Reynolds R Graham, Collar David C, Pasachnik Stesha A, Niemiller Matthew L, Puente-Rolón Alberto R, Revell Liam J
Department of Organismic and Evolutionary Biology and Museum of Comparative Zoology, Harvard University, Cambridge, Massachusetts, 02138.
Current Address: University of North Carolina Asheville, Department of Biology, One University Heights, Asheville, North Carolina, 28804.
Evolution. 2016 Aug;70(8):1882-95. doi: 10.1111/evo.12987. Epub 2016 Jul 27.
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 islands in association with specialization in substrate use. Our results further suggest that microhabitat specialization is linked to increased rates of head shape diversification among specialists. Our findings show that ecological specialization following island colonization promotes morphological diversity through deterministic body size evolution and cranial morphological diversification that is contingent on island- and species-specific factors.
岛屿的殖民化会极大地影响生物的进化轨迹，确定性和随机性过程都会推动生物的适应和多样化。一些岛屿殖民者会进化出极大或极小的体型，这大概是对岛屿上独特生态环境的一种响应。这种现象的一个例子是大安的列斯群岛的蟒蛇，包括分布在大安的列斯群岛和巴哈马群岛的小型（<90厘米）和大型（4米）物种，有些岛屿上同时存在体型差异较大的成对或三个物种。这些蟒蛇已被证明是一个单系辐射类群，起源于中新世向大安的列斯群岛的扩散事件，不过小型和大型物种的共存是扩散的结果还是就地进化的结果尚不清楚。在这里，我们首次为这个类群提供了全面的物种系统发育，并结合形态测量和生态数据表明，小型体型在不同岛屿上反复进化，与底物利用的特化有关。我们的结果进一步表明，微生境特化与特化物种头部形状多样化的增加率有关。我们的研究结果表明，岛屿殖民化后的生态特化通过确定性的体型进化和取决于岛屿及物种特定因素的颅骨形态多样化促进了形态多样性。
