Pannell J R, Charlesworth B
Institute of Cell, Animal and Population Biology, University of Edinburgh, UK.
Philos Trans R Soc Lond B Biol Sci. 2000 Dec 29;355(1404):1851-64. doi: 10.1098/rstb.2000.0740.
Many species persist as a metapopulation under a balance between the local extinction of subpopulations or demes and their recolonization through dispersal from occupied patches. Here we review the growing body of literature dealing with the genetic consequences of such population turnover. We focus our attention principally on theoretical studies of a classical metapopulation with a 'finite-island' model of population structure, rather than on 'continent-island' models or 'source-sink' models. In particular, we concern ourselves with the subset of geographically subdivided population models in which it is assumed that all demes are liable to extinction from time to time and that all demes receive immigrants. Early studies of the genetic effects of population turnover focused on population differentiation, such as measured by F(ST). A key advantage of F(ST) over absolute measures of diversity is its relative independence of the mutation process, so that different genes in the same species may be compared. Another advantage is that F(ST) will usually equilibrate more quickly following perturbations than will absolute levels of diversity. However, because F(ST) is a ratio of between-population differentiation to total diversity, the genetic effects of metapopulation processes may be difficult to interpret in terms of F(ST) on its own, so that the analysis of absolute measures of diversity in addition is likely to be informative. While population turnover may either increase or decrease F(ST), depending on the mode of colonization, recurrent extinction and recolonization is expected always to reduce levels of both within-population and species-wide diversity (piS and piT, respectively). One corollary of this is that piS cannot be used as an unbiased estimate of the scaled mutation rate, theta, as it can, with some assumptions about the migration process, in species whose demes do not fluctuate in size. The reduction of piT in response to population turnover reflects shortened mean coalescent times, although the distribution of coalescence times under extinction colonization equilibrium is not yet known. Finally, we review current understanding of the effect of metapopulation dynamics on the effective population size.
许多物种以集合种群的形式存在，处于亚种群或deme的局部灭绝与通过从已占据斑块扩散实现再定殖之间的平衡状态。在此，我们综述了关于这种种群更替的遗传后果的不断增多的文献。我们主要关注具有“有限岛屿”种群结构模型的经典集合种群的理论研究，而非“大陆 - 岛屿”模型或“源 - 汇”模型。特别地，我们关注地理细分种群模型的一个子集，在该子集中假设所有deme都时有灭绝风险且所有deme都会接收移民。早期关于种群更替遗传效应的研究聚焦于种群分化，比如用F(ST)来衡量。F(ST)相对于绝对多样性度量的一个关键优势在于它相对独立于突变过程，这样同一物种的不同基因就可以进行比较。另一个优势是，与绝对多样性水平相比，F(ST)在受到扰动后通常会更快达到平衡。然而，由于F(ST)是种群间分化与总多样性的比值，仅依据F(ST)本身可能难以解释集合种群过程的遗传效应，所以此外对绝对多样性度量的分析可能也会提供有用信息。虽然种群更替可能会增加或降低F(ST)，这取决于定殖模式，但反复的灭绝和再定殖预计总会降低种群内和物种范围内的多样性水平（分别为piS和piT）。由此产生的一个推论是，piS不能像在deme大小不波动的物种中那样，在对迁移过程做一些假设的情况下，用作标度突变率theta的无偏估计。piT因种群更替而降低反映了平均合并时间缩短，尽管灭绝 - 定殖平衡下合并时间的分布尚不清楚。最后，我们综述了目前对集合种群动态对有效种群大小影响的理解。
