Data from: Ecological explanations to island gigantism: dietary niche divergence, predation and size in an endemic lizard

Although rapid evolution of body size on islands has long been known, the ecological mechanisms behind this island phenomenon remain poorly understood. Diet is an important selective pressure for morphological divergence. Here we investigate if selection for novel diets has contributed to the multiple independent cases of island gigantism in the Skyros wall lizard (Podarcis gaigeae) and if diet, predation, or both factors best explain island gigantism. We combined data on body size, shape, bite force, and realized and available diets to address this. Several lines of evidence suggest that diet has contributed to the island gigantism. The larger islet lizards have relatively wider heads and higher bite performance in relation to mainland lizards than would be expected from size differences alone. The proportions of consumed and available hard prey are higher on islets than mainland localities, and lizard body size is significantly correlated with the proportion of hard prey. Furthermore, the main axis of divergence in head shape is significantly correlated with dietary divergence. Finally, a model with only diet and one including diet and predation regime explain body size divergence equally well. Our results suggest that diet is an important ecological factor behind insular body size divergence, but could be consistent with an additional role for predation.

尽管岛屿上的体型快速演化现象早已为学界熟知，但这一岛屿特有现象背后的生态机制仍未得到充分阐释。食物资源是驱动形态分化的重要选择压力来源。本研究以西克罗壁蜥（Podarcis gaigeae）为研究对象，旨在探究针对新型食物的选择是否促成了其种群中多起独立演化的岛屿巨型化事件，同时明确食物资源、捕食压力，或是二者共同作用能否最佳解释岛屿巨型化现象。我们整合了体型、形态、咬合力，以及实际摄食食谱与可获取食物资源的相关数据来解答上述问题。多维度证据均表明食物资源参与了岛屿巨型化的演化过程：相较于仅由体型差异所预期的水平，岛屿种群的壁蜥头部相对更宽，咬合力也显著强于大陆种群；岛屿生境中，壁蜥实际摄食与可获取的硬质猎物占比均高于大陆分布区，且壁蜥体型与硬质猎物占比呈显著正相关；此外，头部形态分化的核心主轴与食谱分化显著相关。最后，仅纳入食物资源的模型，与同时纳入食物资源与捕食模式的模型，对体型分化的解释力不相伯仲。本研究结果表明，食物资源是导致岛屿种群体型分化的重要生态因子，同时也不排除捕食压力发挥额外作用的可能性。