Phylogenetic Relationships of the Dasyurid Marsupial Genus Murexia

Five species of dasyurid marsupials endemic to New Guinea and herein referred to as Murexia longicaudata, M. rothschildi, M. habbema, M. naso, and M. melanurus have a varied taxonomic history. Until 1984, the latter 3 species had been assigned to the otherwise strictly Australian genus Antechinus, but comparisons of phallic morphology showed that this arrangement was untenable. Immunological and DNA hybridization studies of dasyurids suggested that New Guinean “antechinuses” were part of a clade that included M. longicaudata and M. rothschildi, a finding that was confirmed by early DNA sequence comparisons. Comprehensive analyses of cytochrome b, 12S rRNA, and protamine P1 sequences from all recognized dasyurid species led to the recommendation that these 5 species be included in a single genus (Murexia) that, along with Phascogale and Antechinus, constitutes the dasyurid tribe Phascogalini. Recently, however, a morphocladistic study concluded that these species are neither closely related to one another nor to any other dasyurid clade, placing them instead as successive basal branches within the family and assigning each to a distinct genus. Here we report results from an expanded DNA sequence data set that includes 2 additional mitochondrial loci (16S rRNA and control region) and 2 nuclear loci (beta-fibrinogen intron 7 and interphotoreceptor retinoid-binding protein exon 1) from phascogalin species and selected dasyurid and myrmecobiid outgroups. Phylogenetic analyses of these sequences show strong support for the monophyly of Murexia and its placement within Phascogalini, and provide the 1st resolved phylogeny of Murexia and Antechinus species. Reassessment of the morphological data suggests that the apparently primitive cranidental anatomy of Murexia may be an artifact of character polarizations or indicative of extreme homoplasy.