Data from: Predator perspective drives geographic variation in frequency-dependent polymorphism

Color polymorphism in natural populations can manifest as a striking patchwork of phenotypes in space, with neighboring populations characterized by dramatic differences in morph composition. These "geographic mosaics" can be challenging to explain in the absence of localized selection because they are unlikely to result from simple isolation-by-distance or clinal variation in selective regimes. To identify processes that can lead to the formation of geographic mosaics, we developed a simulation-based model to explore the influence of predator perspective, selection, migration, and genetic linkage of color loci on allele frequencies in polymorphic populations in space and time. Using simulated populations inspired by the biology of Heliconius longwing butterflies, Cepaea land snails, Oophaga poison frogs, and Sonora ground snakes, we found that the relative sizes of predator and prey home ranges can produce large differences in morph composition between neighboring populations under both positive and negative frequency-dependent selection. We also demonstrate the importance of the interaction of predator perspective with the type of frequency-dependence and localized directional selection across migration and selection intensities. Our results demonstrate that regional-scale predation can promote the formation of phenotypic mosaics in prey species, without the need to invoke spatial variation in selective regimes. We suggest that predator behavior can play an important and underappreciated role in the formation and maintenance of geographic mosaics in polymorphic species.

自然种群中的色彩多态性（color polymorphism）可在空间维度上呈现为醒目的表型镶嵌分布，相邻种群的形态构成往往存在显著差异。这类“地理镶嵌格局（geographic mosaics）”若缺乏局域选择的作用则难以解释，因为它们不太可能由简单的距离隔离（isolation-by-distance）或选择机制的渐变变异（clinal variation）所导致。为厘清可驱动地理镶嵌格局形成的潜在过程，我们开发了基于模拟的模型（simulation-based model），以探究捕食者感知（predator perspective）、选择作用、迁移以及色彩位点的遗传连锁（genetic linkage）对多态种群时空尺度下等位基因频率（allele frequencies）的影响。我们参照釉蛱蝶（Heliconius longwing butterflies）、布纹蜗牛属（Cepaea）陆生蜗牛、箭毒蛙（Oophaga）属物种以及索诺拉地蛇（Sonora ground snakes）的生物学特征构建模拟种群，结果发现，无论在正频率依赖选择（positive frequency-dependent selection）还是负频率依赖选择（negative frequency-dependent selection）情境下，捕食者与猎物活动家域（home ranges）的相对大小，均可导致相邻种群间的形态构成产生显著差异。我们还证实，捕食者感知与频率依赖（frequency-dependence）选择类型、局域定向选择（localized directional selection）之间的交互作用，在不同迁移强度与选择强度条件下均发挥关键作用。本研究结果表明，区域尺度捕食作用（regional-scale predation）可推动猎物种群形成表型镶嵌格局，而无需借助选择机制空间变异这一前提。我们认为，捕食者行为在多态物种地理镶嵌格局的形成与维持中，可发挥重要且长期被低估的作用。