Table S2 from The influence of wing morphology upon the dispersal, geographical distributions and diversification of the Corvides (Aves; Passeriformes)

New species are sometimes known to arise as a consequence of the dispersal and establishment of populations in new areas. It has nevertheless been difficult to demonstrate an empirical link between rates of dispersal and diversification, partly because dispersal abilities are challenging to quantify. Here, using wing morphology as a proxy for dispersal ability, we assess this relationship among the global radiation of corvoid birds. We found that species distributions are associated with wing shape. Widespread species (occurring on both islands and continents), and those that are migratory, exhibit wing morphologies better adapted to long-distance flight compared with sedentary continental or insular forms. Habitat preferences also strongly predict wing form, with species that occur in canopies and/or areas of sparse vegetation possessing dispersive morphologies. By contrast, we found no significant differences in diversification rates among either the migratory or habitat classifications, but species distributed in island settings diversify at higher rates than those found on continents. This latter finding may reflect the elevated dispersal capabilities of widespread taxa, facilitating the radiation of these lineages across insular areas. However, as the correlations between wing morphology and diversification rates were consistently weak throughout our dataset, this suggests that historical patterns of diversification are not particularly well reflected by present-day wing morphology.

学界已知，新物种有时会因种群在新区域的扩散与定殖而形成。然而，要实证阐明扩散速率与物种分化速率之间的关联始终颇具挑战，部分原因在于扩散能力难以量化。本研究以翼形作为扩散能力的替代指标，针对鸦总科鸟类（Corvoid birds）的全球辐射演化类群，检验二者之间的关联。研究结果显示，物种分布范围与翼形存在显著关联：广泛分布（同时栖息于岛屿与大陆）的物种以及迁徙性物种，其翼形更适配长距离飞行，相较之下，大陆留居或岛屿留居的类群则不具备这类特征。栖息地偏好同样可显著预测翼形特征，栖息于林冠层或稀疏植被区域的物种，多具备利于扩散的翼形。相较而言，本研究未发现迁徙类群或不同栖息地类群间的物种分化速率存在显著差异，但分布于岛屿的类群，其分化速率显著高于大陆类群。这一结果或许反映了广布类群较强的扩散能力，助力这些演化支系在岛屿区域实现辐射演化。不过，由于本数据集内翼形与分化速率之间的相关性始终较弱，这表明现生翼形特征并不能很好地反映物种的历史分化模式。