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.

尽管岛屿类群体型快速演化的现象早已为人熟知，但这一岛屿特有现象背后的生态机制仍未得到充分阐释。饮食是驱动形态分化的关键选择压力来源。本研究以斯基罗斯壁蜥（Podarcis gaigeae）为研究对象，旨在探究针对新型饮食的选择是否推动了该物种多起独立的岛屿巨型化事件，同时验证饮食、捕食压力或二者共同作用是否能最佳解释岛屿巨型化现象。为此，我们整合了体型、头部形态、咬合力，以及实际摄食食谱与可利用猎物资源的相关数据开展研究。多项证据表明，饮食因素确实推动了岛屿巨型化的发生：相较于大陆种群，小岛蜥蜴的头部相对更宽，且咬合力表现超出仅由体型差异所能解释的水平；小岛生境中，被摄食与可获取的硬质猎物占比均高于大陆分布区，且蜥蜴体型与硬质猎物占比呈显著正相关；此外，头部形态分化的主要主轴与食谱分化呈显著相关。最终，仅纳入饮食因素的模型，与同时包含饮食及捕食压力的模型，对体型分化的解释效果相当。本研究结果显示，饮食是驱动岛屿类群体型分化的重要生态因子，但同时也不排除捕食压力可能存在的附加作用。