Analyses of the mitochondrial genome of Leiopelma hochstetteri argues against the full drowning of New Zealand

Abstract

AbstractAimWe used endemic frogs to test the hypothesis that New Zealand was fully submerged during the Oligocene marine transgression (c. 25–35 Ma, the Oligocene drowning) and that all the land biota subsequently arrived by dispersal – including the poorly dispersing frogs.LocationNew Zealand.MethodsThe complete mitochondrial genome of the New Zealand native frog Leiopelma hochstetteri was sequenced, assembled and analysed, and compared with that of L. archeyi.ResultsUsing many phylogenetic analyses we examined the evolutionary relationships of the two species of Leiopelma, both for the deepest divergence within New Zealand and relative to other frogs. Our results give estimates of well over 65 Ma for the first divergence of leiopelmatid frogs within New Zealand, and over 150 Ma for the divergence of Leiopelma from its closest relative, the North American tailed frog Ascaphus truei.Main conclusionsThe identification of such a deep divergence among the extant Leiopelma species provides some of the strongest support yet for a mixed‐age model for the origin of New Zealand's terrestrial biota, where some elements are of vicariant origin and others have arisen by long‐distance dispersal. This contradicts a full drowning model and supports the view that there must have been some continuous land through the Oligocene.