Data from: Contrasting trajectories of morphological diversification on continents and islands in the Afrotropical white-eye radiation

Aim Morphological and lineage evolution are predicted to follow different patterns in island and mainland radiations. However, the extent to which these geographical contexts influence evolutionary trajectories remains poorly understood, in part because few studies have focused on species-rich clades colonising continents and archipelagos over comparable timeframes. Focusing on a diverse songbird clade radiating on the African continent and adjacent islands, we tested whether morphological evolution is best explained by adaptive or non-adaptive processes, and whether mainland and island lineages evolved to occupy different regions or volumes of morphological space (morphospace). Location Palaeotropics, with a particular focus on the Afrotropical region. Taxon White-eyes, Zosterops (Aves: Zosteropidae) Methods We generated principal component axes from novel trait data for 120 species and combined this information with a comprehensive dated phylogeny. We then analysed the dynamics of trait and lineage diversification using comparative evolutionary methods. Results An early burst and slowdown pattern of lineage accumulation is not mirrored by phenotypic evolution, which instead shows an apparent convergence on particular phenotypes. However, the overall signature of phenotypic convergence is strongly driven by mainland taxa, in which phenotypes appear to be highly constrained within elevational zones, while speciation events are often associated with phenotypic divergence from one body plan to the other after colonisation of highland from lowland habitats, or vice versa. By contrast, island lineages have repeatedly explored novel areas of morphospace with patterns of phenotypic divergence generally not distinguishable from a random-walk model. Main conclusions Diversification of Zosterops highlights contrasting evolutionary trends and dynamics for continental versus island species. We suggest the different trajectory of evolution in insular lineages arises from reduced species competition leading to an increase in ecological opportunity, thereby providing a release to phenotypic constraints experienced by continental taxa.

研究目标：形态演化与谱系演化在岛屿辐射类群与大陆辐射类群中被预测呈现不同模式。然而，此类地理背景对演化轨迹的影响程度仍不甚明晰，部分原因在于鲜有研究聚焦于在可比时间尺度内分别拓殖大陆与群岛的物种丰富支系。
本研究以在非洲大陆及邻近岛屿辐射演化的多样鸣禽支系为研究对象，检验形态演化究竟更符合适应性过程还是非适应性过程的解释，同时探究大陆与岛屿谱系是否演化出占据不同区域或体积的形态空间（morphospace）。
研究区域：古热带区，尤其聚焦于非洲热带区。
研究类群：绣眼鸟属（Zosterops）鸟类（鸟纲：绣眼鸟科Zosteropidae）。
研究方法：我们基于120个物种的全新性状数据生成主成分轴，并将该信息与一套完整的时间校准系统发育树相结合；随后采用比较演化分析法解析性状与谱系分化的动态过程。
研究结果：谱系积累的早期爆发与减缓模式并未在表型演化中得到体现，后者反而呈现出向特定表型的显著趋同特征。然而，表型趋同的整体信号主要由大陆类群驱动：大陆类群的表型似乎严格受海拔带限制，而物种形成事件往往伴随从低海拔栖息地拓殖高海拔栖息地（或反之）后，从一种身体构型向另一种构型的表型分化。与之形成对比的是，岛屿谱系反复拓展了形态空间的全新区域，其表型分化模式通常无法与随机游走模型区分开来。
主要结论：绣眼鸟属（Zosterops）的分化过程揭示了大陆与岛屿物种间截然不同的演化趋势与动态。我们认为，岛屿谱系演化轨迹的差异源于物种竞争减弱带来的生态机会增加，从而解除了大陆类群所受到的表型约束。