Diversity of mitochondrial DNA of the endangered white-clawed crayfish (Austropotamobius italicus) in the Po River catchment

1. The strong contraction of the European populations of white-clawed crayfish has stimulated research of its population genetics. As part of a conservation project to introduce and improve Italian populations of Austropotamobius italicus, the genetic diversity of 16 populations from 10 tributaries of the Po River drainage was evaluated by sequencing a 494 bp length of cytochrome oxidase subunit I (COI mtDNA). 2. The evolutionary tree topologies and the parsimony network of 26 haplotypes separated into two clusters, on the basis of high average genetic distance (6.51 +/- 0.42%). This finding indicated the presence of distinct evolutionary lineages, other than different allopatric sources. 3. An ancestral haplotype (Nav) was identified and 13 haplotypes, found mainly as singletons, were independently connected to Nav by short branches with one mutation site. Unimodal mismatch distribution and the goodness-of-fit of the observed data reflected a model of sudden population expansion, after the last glacial bottleneck event. 4. A general moderate level of genetic variability (h = 0.22-0.7 and pi = 0.045-0.27%) was highlighted within A. italicus populations inhabiting Alpine and Apennine tributaries of the Po River. Analysis of molecular variance (AMOVA) revealed significant genetic structuring across all hierarchical levels, indicating that a major proportion of genetic variance is structured among localities within drainages. Multiple adjacent localities, strictly connected by the Po River, shared the two most frequent haplotypes (Nav and Laz), while remote populations, far from the Po River inflow, move towards a mtDNA fixation. 5. The results of this study indicate that distinct populations should be treated as separate entities for management. The key implication of the data is that ad hoc measures for successful programmes of recovery and management strategies for A. italicus conservation, such as the phylogeographic study of haplotype distribution at a local scale and the genetic variability of populations used as stock breeders, should be considered.