Molecular systematics of the enigmatic 'phascolosoricine' marsupials of New Guinea

Abstract

Previous analyses of DNA sequences for mitochondrial cytochrome-b and 12S rRNA, along with the nuclear protamine P1 genes, suggested that the New Guinean dasyurid genera Phascolosorex and Neophascogale (phascolosoricines) form the sister groups of quolls (Dasyurus) and Tasmanian devils (Sarcophilus). This runs counter to a common perception that phascolosoricines are anatomically primitive and only distantly related to other dasyurids. We report the DNA sequences of two additional mitochondrial loci (tRNA^Val and 16S rRNA) and nuclear loci (interphotoreceptor binding protein exon 1, beta-fibrinogen intron 7) from Phascolosorex dorsalis, Neophascogale lorentzii, and all but three other dasyurid species. These sequences, along with those previously published, comprise a dataset of 7053 nucleotides. Phylogenetic analyses indicate that phascolosoricines form a clade that is highly resolved as sister to Dasyurus + Sarcophilus. This result is obtained independently by mitochondrial and nuclear genes, and cannot be attributed to taxon- or gene-sampling bias, compositional heterogeneity, or the use of overly simplistic phylogenetic estimation procedures. A re-evaluation of published morphological data bearing on the relationships of phascolosoricines demonstrates that, although the conflict with molecular results is significant, it is limited to a small number of correlated dental features that show considerable homoplasy in their evolution.