.medworm.com/rss/comments.php?id=851620 Wed, 01 Aug 2007 04:00:00 +0100 851620 http://www.medworm.com/index.php?rid=851619&cid=s_36104_62_f&fid=36104&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D17470373%26dopt%3DAbstract Authors: Nagylaki T, Lou Y The loss of a specified allele and the convergence of the gene frequencies at a single multiallelic locus under the joint action of migration and viability selection are investigated. The monoecious, diploid population is subdivided into finitely many panmictic colonies that exchange adult migrants independently of genotype. Sufficient conditions are established for global fixation and for global loss of a particular allele. When migration is either sufficiently weak or sufficiently strong relative to selection, the equilibria are described, convergence of the gene frequencies is demonstrated, and sufficient conditions for the increase of a suitably defined mean fitness are offered. If the selection pattern is the same in every colony and such that in a panmi... Theoretical Population Biology journals http://www.medworm.com/rss/comments.php?id=851619 Wed, 01 Aug 2007 04:00:00 +0100 851619 http://www.medworm.com/index.php?rid=851618&cid=s_36104_62_f&fid=36104&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D17481683%26dopt%3DAbstract Authors: Koszalka I, Bracco A, Pasquero C, Provenzale A Mathematical models used to represent plankton dynamics often display limit-cycle behavior in a range of realistic parameter values. However, experimental data do not show evidence of plankton oscillations besides externally driven seasonal blooms, casting doubts on the validity of the models themselves. In this work we show that spatial-temporal variability, coupled with advection by mesoscale turbulence, can disguise limit-cycle behavior to the point that it cannot be detected in fixed-point measurements of plankton abundance. The results presented here have more general implications as they indicate that the behavior of ecosystem models in the presence of advection can be very different from that occurring for homogeneous condi... Theoretical Population Biology journals http://www.medworm.com/rss/comments.php?id=851618 Wed, 01 Aug 2007 04:00:00 +0100 851618 http://www.medworm.com/index.php?rid=851617&cid=s_36104_62_f&fid=36104&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D17499323%26dopt%3DAbstract Authors: Snyder RE A population experiences environmental variation both directly, through effects on life history parameters such as fecundity, and indirectly, through effects on the population distributions of competitors and thus on the distribution of competition. Which spatial and temporal scales of environmental variation most influence the coexistence of two species thus depends in part on the degree to which the resident population responds to different scales of variation. In this paper, I calculate an approximation for a spatiotemporal population distribution as the result of a filter function convolved with the environmental variation. I find that there is no straightforward connection between spatial or temporal scales inherent to an organism's life history, such as mean li... Theoretical Population Biology journals http://www.medworm.com/rss/comments.php?id=851617 Wed, 01 Aug 2007 04:00:00 +0100 851617 http://www.medworm.com/index.php?rid=851615&cid=s_36104_62_f&fid=36104&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D17507068%26dopt%3DAbstract This study offers insight into the possible management strategies that involve manipulation of quality and supply level of additional food to predators, for the benefit of biological control. The theoretical conclusions agree with results of some practical biological control experiments. PMID: 17507068 [PubMed - in process] (Source: Theoretical Population Biology) Theoretical Population Biology journals http://www.medworm.com/rss/comments.php?id=851615 Wed, 01 Aug 2007 04:00:00 +0100 851615 http://www.medworm.com/index.php?rid=851614&cid=s_36104_62_f&fid=36104&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D17512565%26dopt%3DAbstract Authors: Drury KL Predicting crossings between stable states is a central issue in population biology. Crossings from low-density to high-density equilibria are often associated with pest outbreaks, while the opposite crossings are often associated with population collapse of harvested species. Here I use a simple, bistable model to demonstrate a technique for estimating mean first passage times (MFPT) of thresholds, including boundaries between stable equilibria. The approach is based on stochastic "shot-noise" perturbations to the population and the MFPTs compare favorably with mean crossing times from Monte Carlo numerical solutions of the stochastically perturbed model. This agreement suggests that MFPT approximations can be used to quantify expected effects of species manipulation... Theoretical Population Biology journals http://www.medworm.com/rss/comments.php?id=851614 Wed, 01 Aug 2007 04:00:00 +0100 851614 