Trophic divergence despite morphological convergence in a continental radiation of snakes

Ecological and phenotypic convergence is a potential outcome of adaptive radiation in response to ecological opportunity. However, a number of factors may limit convergence during evolutionary radiations, including interregional differences in biogeographic history and clade-specific constraints on form and function. Here, we demonstrate that a single clade of terrestrial snakes from Australia—the oxyuranine elapids—exhibits widespread morphological convergence with a phylogenetically diverse and distantly related assemblage of snakes from North America. Australian elapids have evolved nearly the full spectrum of phenotypic modalities that occurs among North American snakes. Much of the convergence appears to involve the recurrent evolution of stereotyped morphologies associated with foraging mode, locomotion and habitat use. By contrast, analysis of snake diets indicates striking divergence in feeding ecology between these faunas, partially reflecting regional differences in ecological...生态与表型趋同是响应生态机遇（ecological opportunity）的适应辐射（adaptive radiation）的潜在结果。然而，在进化辐射过程中，诸多因素可能限制趋同演化，包括生物地理历史（biogeographic history）的区域差异以及形态与功能的支系特异性约束（clade-specific constraints）。本研究证实，来自澳大利亚的单一支系陆生蛇类——澳蛇亚科（Oxyuraninae Elapidae）类群——与系统发育多样且亲缘关系甚远的北美蛇类类群呈现广泛的形态趋同。澳大利亚眼镜蛇类演化出了近乎覆盖北美蛇类全部表型模态的特征谱系。多数趋同现象似乎涉及与觅食模式（foraging mode）、运动方式（locomotion）及生境利用（habitat use）相关的定型形态的反复演化。相较之下，对蛇类食性的分析显示，这两个动物群的摄食生态（feeding ecology）存在显著分化，这在一定程度上反映了两地生态环境的差异……