Phenotype-environment matching predicts both positive and negative effects of intraspecific variation

Natural populations can vary considerably in their genotypic and/or phenotypic diversity. Differences in this intraspecific diversity can have important consequences for contemporary ecological dynamics, but the direction and magnitude of these effects appear inconsistent across studies and systems. Here we proposed and tested the hypothesis that context-dependent ecological effects of altering phenotypic variance are predictable and arise from the relationship between a population’s mean phenotype and the local environmental optimum. By factorially manipulating the mean and variance of a key host trait in environments with and without a lethal parasite, we demonstrate that increasing phenotypic variance can have beneficial effects for host populations (e.g. smaller disease epidemics), but only when the population’s initial phenotype was poorly-matched to the local environment. When phenotypes were initially well-suited to environmental conditions, in contrast, greater phenotypic varian...自然种群的基因型多样性（genotypic diversity）与（或）表型多样性（phenotypic diversity）往往存在显著差异。这类种内多样性（intraspecific diversity）的差异会对当代生态动态产生重要影响，但此类效应的方向与强度在不同研究与系统中似乎并不一致。本研究提出并验证了一项假说：改变表型方差（phenotypic variance）所产生的环境依赖型生态效应具有可预测性，其根源在于种群平均表型与局部环境最优表型（local environmental optimum）之间的关联关系。本研究通过在有无致死性寄生虫的环境中，对关键宿主性状的平均值与方差进行析因操控，证实增加表型方差可对宿主种群产生有益影响（例如削弱疾病流行规模），但这一效应仅在种群初始表型与局部环境适配性较差时才会显现。与之相反，当初始表型已适配环境条件时，更高的表型方差...