Cryptic genetic divergence in the giant Tasmanian freshwater crayfish Astacopsis gouldi (Decapoda: Parastacidae): Implications for conservation

The giant Tasmanian freshwater crayfish Astacopsis gouldi prized by fisherman, is the world's largest freshwater invertebrate. Astacopsis gouldi is known only from river drainages in northern Tasmania. A narrow distribution, pollution of habitat and over-harvesting has led to the rapid decline of populations and subsequent loss from a number of drainages. We collected mitochondrial DNA sequences to assess population structure and genetic diversity from throughout the species' distribution. We found a lineage from north-eastern Tasmania, which was genetically divergent compared with the remaining distribution in north-western Tasmania. Populations from the remaining distribution, including haplotypes found across a noted faunal barrier (Tamar River), were genetically homogeneous with