Department of Earth Sciences, University of Cambridge, Cambridge, UK.
Department of Earth Sciences, University of Oxford, Oxford, UK.
Nature. 2022 Nov;611(7935):306-311. doi: 10.1038/s41586-022-05372-y. Epub 2022 Oct 26.
Characterizing how variation in the tempo and mode of evolution has structured the phenotypic diversity of extant species is a central goal of macroevolution. However, studies are typically limited to a handful of traits, providing incomplete information. We analyse morphological diversification in living birds, an ecologically diverse group, documenting structural scales from 'pan-skeletal' proportions down to the localized three-dimensional shape changes of individual bones. We find substantial variation in evolutionary modes among avian subgroups and among skeletal parts, indicating widespread mosaicism and possible differences in the structure of the macroevolutionary landscape across Earth's main environments. Water-linked groups, especially Aequorlitornithes (waterbirds), have repeatedly explored a large portion of their total morphospace, emphasizing variation in body proportions and in the shape of bones close to the body core, which are functionally related to the mechanics of locomotion. By contrast, landbirds (Inopinaves) evolved distinct, group-specific body forms early in the aftermath of the K-Pg and subsequently emphasized local shape variation, especially in the head and distal limb bones, which interact more directly with the environment. Passerines, which comprise more than half of all bird species, show a conservative evolutionary dynamic that resulted in low disparity across all skeletal parts. Evidence for early establishment of the morphospace of living birds is clear for some skeletal parts, including beaks and the combined skeletal morphology. However, we find little evidence for early partitioning of that morphospace, contrary to more specific predictions of 'niche-filling' models. Nevertheless, early divergence among broad environmental types may have caused an early divergence of evolutionary modes, suggesting an important role for environmental divergence in structuring the radiation of crown-group birds.
描述进化节奏和模式的变化如何构建现存物种表型多样性是宏观进化的一个核心目标。然而，研究通常仅限于少数几个特征，提供的信息不完整。我们分析了现存鸟类的形态多样性，这是一个生态多样化的群体，记录了从“泛骨骼”比例到个别骨骼的局部三维形状变化的结构尺度。我们发现鸟类亚群之间以及骨骼部位之间的进化模式存在很大差异，这表明在地球的主要环境中，广泛存在镶嵌现象和宏观进化景观结构的可能差异。与水有关的群体，特别是 Aequorlitornithes（水鸟），反复探索了其总形态空间的很大一部分，强调了身体比例的变化和靠近身体核心的骨骼形状的变化，这些变化与运动力学有关。相比之下，陆鸟（Inopinaves）在 K-Pg 之后的早期就进化出了独特的、特定于群体的体型，随后强调了局部形状的变化，特别是在头部和远端肢体骨骼上，这些骨骼与环境的相互作用更为直接。鸣禽，占所有鸟类物种的一半以上，表现出保守的进化动态，导致所有骨骼部位的差异都很低。一些骨骼部位，包括喙和组合骨骼形态，都有明确的证据表明现存鸟类形态空间的早期建立。然而，我们几乎没有发现该形态空间早期分区的证据，这与“填补生态位”模型的更具体预测相反。尽管如此，广泛环境类型的早期分化可能导致了进化模式的早期分化，这表明环境分化在构建冠群鸟类的辐射中起着重要作用。
