Population genetic structure of island and mainland populations of the quokka, Setonix brachyurus (Macropodidae): a comparison of AFLP and microsatellite markers

Translocation and reintroduction are important tools for the conservation or recovery of species threatened with extinction in the wild. However, an understanding of the potential genetic consequences of mixing populations requires an understanding of the genetic variation within, and similarities among, donor and recipient populations. Genetic diversity was measured using two independent marker systems (microsatellites and AFLPs) for one island and four small remnant mainland populations of Setonix brachyurus, a threatened medium sized macropod restricted to fragmented habitat remnants and two off-shore islands in southwest Australia. Microsatellite diversity in the island population (R s = 3.2, H e = 71%) was similar to, or greater than, all mainland populations (R s = 2.1-3.9, H e = 34-71%). In contrast, AFLP diversity was significantly lower in the island population (PPL = 20.5; H j = 0.118) compared to all mainland populations (mean PPL = 79.5-89.7; mean H j = 0.23-0.29). Microsatellites differentiated all (mainland and island) populations from each other. However, AFLP only differentiated the island population from the mainland populations--all mainland populations were not significantly differentiated from each other for this marker. Given a known time since isolation of the island population from the mainland (6,000 years ago), and an overall more conservative rate of evolution of AFLP markers, our results are consistent with mainland populations fragmenting thousands of years ago (but