Variability and differentiation of microsatellites in the genus Dasyurus and conservation implications for the large Australian carnivorous marsupials

All four species of Australian quolls (Dasyurus species) have declined since European settlement in terms of both range and population numbers. Six highly polymorphic simple sequence repeats (CAn microsatellites) were used to estimate the genetic variability and population differentiation within and among twenty populations (including museum specimens from six populations), as a preliminary means of assessing population conservation status and relative levels of variability within members of the genus. Overall mean expected heterozygosity (HE) and corrected allelic diversity (A′) were highest among western quolls. Northern quolls, eastern quolls, and tiger quolls were not significantly different from each other in either measure. There were also significant differences in diversity among populations within species. Genetic differentiation was estimated by a number of methods and showed that the microsatellites used here were useful for defining differences both among species and populations. Allele frequency data were summarised by two-dimensional MDS, which was able to partition populations into distinct species clusters. Similarly, the assignment test was able to assign most individuals to both the correct species and population levels. Results of MDS and the assignment test may prove useful in forensic applications. Genetic distance and subdivision between pairs of populations were assessed by two means based on different mutation models for microsatellites: infinite alleles model (Nei's D, FST) and stepwise mutation model (Goldstein's δμ2, RST). Pairwise measures of population subdivision indicate that most populations should be conserved as separate management units. We discuss results of these analyses in terms of applications to conservation for each of the four Australian species of quoll and provide a genetic basis for future population monitoring in these species.