Abstract

A new subspecies from the Sminthopsis murina complex, Sminthopsis griseoventer boullangerensis, subsp. nov., is described from Boullanger Island, off the coast of Western Australia. This subspecies was considered previously to be identical to S. griseoventer griseoventer, which is common on the mainland of south-western Western Australia, but differs from it with fixed differences at three of 18 isozymes screened. It also differs from S. griseoventer griseoventer in having a relatively longer tail and no entoconids on the second and third molars, and being completely separated from it in a canonical variates analysis. It has not been given full species status as it differs very little in mitochondrial DNA control region sequences from S. griseoventer griseoventer. It differs from other members of the S. murina complex in its grey ventral pelage, distinctive tail morphology, relatively small palatal vacuities (with correspondingly greater inter-palatal vacuity distance), relatively larger bullae, and more brachycephalic skull. Sminthopsis griseoventer boullangerensis has a small population and extremely limited known distribution, and is considered endangered. Potential threats include competition from a high-density population of house mice on Boullanger Island, the possibility of fires and feral predators being introduced to the island, and the increased risk of stochastic extinction that is consequent on small population size.