Baken Erica K, Adams Dean C
Department of Ecology, Evolution, and Organismal Biology Iowa State University Ames Iowa.
Ecol Evol. 2019 May 26;9(12):7005-7016. doi: 10.1002/ece3.5267. eCollection 2019 Jun.
Evolutionary theory predicts that selection in distinct microhabitats generates correlations between morphological and ecological traits, and may increase both phenotypic and taxonomic diversity. However, some microhabitats exert unique selective pressures that act as a restraining force on macroevolutionary patterns of diversification. In this study, we use phylogenetic comparative methods to investigate the evolutionary outcomes of inhabiting the arboreal microhabitat in salamanders. We find that arboreality has independently evolved at least five times in Caudata and has arisen primarily from terrestrial ancestors. However, the rate of transition from arboreality back to terrestriality is 24 times higher than the converse. This suggests that macroevolutionary trends in microhabitat use tend toward terrestriality over arboreality, which influences the extent to which use of the arboreal microhabitat proliferates. Morphologically, we find no evidence for an arboreal phenotype in overall body proportions or in foot shape, as variation in both traits overlaps broadly with species that utilize different microhabitats. However, both body shape and foot shape display reduced rates of phenotypic evolution in arboreal taxa, and evidence of morphological convergence among arboreal lineages is observed. Taken together, these patterns suggest that arboreality has played a unique role in the evolution of this family, providing neither an evolutionary opportunity, nor an evolutionary dead end.
进化理论预测，在不同的微生境中进行选择会导致形态特征与生态特征之间产生关联，并可能增加表型多样性和分类多样性。然而，一些微生境会施加独特的选择压力，对多样化的宏观进化模式起到限制作用。在本研究中，我们使用系统发育比较方法来探究蝾螈栖息于树栖微生境的进化结果。我们发现，树栖习性在有尾目动物中至少独立进化了五次，且主要起源于陆生祖先。然而，从树栖习性转变回陆生习性的速率比相反转变的速率高24倍。这表明在微生境利用方面的宏观进化趋势倾向于陆生而非树栖，这影响了树栖微生境利用的扩散程度。在形态上，我们没有发现整体身体比例或足部形状存在树栖表型的证据，因为这两个特征的变异与利用不同微生境的物种广泛重叠。然而，树栖类群的身体形状和足部形状的表型进化速率均有所降低，并且观察到树栖谱系之间存在形态趋同的证据。综上所述，这些模式表明树栖习性在该科的进化中发挥了独特作用，既没有提供进化机会，也不是进化的死胡同。
