Chiroptera is the only group of mammals capable of powered flight. The mechanical basis of bat flight is well established, but evolution of its constituent aerodynamic variables remains poorly understood. Here, we determine the macroevolutionary patterns of traditional aerodynamic variables (wing loading, aspect ratio, tip shape index) in a comprehensive phylogeny of Chiroptera using an extensive dataset including key Eocene fossils. We optimized variables as continuous characters and fit models of character evolution to identify shifts in character optima. The reconstructed ancestral chiropteran morphotype presented low wing loading and low-to-intermediate aspect ratio, and remained unaltered for much of the first half of bat evolution (Paleogene). This evolutionary pattern may be explained by stabilizing selection responding to the strong constraints imposed by echolocation and flight on body size, and the physical constraints regarding aerodynamic efficiency acting on wing shape. Posterior specialization in some groups permitted divergence toward novel aerodynamic morphotypes in the second half of chiropteran evolutionary history (Neogene). We linked the most notable aerodynamic changes to ecological release from echolocation constraints (Pteropodidae), dietary-foraging shifts (Phyllostomidae, Noctilionidae), or advantage in face of environmental changes (Molossidae, Taphozoinae). The independently-evolved specialization of fast, enduring flight that allowed Molossidae and Taphozoinae (Emballonuridae) to perform aerial hawking of swarming insects in open spaces was linked to significant shifts in the optima of both wing loading and aspect ratio. These shifts were probably associated with the gradual spread of open-mosaic landscapes at a global scale since the Oligocene.

中文翻译：

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蝙蝠（哺乳动物：手足目）传统空气动力学变量在综合系统发育框架内的演变

手足目是唯一能够进行动力飞行的哺乳动物。蝙蝠飞行的机械基础已经确立，但其组成空气动力学变量的演变仍知之甚少。在这里，我们使用包括关键始新世化石在内的广泛数据集确定了手足目综合系统发育中传统空气动力学变量（翼载荷、纵横比、尖端形状指数）的宏观进化模式。我们将变量优化为连续字符并拟合字符进化模型，以识别字符优化的变化。重建的祖先手足目形态型呈现出低翼载荷和中低纵横比，并且在蝙蝠进化的前半部分（古近纪）的大部分时间里保持不变。这种进化模式可以通过稳定选择来解释，以响应回声定位和飞行对体型的强约束，以及关于空气动力学效率的物理约束作用于机翼形状。某些群体的后向专业化允许在手足类进化史的后半部分（新近纪）向新的空气动力学形态类型分化。我们将最显着的空气动力学变化与回声定位约束（翼足科）、饮食觅食变化（叶螈科、夜蛾科）或面对环境变化的优势（蚊科、螟蛉科）的生态释放联系起来。自主发展的快速专业化，允许 Molossidae 和 Taphozoinae（Emballonuridae）在开放空间中对成群昆虫进行空中兜售的持久飞行与翼载荷和纵横比的优化显着变化有关。这些变化可能与渐新世以来开放镶嵌景观在全球范围内的逐渐扩散有关。