Die on this hill? A new monotypic, microendemic and montane vertebrate genus from the Australian Wet Tropics

Abstract

The upland rainforests of the Australian Wet Tropics (AWT) are renowned for their diverse and highly relictual biota, and are amongst the best‐studied areas of tropical rainforest in the world. Nonetheless, the evolutionary history of many endemic AWT taxa remains poorly resolved. Here we use molecular data to show that a small thigmothermic and heat‐sensitive lizard endemic to the Thornton Uplands in the northern portion of the AWT is a palaeoendemic that likely diverged from the nearest living taxa around the early Miocene. On the basis of genetic and morphological data, we remove this taxon from the genus Calyptotis where it was formerly placed, redefine Calyptotis and describing a new monotypic genus, Calorodius gen. n. This taxon is the second microendemic, monotypic and montane vertebrate genus recognised from the AWT, and highlights the potential for small areas of upland habitat in AWT to function as evolutionary refugia. However, despite the deep divergence of this lineage, there is no strong evidence that cool‐mesic environments are ancestral to the broader radiation of sphenomorphin skinks that it sits within. The impacts of future anthropogenic climate change on this new genus are difficult to predict, but a tiny range and apparent sensitivity to even relatively moderate temperatures raise concerns, especially if accelerating climate change leads to more regular drought events and heatwaves in the mountain ranges where it occurs.