The evolution of fossorial locomotion in the transition from tetrapod to snake-like in lizards

Dramatic evolutionary transitions in morphology are often assumed to be adaptive in a new habitat. However, these assumptions are rarely tested because such tests require intermediate forms, which are often extinct. In vertebrates, the evolution of an elongate, limbless body is generally hypothesized to facilitate locomotion in fossorial and/or cluttered habitats. However, these hypotheses remain untested because few studies examine the locomotion of species ranging in body form from tetrapod to snake-like. Here, we address these functional hypotheses by testing whether trade-offs exist between locomotion in surface, fossorial, and cluttered habitats in Australian Lerista lizards, which include multiple intermediate forms. We found that snake-like species penetrated sand substrates faster than more lizard-like species, representing the first direct support of the adaptation to fossoriality hypothesis. In contrast, body form did not affect surface locomotion or locomotion through clutter...生物形态学上的剧烈演化转变通常被认为是对新栖息环境的适应性演化。然而此类假设极少得到验证——因为相关验证需要依赖中间过渡型物种，而这类物种往往早已灭绝。在脊椎动物类群中，修长无肢躯体的演化通常被推测可提升物种在穴居与（或）复杂杂乱生境中的运动能力。然而此类假说始终未得到验证，原因是鲜有研究针对躯体形态从四足类（tetrapod）向蛇形类渐变的物种开展运动性能分析。本研究以包含多种中间过渡型物种的澳大利亚丽纹石龙子属（Lerista）蜥蜴为研究对象，通过检验其在地表、穴居与复杂生境中的运动性能是否存在权衡关系，以此验证上述功能假说。研究结果显示，蛇形类物种在沙质基质中的穿行速度快于更接近典型蜥蜴形态的物种，这为穴居适应性假说提供了首个直接实验证据。与之相反，躯体形态并未对地表运动或复杂生境中的运动能力产生显著影响……