Repeated evolution of terrestrial lineages in a continental lizard radiation

The ‘early-burst’ model of adaptive radiation predicts an early increase in phenotypic disparity concurrent with lineage diversification. Although most studies report a lack of this coupled pattern, the underlying processes are not identified. The continental radiation of <i>Hemidactylus</i> geckos from Peninsular India includes morphologically diverse species that occupy various microhabitats. This radiation began diversifying ~36 Mya with an early increase in lineage diversification. Here, we test the ‘early-burst’ hypothesis by investigating the presence of ecomorphs and examining the pattern of morphological diversification in a phylogenetic framework. Two ecomorphs— terrestrial and scansorial species— that vary significantly in body size and toepad size were identified. Unlike the prediction of the ‘early-burst’ model, we find that disparity in toepad morphology accumulated more recently ~14 Mya and fit the OU model. Ancestral state reconstruction of the two ecomorphs d...适应辐射的早期爆发（early-burst）模型预测，表型差异会与谱系分化在早期同步增长。尽管多数研究未观测到该耦合模式，但其背后的潜在机制仍未明确。来自印度半岛的趾虎属（Hemidactylus）壁虎的大陆辐射演化类群，包含形态多样、栖息于各类微生境的物种。该辐射演化始于约36百万年前（Mya），早期经历了谱系分化的快速增长。本研究通过调查生态形态型（ecomorph）的存在情况，并在系统发育框架下分析形态分化模式，对早期爆发假说进行检验。研究共识别出两类生态形态型：陆生与攀援型物种，二者在体型与趾垫尺寸上均存在显著差异。与早期爆发模型的预测相悖，我们发现趾垫形态的差异积累发生在更晚的约14百万年前，且符合奥恩斯坦-乌伦贝克（OU）模型。对两类生态形态型的祖先状态重建……