Molecular evidence for the pattern and timing of cladogenesis in dasyurid marsupials

Abstract

Recent molecular studies have provided estimates of phylogeny for nearly all living and recently extinct species in the Order Dasyuromorphia, the dominant clade of insectivorous-carnivorous marsupials in Australasia. We review these studies along with morphology-based ones, and present an analysis of all cytochrome b, 12S rRNA, and protamine P1 gene sequences available. In light of these results, we provide a revised suprageneric classification and assess the implications of molecular and paleontological data for dasyurid cladogenesis. Molecular results divide extant dasyurids (Dasyuridae) into four major clades apart from the numbat (Myrmecobiidae) and thylacines (Thylacinidae). We recognize these clades as tribes Dasyurini (Dasyurus, Phascolosorex, and allied genera) and Phascogalini (Antechinus, Murexia, Phascogale) in the Subfamily Dasyurinae, and tribes Sminthopsini (Sminthopsis, Ningaui, Antechinomys) and Planigalini (Planigale) in the Subfamily Sminthopsinae. Each tribe shows a basal radiation of lineages corresponding to genera or species groups. Our results concur with the most recent previous synthesis of dasyurid phylogeny in many respects, but subsumption of New Guinean «phascolosoricines» and «muricines» within Dasyurini and Phascogalini, respectively, constitute significant differences. In particular, the sister-pairing of «phascolosoricines» with a Dasyurus–Sarcophilus clade implied by molecular data is difficult to reconcile with anatomy. Divergence rates of mitochondrial sequences are calibrated approximately by comparing thylacine-to-dasyurid distances with the age of the oldest thylacinid (Badjcinus, latest Oligocene). Estimated cladogenic dates suggest that extant subfamilies shared a common ancestor around 24 Mya and that major radiations began late in the mid-Miocene, consistent with the results of previous paleontological studies. The late-middle and late Miocene corresponds to an episode of faunal turnover in Australian marsupials (including the decline of thylacinid and bandicoot genera, as well as the rise of dasyurids) and to a time when uplift of the New Guinean highlands accelerated the transition from rainforest to drier habitats. Our findings are consistent with the hypothesis that continent-wide climate changes modulated macroevolution across these independent marsupial clades.