Data from: Local adaptation when competition depends on phenotypic similarity

Recent work incorporating demographic–genetic interactions indicates the importance of population size, gene flow, and selection in influencing local adaptation. This work typically assumes that density-dependent survival affects individuals equally, but individuals in natural population rarely compete equally. Among-individual differences in resource use generate stronger competition between more similar phenotypes (frequency-dependent competition) but it remains unclear how this additional form of selection changes the interactions between population size, gene flow, and local stabilizing selection. Here, we integrate migration–selection dynamics with frequency-dependent competition. We developed a coupled demographic-quantitative genetic model consisting of two patches connected by dispersal and subject to local stabilizing selection and competition. Our model shows that frequency-dependent competition slightly increases local adaptation, greatly increases genetic variance within patches, and reduces the amount that migration depresses population size, despite the increased genetic variance load. The effects of frequency-dependence depend on the strength of divergent selection, trait heritability, and when mortality occurs in the life cycle in relation to migration and reproduction. Essentially, frequency-dependent competition reduces the density-dependent interactions between migrants and residents, the extent to which depends on how different and common immigrants are compared to residents. Our results add new dynamics that illustrate how competition can alter the effects of gene flow and divergent selection on local adaptation and population carrying capacities.近期纳入种群统计-遗传互作（demographic–genetic interactions）的研究表明，种群大小、基因流（gene flow）与选择在本地适应（local adaptation）的调控过程中发挥着关键作用。此类研究通常假定密度依赖型生存（density-dependent survival）对所有个体的影响均等，但自然种群中的个体间竞争实则极少呈现均等状态。个体间在资源利用上的差异会使表型相似的个体间产生更强的竞争，即频率依赖竞争（frequency-dependent competition），但目前仍不清楚这种额外的选择形式会如何改变种群大小、基因流与本地稳定选择（local stabilizing selection）之间的互作关系。本研究将迁移-选择动态（migration–selection dynamics）与频率依赖竞争相结合，构建了一个耦合的种群统计-数量遗传模型（demographic-quantitative genetic model）：该模型包含两个通过扩散相互连接的生境斑块，并受本地稳定选择与竞争作用的影响。模型结果显示，尽管遗传变异负荷（genetic variance load）有所增加，但频率依赖竞争仍能小幅提升本地适应能力，大幅提高生境斑块内的遗传变异水平，并缓解迁移对种群规模的抑制效应。频率依赖效应的强弱取决于分歧选择强度、性状遗传力（trait heritability）以及生命周期中死亡发生的时机相对于迁移与繁殖的先后顺序。本质而言，频率依赖竞争会减弱迁移者与本地个体间的密度依赖互作，其减弱程度取决于外来个体与本地居民的差异程度以及外来个体的相对常见度。本研究结果揭示了全新的动态机制，阐明了竞争如何改变基因流与分歧选择对本地适应及种群承载能力（population carrying capacities）的影响效应。