Systematic affinities of island and mainland populations of the Dunnart Sminthopsis griseoventer in Western Australia: data from allozymes and mitochondrial DNA

Abstract

The systematic affinities of Boullanger Island and Western Australian mainland populations of the Grey-bellied Dunnart Sminthopsis griseoventer were investigated using allozyme electrophoresis and phylogenetic analysis of a 404 bp region of the mitochondrial DNA (mtDNA) control region. Forty-six allozyme loci were screened for variation and found to be monomorphic in S. griseoventer from both Boullanger Island and one mainland population. Low levels of variation were also detected in the control region sequence, with just one haplotype observed among eight island individuals and three haplotypes among 10 mainland individuals, each differing at between two and four nucleotide sites (0.5?1.0% divergence). Phylogenetic analyses using maximum parsimony of control region sequence from mainland and island taxa, and four species of the "murina complex", S. aitkeni, S. murina, S. gilberti and S. dolichura, indicated that the island and mainland taxa formed a monophyletic group to the exclusion of the other "murina complex" species, but were paraphyletic at the level of the individual haplotypes. These results are consistent with the hypothesis that mainland and island populations of S. griseoventer comprise a single species, and suggest that there has been no long-term barrier to gene flow between these populations. Analyses of molecular variation provided evidence the island population represents a separate management unit for conservation, but are insufficient to determine whether there has been inbreeding or a recent bottleneck in the island population.