Monday, October 27, 2014

[BioGeography / Herpetology • 2014] Crossing the Line: Increasing Body Size in a trans-Wallacean Lizard Radiation (Cyrtodactylus, Gekkota)

Figure 1. Dated phylogeny (Bayesian MCC tree) for Cyrtodactylus estimated with concatenated nuclear and mitochondrial dataset showing divergence dates and ancestral state reconstructions for body length (blue smallest, green intermediate and red largest); taxon names and posterior probabilities are given in the electronic supplementary material, figure S1; exact ages and sizes of all nodes (with 95% highest posterior density (HPD) intervals) are in electronic supplementary material, file SI_4. Yellow shading denotes the two clades occurring in the Australopapuan region. Grey bars at right denote maximum body size for each species (in mm), with grey shading denoting larger-bodied clades in Asian and Australopapuan regions.

The region between the Asian and Australian continental plates (Wallacea) demarcates the transition between two differentiated regional biotas. Despite this striking pattern, some terrestrial lineages have successfully traversed the marine barriers of Wallacea and subsequently diversified in newly colonized regions. The hypothesis that these dispersals between biogeographic realms are correlated with detectable shifts in evolutionary trajectory has however rarely been tested. Here, we analyse the evolution of body size in a widespread and exceptionally diverse group of gekkotan lizards (Cyrtodactylus), and show that a clade that has dispersed eastwards and radiated in the Australopapuan region appears to have significantly expanded its body size ‘envelope’ and repeatedly evolved gigantism. This pattern suggests that the biotic composition of the proto-Papuan Archipelago provided a permissive environment in which new colonists were released from evolutionary constraints operating to the west of Wallacea.

Keywords: Asia; Cyrtodactylus; ecological release; insular gigantism; New Guinea; Wallace's Line

Paul M. Oliver, Phillip Skipwith and Michael S. Y. Lee. 2014. Crossing the Line: Increasing Body Size in a trans-Wallacean Lizard Radiation (Cyrtodactylus, Gekkota). Biology Letters. DOI: 10.1098/rsbl.2014.0479

Geckos crossed the line and got bigger

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