Bite force is a key performance trait in lizards because biting is involved in many ecologically relevant tasks, including foraging, fighting and mating. Several factors have been suggested to impact bite force in lizards, such as head morphology (proximate factors), or diet, intraspecific competition and habitat characteristics (ultimate factors). However, these have been generally investigated separately and mostly at the interspecific level. Here we tested which factors drive variation in bite force at the population level and to what extent. Our study includes 20 populations of two closely related lacertid species, Podarcis melisellensis and Podarcis sicula, which inhabit islands in the Adriatic. We found that lizards with more forceful bites have relatively wider and taller heads, and consume more hard prey and plant material. Island isolation correlates with bite force, probably by driving resource availability. Bite force is only poorly explained by proxies of intraspecific competition. The linear distance from a large island and the proportion of difficult-to-reduce food items consumed are the ultimate factors that explain most of the variation in bite force. Our findings suggest that the way in which morphological variation affects bite force is species-specific, probably reflecting the different selective pressures operating on the two species.

中文翻译：

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岛屿蜥蜴Podarcis melisellensis和Podarcis sicula咬合力变化的最接近和最终驱动力

咬力是蜥蜴的一项重要性能特征，因为咬伤涉及许多与生态相关的任务，包括觅食，战斗和交配。已经提出了影响蜥蜴咬咬力的几个因素，例如头部形态（附近因素）或饮食，种内竞争和栖息地特征（最终因素）。但是，这些已被单独研究，并且大多在种间水平上进行了研究。在这里，我们测试了哪些因素会导致人口水平上的咬合力变化以及影响程度。我们的研究包括20个紧密相关的Lacertid物种（Podarcis melisellensis和Podarcis sicula）的种群，栖息在亚得里亚海的岛屿上。我们发现，叮咬力更强的蜥蜴的头部相对更宽且更高，并且会消耗更多的坚硬猎物和植物材料。孤岛隔离可能与咬合力相关，这可能是通过驱动资源的可用性来实现的。咬合力只能通过种内竞争的代理来解释。到大岛的直线距离以及所消耗的难以减少的食品所占的比例是解释大多数咬力变化的最终因素。我们的发现表明，形态变异影响咬合力的方式是特定于物种的，可能反映了对这两个物种起作用的不同选择压力。