Institute of Evolutionary Biology, University of Edinburgh, Edinburgh, UK.
J Evol Biol. 2018 Aug;31(8):1109-1126. doi: 10.1111/jeb.13290. Epub 2018 Jun 11.
Phenotypic polymorphism in cryptic species is widespread. This may evolve in response to search image use by predators exerting negative frequency-dependent selection on intraspecific colour morphs, 'apostatic selection'. Evidence exists to indicate search image formation by predators and apostatic selection operating on wild prey populations, though not to demonstrate search image use directly resulting in apostatic selection. The present study attempted to address this deficiency, using British Lepidoptera active in winter as a model system. It has been proposed that the typically polymorphic wing colouration of these species represents an anti-search image adaptation against birds. To test (a) for search image-driven apostatic selection, dimorphic populations of artificial moth-like models were established in woodland at varying relative morph frequencies and exposed to predation by natural populations of birds. In addition, to test (b) whether abundance and degree of polymorphism are correlated across British winter-active moths, as predicted where search image use drives apostatic selection, a series of phylogenetic comparative analyses were conducted. There was a positive relationship between artificial morph frequency and probability of predation, consistent with birds utilizing search images and exerting apostatic selection. Abundance and degree of polymorphism were found to be positively correlated across British Lepidoptera active in winter, though not across all taxonomic groups analysed. This evidence is consistent with polymorphism in this group having evolved in response to search image-driven apostatic selection and supports the viability of this mechanism as a means by which phenotypic and genetic variation may be maintained in natural populations.
表型多态性在隐种中很常见。这可能是由于捕食者对同种颜色形态的负频率依赖选择（“逆选择”）而导致的搜索图像使用进化而来的。有证据表明捕食者形成了搜索图像，并对野生猎物种群进行了逆选择，但没有直接证明搜索图像的使用导致了逆选择。本研究试图通过以英国冬季活动的鳞翅目昆虫为模型系统来解决这一不足。有人提出，这些物种典型的多态翅膀颜色代表了一种针对鸟类的反搜索图像适应。为了检验（a）搜索图像驱动的逆选择，在不同的相对形态频率下，在林地中建立了人工蛾状模型的二态种群，并使其暴露于鸟类的自然种群捕食下。此外，为了检验（b）是否如搜索图像使用驱动逆选择所预测的那样，在英国冬季活动的飞蛾中，丰度和多态性程度之间存在相关性，进行了一系列系统发育比较分析。人工形态频率与捕食概率之间呈正相关，这与鸟类利用搜索图像并施加逆选择一致。在英国冬季活动的鳞翅目昆虫中，丰度和多态性程度之间存在正相关，但在分析的所有分类群中并非如此。这一证据表明，该群体的多态性是由于搜索图像驱动的逆选择而进化而来的，并支持了这种机制的可行性，即作为一种维持自然种群中表型和遗传变异的手段。
