Evolutionary and contemporary responses to habitat fragmentation detected in a mesic zone marsupial, the long‐nosed potoroo (Potorous tridactylus) in south‐eastern Australia

Abstract

AbstractAimOutside of Australia's Wet Tropics, studies of the biogeographical patterns of unglaciated Southern Hemisphere mesic environments are limited, and have primarily focused on herpetofauna. In this study mitochondrial DNA (mtDNA) and microsatellite (nuDNA) analyses were used to investigate the impact of biogeographical barriers on the evolutionary history of the widespread Australian marsupial Potorous tridactylus, as well as the effect of recent human‐mediated habitat fragmentation.LocationAustralia; Queensland, New South Wales, Victoria, and Tasmania.MethodsThree hundred and fifty‐four individuals from 39 sites (representing 16 regional populations) across the species range were assessed for mtDNA Control Region and microsatellite (10 loci) variation. Genetic diversity, phylogeographical relationships and population structure were examined, as well as evidence for isolation by distance and past population expansion.ResultsThree highly divergent and reciprocally monophyletic mtDNA lineages were resolved (two mainland, one Tasmanian). A deep phylogeographical break, not associated with any obvious biogeographical barrier, was present on the mainland. Within the northern mainland and Tasmanian lineages, sub‐structuring was coincident with the presence of physical barriers to gene flow. Fine‐scale structuring was also present, with regional populations highly differentiated.Main conclusionsThis study expands on previous studies of Australia's mesic biome. Major phylogeographical breaks were identified, that dated to the Miocene (within the mainland) and Pliocene (isolation of Tasmanian), and differed from those described for the region's herpetofauna in age or location. The major mainland break appears species specific within this topographically complex region of Australia. Tasmanian populations were isolated from the mainland well before the most recent flooding of Bass Strait. Minor phylogenetic breaks within Tasmanian and northern NSW were associated with known biogeographical barriers. An absence of sub‐structuring within the southern mainland lineage suggests extensive historical connectivity. The presence of regional population structure suggests that post‐European settlement, local populations have become isolated and differentiated.