Université Montpellier 2, CNRS, Institut des Sciences de l'Évolution, UMR 5554 CC65, Montpellier cedex 05, France.
J Evol Biol. 2013 Jun;26(6):1185-202. doi: 10.1111/jeb.12132. Epub 2013 May 3.
How do mutation and gene flow influence population persistence, niche expansion and local adaptation in spatially heterogeneous environments? In this article, we analyse a demographic and evolutionary model of adaptation to an environment containing two habitats in equal frequencies, and we bridge the gap between different theoretical frameworks. Qualitatively, our model yields four qualitative types of outcomes: (i) global extinction of the population, (ii) adaptation to one habitat only, but also adaptation to both habitats with, (iii) specialized phenotypes or (iv) with generalized phenotypes, and we determine the conditions under which each equilibrium is reached. We derive new analytical approximations for the local densities and the distributions of traits in each habitat under a migration-selection-mutation balance, compute the equilibrium values of the means, variances and asymmetries of the local distributions of phenotypes, and contrast the effects of migration and mutation on the evolutionary outcome. We then check our analytical results by solving our model numerically, and also assess their robustness in the presence of demographic stochasticity. Although increased migration results in a decrease in local adaptation, mutation in our model does not influence the values of the local mean traits. Yet, both migration and mutation can have dramatic effects on population size and even lead to metapopulation extinction when selection is strong. Niche expansion, the ability for the population to adapt to both habitats, can also be prevented by small migration rates and a reduced evolutionary potential characterized by rare mutation events of small effects; however, niche expansion is otherwise the most likely outcome. Although our results are derived under the assumption of clonal reproduction, we finally show and discuss the links between our model and previous quantitative genetics models.
突变和基因流如何影响空间异质环境中种群的持久性、生态位扩张和局部适应？本文分析了一个适应包含两个栖息地的环境的人口和进化模型，并弥合了不同理论框架之间的差距。定性地，我们的模型产生了四种定性的结果类型：（i）种群的全球灭绝，（ii）仅适应一个栖息地，但也适应两个栖息地，（iii）专门的表型或（iv）具有广义表型，我们确定了每种平衡达到的条件。我们在迁移-选择-突变平衡下推导出局部密度和每个栖息地中特征分布的新解析近似值，计算表型局部分布的均值、方差和不对称性的平衡值，并对比迁移和突变对进化结果的影响。然后，我们通过数值求解模型来检查我们的分析结果，还评估了在存在人口统计随机性时的稳健性。尽管增加迁移会导致局部适应度降低，但在我们的模型中，突变不会影响局部特征的均值。然而，迁移和突变都可以对种群大小产生巨大影响，甚至在选择强烈时导致复合种群灭绝。生态位扩张，即种群适应两个栖息地的能力，也可能被小的迁移率和由小效应的罕见突变事件导致的降低的进化潜力所阻止；然而，否则，生态位扩张是最可能的结果。尽管我们的结果是在克隆繁殖的假设下得出的，但我们最终展示并讨论了我们的模型与先前的数量遗传学模型之间的联系。
