MICROSATELLITE AND MITOCHONDRIAL-DNA ASSESSMENT OF POPULATION-STRUCTURE AND STOCKING EFFECTS IN ARCTIC CHARR SALVELINUS-ALPINUS (TELEOSTEI,SALMONIDAE) FROM CENTRAL ALPINE LAKES

Despite geographical isolation and widespread phenotypic polymorphism, previous population genetic studies of Arctic charr, Salvelinus alpin us, have detected low levels of intra-and interpopulation variation. I n this study, two approaches were used to test the generality of low g enetic diversity among 15 Arctic charr populations from three major dr ainages of the central Alpine region of Europe. First, a representativ e subsample of each drainage was screened by PCR-RFLP analysis of mtDN A using 31 restriction enzymes. All individuals but one shared an iden tical haplotype. In contrast, microsatellite DNA variation revealed hi gh levels of genetic diversity within and among populations. The numbe r of alleles per locus ranged from six to 49, resulting in an overall expected heterozygosity from 0.72 +/- 0.09 to 0.87 +/- 0.04 depending on the locus. Despite evidence for fish transfers among Alpine charr p opulations over centuries, genetic diversity was substantially structu red, as revealed by hierarchical Phi, statistics. Eighteen per cent of total genetic variance was apportioned to substructuring among Rhone, Rhine, and Danube river systems, whereas 19% was due to partitioning among populations within each drainage. Cluster analyses corroborated these results by drainage-specific grouping of nonstocked populations, but also revealed damaging effects of stocking practices in others. H owever, these results suggest that long-term stocking practices did no t generally alter natural genetic partitioning, and stress the importa nce of considering genetic diversity of Arctic charr in the Alpine reg ion for sound management. The results also refute the general view of Arctic charr being a genetically depauperate species and show the pote ntial usefulness of microsatellite DNAs in addressing evolutionary and conservation issues in this species.