Navalón Guillermo, Nebreda Sergio M, Bright Jen A, Fabbri Matteo, Benson Roger B J, Bhullar Bhart-Anjan, Marugán-Lobón Jesús, Rayfield Emily J
Department of Earth Sciences, University of Oxford, Oxford, UK.
Unidad de Paleontología, Departamento de Biología, Universidad Autónoma de Madrid, Madrid, Spain.
Proc Biol Sci. 2021 Apr 14;288(1948):20210181. doi: 10.1098/rspb.2021.0181.
Evolutionary variation in ontogeny played a central role in the origin of the avian skull. However, its influence in subsequent bird evolution is largely unexplored. We assess the links between ontogenetic and evolutionary variation of skull morphology in Strisores (nightbirds). Nightbirds span an exceptional range of ecologies, sizes, life-history traits and craniofacial morphologies constituting an ideal test for evo-devo hypotheses of avian craniofacial evolution. These morphologies include superficially 'juvenile-like' broad, flat skulls with short rostra and large orbits in swifts, nightjars and allied lineages, and the elongate, narrow rostra and globular skulls of hummingbirds. Here, we show that nightbird skulls undergo large ontogenetic shape changes that differ strongly from widespread avian patterns. While the superficially juvenile-like skull morphology of many adult nightbirds results from convergent evolution, rather than paedomorphosis, the divergent cranial morphology of hummingbirds originates from an evolutionary reversal to a more typical avian ontogenetic trajectory combined with accelerated ontogenetic shape change. Our findings underscore the evolutionary lability of cranial growth and development in birds, and the underappreciated role of this aspect of phenotypic variability in the macroevolutionary diversification of the amniote skull.
个体发育中的进化变异在鸟类头骨的起源中起着核心作用。然而，其在后续鸟类进化中的影响在很大程度上尚未得到探索。我们评估了夜鸟（夜禽）头骨形态的个体发育变异与进化变异之间的联系。夜鸟涵盖了异常广泛的生态、体型、生活史特征和颅面形态，构成了对鸟类颅面进化的演化发育生物学假设的理想测试。这些形态包括在雨燕、夜鹰及相关谱系中表面上类似“幼体”的宽阔、扁平头骨，其喙短且眼眶大，以及蜂鸟细长、狭窄的喙和球状头骨。在这里，我们表明夜鸟头骨在个体发育过程中会发生巨大的形态变化，这与广泛存在的鸟类模式有很大不同。虽然许多成年夜鸟表面上类似幼体的头骨形态是趋同进化的结果，而非幼态持续，但蜂鸟不同的颅骨形态源于向更典型的鸟类个体发育轨迹的进化逆转，再加上加速的个体发育形态变化。我们的研究结果强调了鸟类颅骨生长和发育的进化可塑性，以及这种表型变异性在羊膜动物头骨宏观进化多样化中未得到充分重视的作用。
