Genetic and morphological variation within the Red-cheeked Dunnart (Sminthopsis virginiae)

Hayley R Winter

Sminthopsis virginiae (the Red-cheeked dunnart) is a carnivorous, dasyurid marsupial found in four disjunct populations around the northern coast of Australia and Papua New Guinea. Similar to many other Australian marsupials it is hypothesised that S. virginiae has been negatively impacted by European colonisation. The species currently has three recognised subspecies, each occupying distinct geographic locations. Sminthopsis v. virginiae is thought to be found only in Queensland, S. v. rufigenis is distributed across Papua New Guinea and the Aru Islands, and S. v. nitela has populations in the Top End of the Northern Territory and in the Kimberley region of Western Australia. These subspecies definitions were based primarily on geographic location, and morphological distinctions that were not statistically tested. Previous molecular work has indicated these subspecies definitions may not be accurately representing the genetic diversity within the species. The current study aimed to undertake a comprehensive genetic and morphological review of S. virginiae to clarify relationships within the species. Six genes, three mitochondrial (CR, 12S and cytb) and three nuclear (omega-globin, IRBP, and bfib7), were sequenced to assess the genetic divergence among the S. virginiae populations and were used to interpret how genetic patterns relate to the biogeography of northern Australia. Skulls were qualitatively and quantitatively examined from across the entire distribution of the species, and a total of 28 cranial and 67 dental measurements were taken to investigate differences among the four disjunct populations, and between the sexes. Whole-body wet specimens were also examined. Maximum Likelihood and Bayesian analyses of the molecular data produced phylogenetic trees with strong support for the distinction of two clades, Eastern and Western. Within these clades, some sub structuring was present, most evident in the Western clade. Kimura two-parameter divergence calculations supported the distinction of these two clades and revealed a similar degree of divergence between the two geographic populations within each clade. The morphological results supported the distinction of up to four groups within S. virginiae, matching each of the disjunct populations. The results suggest a full taxonomic revision of S. virginiae incorporating type specimens is needed to clarify the subspecies boundaries, which is crucial for a sound understanding of the species and future conservation management.

Genetic and morphological variation within the Red-cheeked Dunnart (Sminthopsis virginiae)

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