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...