Department of Zoology, University of Cambridge, Cambridge, United Kingdom.
Department of Biology, Lund University, Lund, Sweden.
Evolution. 2024 Jul 1;78(7):1302-1316. doi: 10.1093/evolut/qpae059.
Phenotypic plasticity can be adaptive in fluctuating environments by providing rapid environment-phenotype matching and this applies particularly in seasonal environments. African Bicyclus butterflies have repeatedly colonized seasonal savannahs from ancestral forests around the late Miocene, and many species now exhibit seasonal polyphenism. On a macroevolutionary scale, it can be expected that savannah species will exhibit higher plasticity because of experiencing stronger environmental seasonality than forest species. We quantified seasonality using environmental niche modeling and surveyed the degree of plasticity in a key wing pattern element (eyespot size) using museum specimens. We showed that species occurring in highly seasonal environments display strong plasticity, while species in less seasonal or aseasonal environments exhibit surprisingly variable degrees of plasticity, including strong to no plasticity. Furthermore, eyespot size plasticity has a moderate phylogenetic signal and the ancestral Bicyclus likely exhibited some degree of plasticity. We propose hypotheses to explain the range of plasticity patterns seen in less seasonal environments and generate testable predictions for the evolution of plasticity in Bicyclus. Our study provides one of the most compelling cases showing links between seasonality and phenotypic plasticity on a macroevolutionary scale and the potential role of plasticity in facilitating the colonization of novel environments.
表型可塑性可以通过提供快速的环境-表型匹配在波动的环境中具有适应性，这尤其适用于季节性环境。非洲碧凤蝶（Bicyclus）自中新世晚期以来已多次从祖先森林中迁移到季节性稀树草原，现在许多物种表现出季节性多态性。从宏观进化的角度来看，可以预期稀树草原物种由于经历更强的环境季节性，其可塑性会更高。我们使用环境生态位模型量化了季节性，并使用博物馆标本调查了关键翅膀图案元素（眼斑大小）的可塑性程度。我们表明，生活在高度季节性环境中的物种表现出很强的可塑性，而在季节性较弱或无季节性环境中的物种表现出令人惊讶的不同程度的可塑性，包括强可塑性到无可塑性。此外，眼斑大小的可塑性具有中等的系统发育信号，而祖先碧凤蝶可能表现出一定程度的可塑性。我们提出了一些假设来解释在季节性较弱的环境中观察到的可塑性模式的范围，并为碧凤蝶可塑性的进化生成可测试的预测。我们的研究提供了最有说服力的案例之一，表明在宏观进化尺度上季节性和表型可塑性之间存在联系，以及可塑性在促进对新环境的殖民化方面的潜在作用。
