Revised phylogeography of the common brushtail possum (<i>Trichosurus vulpecula</i>) reveals new insights into genetic structure across Australia

Abstract Understanding genetic relationships within species is essential for identifying distinct genetic lineages and informing conservation strategies, particularly for species with fragmented or widespread geographic distributions. One such widespread species that has suffered declines across Australia, despite remaining common in some areas, is the common brushtail possum (Trichosurus vulpecula), a nocturnal and arboreal marsupial. Previous genetic studies on brushtail possums had limited sampling, which has precluded a comprehensive assessment of the relationships within the species and genus. Using both single nucleotide polymorphism markers and the mitochondrial cytochrome b gene, this study employed phylogenetics, ancestry coefficients, and tested genetic differentiation, to examine the population structure of brushtail possums across Australia. Our results indicate that current subspecies’ classifications of T. vulpecula do not align with genetic structure, as Western Australian Pilbara and Midwest populations, currently defined as the subspecies Trichosurus vulpecula hypoleucus, are instead genetically similar to south-eastern and central T. v. vulpecula. These findings have important implications for current conservation strategies, including translocations of brushtail possums, and highlight the importance of comprehensive genetic sampling within wide-ranging species.