A phylogeny and timescale for the living genera of kangaroos and kin (Macropodiformes:Marsupialia) based on nuclear DNA sequences

Abstract

Kangaroos and kin (Macropodiformes) are the most conspicuous elements of the Australasian marsupial fauna. The approximately 70 living species can be divided into three families: (1) Hypsiprymnodontidae (the musky rat kangaroo); (2) Potoroidae (potoroos and bettongs); and (3) Macropodidae (larger kangaroos, wallabies, banded hare wallaby and pademelons). Here we examine macropodiform relationships using protein-coding portions of the ApoB, BRCA1, IRBP, Rag1 and vWF genes via maximum parsimony, maximum likelihood and Bayesian methods. We estimate times of divergence using two different relaxed molecular clock methods to present a timescale for macropodiform evolution and reconstruct ancestral states for grades of dental organisation. We find robust support for a basal split between Hypsiprymnodontidae and the other macropodiforms, potoroid monophyly and macropodid monophyly, with Lagostrophus as the sister-taxon to all other macropodids. Our divergence estimates suggest that kangaroos diverged from Phalangeroidea in the early Eocene, that crown-group Macropodiformes originated in the late Eocene or early Oligocene and that the potoroid–macropodid split occurred in the late Oligocene or early Miocene followed by rapid cladogenesis within these families 5 to 15 million years ago. These divergence estimates coincide with major geological and ecological changes in Australia. Ancestral state reconstructions for grades of dental organisation suggest that the grazer grade evolved independently on two different occasions within Macropodidae.