Human activity drastically transforms landscapes, generating novel habitats to which species must adaptively respond. Consequently, urbanization is increasingly recognized as a driver of phenotypic change. The structural environment of urban habitats presents a replicated natural experiment to examine trait–environment relationships and phenotypic variation related to locomotion. We use geometric morphometrics to examine claw morphology of five species of Anolis lizards in urban and forest habitats. We find that urban lizards undergo a shift in claw shape in the same direction but varying magnitude across species. Urban claws are overall taller, less curved, less pointed and shorter in length than those of forest lizards. These differences may enable more effective attachment or reduce interference with toepad function on smooth anthropogenic substrates. We also find an increase in shape disparity, a measurement of variation, in urban populations, suggesting relaxed selection or niche expansion rather than directional selection. This study expands our understanding of the relatively understudied trait of claw morphology and adds to a growing number of studies demonstrating phenotypic changes in urban lizards. The consistency in the direction of the shape changes we observed supports the intriguing possibility that urban environments may lead to predictable convergent adaptive change.

中文翻译：

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城市适应的优点：蜥蜴爪形态的种内变异

人类的活动极大地改变了景观，产生了新的生境，物种必须对此做出适应性的反应。因此，人们日益认识到城市化是表型变化的驱动力。城市栖息地的结构环境提出了一个重复的自然实验，以检验与运动有关的性状-环境关系和表型变异。我们使用几何形态计量学检查五种Anolis的爪形城市和森林栖息地的蜥蜴。我们发现，城市蜥蜴的爪形向同一方向变化，但跨物种的大小却有所不同。与森林蜥蜴相比，城市爪总体上更高，弯曲更少，尖端更短且长度更短。这些差异可以实现更有效的附着，或减少对光滑人为基材上脚趾板功能的干扰。我们还发现，城市人口中的形状差异（一种变化的度量）在增加，这表明选择放松或利基扩张而不是方向选择。这项研究扩大了我们对爪子形态相对未被研究的特征的理解，并增加了越来越多的研究表明城市蜥蜴的表型发生了变化。