de Vries Charlotte, Caswell Hal
University of Amsterdam, Netherlands.
University of Amsterdam, Netherlands.
Theor Popul Biol. 2019 Dec;130:160-169. doi: 10.1016/j.tpb.2019.07.012. Epub 2019 Aug 1.
The outcome of natural selection depends on the demographic processes of birth, death, and development. Here, we derive conditions for protected polymorphism in a population characterized by age- or stage-dependent demography with two sexes. We do so using a novel two-sex matrix population model including basic Mendelian genetics (one locus, two alleles, random mating). Selection may operate on survival, growth, or fertility, any or all of which may differ between the sexes. The model can therefore incorporate genes with arbitrary pleiotropic and sex-specific effects. Conditions for protected polymorphism are expressed in terms of the eigenvalues of the linearization of the model at the homozygote boundary equilibria. We show that in the absence of sexual dimorphism, polymorphism requires heterozygote superiority in the genotypic population growth rate. In the presence of sexual dimorphism, however, heterozygote superiority is not required; an inferior heterozygote may invade, reducing the population growth rate and even leading to extinction (so-called evolutionary suicide). Our model makes no assumptions about separation of time scales between ecological and evolutionary processes, and can thus be used to project sex×stage×genotype dynamics of eco-evolutionary processes. Empirical evidence that sexual dimorphism affects extinction risk is growing, yet sex differences are often ignored in evolutionary demography and in eco-evolutionary models. Our analysis highlights the importance of sexual dimorphism and suggests mechanisms by which an allele can be favored by selection, yet drive a population to extinction, as a result of the structure and interdependence of sex- and stage-specific processes.
自然选择的结果取决于出生、死亡和发育的人口统计学过程。在此，我们推导了在具有两性且年龄或阶段依赖人口统计学特征的种群中受保护多态性的条件。我们通过一个新颖的两性矩阵种群模型来进行推导，该模型包括基本孟德尔遗传学（一个位点，两个等位基因，随机交配）。选择可作用于生存、生长或繁殖力，其中任何一个或所有方面在两性之间都可能不同。因此，该模型可以纳入具有任意多效性和性别特异性效应的基因。受保护多态性的条件以模型在纯合子边界平衡点处线性化的特征值来表示。我们表明，在不存在性二态性的情况下，多态性需要杂合子在基因型种群增长率方面具有优势。然而，在存在性二态性的情况下，并不需要杂合子具有优势；一个劣势杂合子可能会入侵，降低种群增长率甚至导致灭绝（所谓的进化自杀）。我们的模型没有对生态和进化过程之间的时间尺度分离做出假设，因此可用于预测生态进化过程的性别×阶段×基因型动态。有越来越多的经验证据表明性二态性会影响灭绝风险，但在进化人口统计学和生态进化模型中，性别差异往往被忽视。我们的分析突出了性二态性的重要性，并提出了一种机制，即由于性别和阶段特异性过程的结构和相互依存关系，一个等位基因可能受到选择青睐，但却会导致种群灭绝。
