Ecological specialization and morphological diversification in Greater Antillean boas

Colonization of islands can dramatically influence the evolutionary trajectories of organisms, with both deterministic and stochastic processes driving adaptation and diversification. Some island colonists evolve extremely large or small body sizes, presumably in response to unique ecological circumstances present on islands. One example of this phenomenon, the Greater Antillean boas, includes both small (<90 cm) and large (4 m) species occurring on the Greater Antilles and Bahamas, with some islands supporting pairs or trios of body-size divergent species. These boas have been shown to comprise a monophyletic radiation arising from a Miocene dispersal event to the Greater Antilles, though it is not known whether co-occurrence of small and large species is a result of dispersal or in situ evolution. Here, we provide the first comprehensive species phylogeny for this clade combined with morphometric and ecological data to show that small body size evolved repeatedly on separate island...

岛屿定殖可显著影响生物的演化轨迹，确定性与随机过程共同驱动适应性演化与物种分化。部分岛屿定居类群会演化出极端偏大或偏小的体型，推测这是对岛屿独特生态环境的适应响应。大安的列斯群岛蚺（Greater Antillean boas）便是该现象的典型类群：其在大安的列斯群岛与巴哈马群岛分布有体型小于90厘米的小型物种与长达4米的大型物种，部分岛屿还共存有体型差异显著的物种对或物种组。已有研究证实，该类群属于单系辐射演化类群（monophyletic radiation），起源于中新世（Miocene）一次扩散至大安的列斯群岛的事件，但目前仍无法明确小型与大型物种的同域共存究竟源于多次跨岛扩散，还是原位演化。本研究首次构建了该演化支的全面物种系统发育树，并结合形态测量学（morphometric）与生态数据，证实小型体型在不同独立岛屿上多次独立演化