Development of twenty-four novel microsatellite markers for the freshwater crayfish, Geocharax gracilis, using next generation sequencing

The crayfish Geocharax gracilis is an important inhabitant of natural and agricultural drainage systems in south-eastern Australia. To investigate population structure, genetic diversity and patterns of connectivity in natural and human-altered ecosystems, we isolated and characterised 24 microsatellite loci using next generation sequencing. Loci were initially tested for levels of variation based on 12 individuals from across the species' geographical range. A further 33 individuals from a single population were used to test for departures from Hardy-Weinberg equilibrium and linkage disequilibrium. We detected high to moderate levels of genetic variation across most loci with a mean allelic richness of 8.42 and observed heterozygosity of 0.629 (all samples combined). We found no evidence for linkage disequilibrium between any loci and only three loci (Geo01, Geo24 and Geo47) showed significant deviations from Hardy-Weinberg expectations. These same three loci, plus two additional loci (Geo06 and Geo28), also showed the presence of null alleles. These 24 variable markers will provide an important tool for future population genetic assessments in natural and human altered environments.