University of Washington, Seattle, WA, United States.
Oregon Institute of Technology, Klamath Falls, OR, United States.
PeerJ. 2024 Jul 25;12:e17824. doi: 10.7717/peerj.17824. eCollection 2024.
Bats are the only mammals capable of powered flight and have correspondingly specialized body plans, particularly in their limb morphology. The origin of bat flight is still not fully understood due to an uninformative fossil record but, from the perspective of a functional transition, it is widely hypothesized that bats evolved from gliding ancestors. Here, we test predictions of the gliding-to-flying hypothesis of the origin of bat flight by using phylogenetic comparative methods to model the evolution of forelimb and hindlimb traits on a dataset spanning four extinct bats and 231 extant mammals with diverse locomotor modes. Our results reveal that gliders exhibit adaptive trait optima (1) toward relatively elongate forelimbs that are intermediate between those of bats and non-gliding arborealists, and (2) toward relatively narrower but not longer hindlimbs that are intermediate between those of non-gliders and bats. We propose an adaptive landscape based on limb length and width optimal trends derived from our modeling analyses. Our results support a hypothetical evolutionary pathway wherein glider-like postcranial morphology precedes a bat-like morphology adapted to powered-flight, setting a foundation for future developmental, biomechanical, and evolutionary research to test this idea.
蝙蝠是唯一能够进行动力飞行的哺乳动物，相应地具有专门的身体结构，特别是在其肢体形态上。由于化石记录缺乏信息，蝙蝠飞行的起源仍然不完全清楚，但从功能转变的角度来看，广泛假设蝙蝠是从滑翔祖先进化而来的。在这里，我们通过使用系统发育比较方法来检验蝙蝠飞行起源的滑翔假说的预测，该方法对跨越四个已灭绝的蝙蝠和 231 种具有不同运动模式的现存哺乳动物的数据集进行了前肢和后肢特征的进化建模。我们的研究结果表明，滑翔者表现出适应性特征的最优选择（1）相对较长的前肢，介于蝙蝠和非滑翔树栖动物之间，（2）相对较窄但不更长的后肢，介于非滑翔动物和蝙蝠之间。我们基于我们的模型分析得出的肢体长度和宽度最优趋势，提出了一个适应性景观。我们的研究结果支持了一种假设的进化途径，即类似于滑翔的后肢形态先于适应动力飞行的蝙蝠形态，为未来的发育、生物力学和进化研究提供了基础，以检验这一观点。
