Researches On Several Evolution Issues In An Age-structured Metapopulation By Simulation

In a metapopulation with recurrent local extinction and recolonization, every deme will have a "age" property. This recurrent population turnover can not only change the mean frequency of deleterious mutations, but also have an effect on the distribution of deleterious mutations across the whole metapopulation and the distribution of gentetic diversity among demes in the same and different ages. Although the effects of population turnover on average levels of genetic diversity among demes in a metapopulation have bean the focus of much attention, much less is know about the distribution of nonneutral genetic diversity among demes of different ages.In this paper, we studied the distribution of genetic load, within-deme inbreeding depression and heterosis in an age-structured metapopulation by simulation. We found that such distribution depended on the type of mutation involved:(1) for mildly deleterious mutations, within-deme inbreeding depression increased, whereas heterosis and genetic load decreased with deme age following severe colonization bottlenecks.(2) For recessive lethal alleles, it tended to be purged during colonization bottlenecks, with older populations showing higher genetic load and higher within-deme inbreeding depression; heterosis caused by recessive lethal alleles and resulted from gene flow among different demes tended to be greatest for young demes, because the mutations responsible tended to be purged in the first few generations after colonization, heterosis decreased.The genetic diversity among demes in the different ages may result in variation in migration rate among different demes. and affect the evolution of migration. Hence, we also investigated the evolution route of migration rates among demes in different ages with hard selection. We found that migration rate decreased as demes grew older. The distribution of migration rate among demes in different ages is consistent under different mutation rates for migration and migration costs. Migration rate increased with increases in mutation rates for migration and decreases in migrate costs.We conclude that there are differences in the distribution of genetic load, within-deme inbreeding depression and heterosis among demes of different ages in an age-structured metapopuation. These differences will have a profound effect on the evolution of a species’ dispersal and result in differences in the distribution of migration rates among demes of different ages. This suggests that, in future theoretical and experimental studies, there is the potential need for measuring these values (migration rate, within-deme inbreeding depression, genetic load etc.) in demes of different ages. Moreover, population genetic parameters might be given an indirect indication of the deme age in metapopualtions.