Systematics, biogeography and ancestral state of the Australian marsupial genus Antechinus (Dasyuromorphia: Dasyuridae)

Since 2012 the number of recognized taxa in the Australian carnivorous marsupial genus Antechinus has increased from 10 to 15 species. The systematic relationships among these species and others in the genus are not well resolved. We undertook the first comprehensive, molecular systematic analysis of the genus, incorporating all known species and subspecies of Antechinus. Two mitochondrial (mtDNA) and four autosomal nuclear genes were sequenced. Four clades of Antechinus were consistently reconstructed in the concatenated and mtDNA analyses: (1) dusky antechinuses (A. arktos, A. swainsonii, A. vandycki and A. mimetes) and A. minimus; (2) A. godmani; (3) A. agilis, A. stuartii and A. subtropicus; (4) A. argentus, A. mysticus, A. adustus, A. flavipes, A. leo and A. bellus. The inclusion of A. adustus in clade 4 is surprising, because previous morphology-based studies suggested it was a member of clade 3. However, analysis of the nuclear dataset and multi-species coalescence analysis did not separate clades 3 and 4. Within clade 3, A. stuartii is not monophyletic and may be more appropriately classified as two species. Timing of cladogenesis is estimated for all 15 species of Antechinus, permitting us to posit an evolutionary scenario for the group. BEAST analysis dated the divergence of Antechinus from extant congeners to the Late Miocene and cladogenesis among all extant Antechinus to the Plio-Pleistocene. Wet, closed habitat was reconstructed as the most probable ancestral state for the genus Antechinus and the four main Antechinus clades. Overall, increasing aridity from the Miocene to the Pleistocene and a number of well-known biogeographic barriers to mesic species, appear to have driven speciation in Antechinus.