Vicars in the desert: Substrate specialisation and paleo-erosion underpin cryptic speciation in an Australian arid-zone lizard lineage (Diplodactylidae: Diplodactylus)

Abstract

Abstract Stable upland habitats in arid zone biomes are often characterised by locally endemic lineages. Explanations for this pattern include habitat or substrate specialisation (ecological specialisation) or intensifying aridity driving retreat into climatically buffered habitats (climatic refugia). Here we present an analysis of these alternative models using genetic, morphological and climate data for Diplodactylus galeatus, a gecko from central Australia that occurs in a series of isolated populations associated with dissected tablelands and mountain ranges. Analyses of mtDNA and SNP data support four distinct lineages, and dating analyses suggest divergence through the Pliocene. Morphological data show slight differences across lineages. Investigation of climate niche shows that two lineages are restricted to areas more arid than the intervening uninhabited region. These data suggest that specialisation to rocky substrates, potentially with subsequent paleo-erosion of dissected tablelands after a Pliocene wet pulse, was the key driver of divergence in this clade. Based on their deep genetic divergence, and differences in morphology and pattern, we recognise two isolated populations as new species.