Phylogeography of the Australian dunnart Sminthopsis crassicaudata (Marsupialia : Dasyuridae)

Analyses of mitochondrial DNA (mtDNA) and allozymes are used to investigate the population genetic structure, phylogeography and systematics of the fa t-tailed dunnart, Sminthopsis crassicaudata. Phylogenetic analyses of contr ol region sequences reveal the presence of two major mtDNA haplotype clades . A survey of the distribution of the two clades using diagnostic restricti on endonucleases shows that one clade is restricted to southeast Australia whereas the second clade occupies the remaining central to western range of S. crassicaudata. Allozyme electrophoresis also shows concordant patterns of population structure, with significant differences in allele frequency a t three loci between populations in the southeast and northwest. Together, the mtDNA and allozyme data provide evidence that S. crassicaudata consists of two Evolutionarily Significant Units (ESUs). The distribution of each E SU is not concordant with the distribution of the subspecies of S. crassica udata, and we propose that the current subspecies classification neither re flects the major genetic subdivisions present within S. crassicaudata nor w ould be appropriate for any future conservation management. The level of di vergence between mtDNA clades (3.4%) is indicative of cladogenesis in the P leistocene and reflects a long-term barrier to maternal gene flow between t hese two populations. One potential historical barrier was Lake Bungunnia, which persisted in the Murray basin over much of the Pleistocene.