http://www.medworm.com/index.php?rid=851597&cid=s_36104_62_f&fid=36104&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D17727909%26dopt%3DAbstract Authors: Müller HG, Wang JL, Yu W, Delaigle A, Carey JR Information about the age distribution and survival of wild populations is of much interest in ecology and biodemography, but is hard to obtain. Established schemes such as capture-recapture often are not feasible. In the proposed residual demography paradigm, individuals are randomly sampled from the wild population at unknown ages and the resulting captive cohort is reared out in the laboratory until death. Under some basic assumptions one obtains a demographic convolution equation that involves the unknown age distribution of the wild population, the observed survival function of the captive cohort, and the observed survival function of a reference cohort that is independently raised in the laboratory from birth. We adopt ... Theoretical Population Biology journals http://www.medworm.com/rss/comments.php?id=851597 Sat, 28 Jul 2007 04:00:00 +0100 851597 http://www.medworm.com/index.php?rid=851596&cid=s_36104_62_f&fid=36104&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D17765277%26dopt%3DAbstract Authors: Mukandavire Z, Garira W This paper presents a sex-structured model for heterosexual transmission of HIV/AIDS in which the population is divided into three subgroups: susceptibles, infectives and AIDS cases. The subgroups are further divided into two classes, consisting of individuals involved in high-risk sexual activities and individuals involved in low-risk sexual activities. The model considers the movement of individuals from high to low sexual activity groups as a result of public health educational campaigns. Thus, in this case public health educational campaigns are resulting in the split of the population into risk groups. The equilibrium and epidemic threshold, which is known as the basic reproductive number (R(0)), are obtained, and stability (local and global) of th... Theoretical Population Biology journals http://www.medworm.com/rss/comments.php?id=851596 Fri, 27 Jul 2007 04:00:00 +0100 851596 http://www.medworm.com/index.php?rid=851598&cid=s_36104_62_f&fid=36104&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D17719617%26dopt%3DAbstract This article extends a stepping-stone model of pathogen evolution to include reservoir interactions. We demonstrate that the probability of a founding event culminating in an emerged pathogen can be significantly influenced by ongoing reservoir interactions. While infrequent reservoir interactions do not change the probability of disease emergence, moderately frequent interactions can promote emergence by facilitating adaptation to humans. Frequent reservoir interactions promote emergence even with minimal adaptation to humans. Thus, these results warn against perpetuated interaction between humans and animal reservoirs, as occurs when there are ecological or environmental changes that bring humans into more frequent contact with animal reservoirs. PMID: 17719617 [PubMed - as supplied ... Theoretical Population Biology journals http://www.medworm.com/rss/comments.php?id=851598 Wed, 25 Jul 2007 04:00:00 +0100 851598 http://www.medworm.com/index.php?rid=851599&cid=s_36104_62_f&fid=36104&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D17707873%26dopt%3DAbstract Authors: Britton T, Nordvik MK, Liljeros F We model a sexually transmitted infection in a network population where individuals have different numbers of partners, separated into steady and casual partnerships, where the risk of transmission is higher in steady partnerships. An individual's number of partners of the two types defines its degree, and the degrees in the community specify the degree distribution. For this structured network population a simple model for disease transmission is defined and the basic reproduction number R(0) is derived, R(0) being a size-biased (i.e. biasing individuals with many partners) average number of new infections caused by individuals during the early stages of the epidemic. First a homosexual population is considered and then a heterosexual populat... Theoretical Population Biology journals http://www.medworm.com/rss/comments.php?id=851599 Tue, 10 Jul 2007 04:00:00 +0100 851599 http://www.medworm.com/index.php?rid=851595&cid=s_36104_62_f&fid=36104&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D17804030%26dopt%3DAbstract This article appeals to computational and numerical methods to contrast the predictive power of the Malthusian and the entropic principles. The computational analysis rejects the Malthusian model and is consistent with of the entropic principle. These studies thus provide support for the general claim that entropy is the appropriate measure of Darwinian fitness and constitutes an evolutionary parameter with broad predictive and explanatory powers. PMID: 17804030 [PubMed - as supplied by publisher] (Source: Theoretical Population Biology) Theoretical Population Biology journals http://www.medworm.com/rss/comments.php?id=851595 Thu, 05 Jul 2007 04:00:00 +0100 851595