Allozyme diversity of European freshwater crayfish of the genus Austropotamobius.

Data are reported on genetic variation at 30 enzyme loci in Austropotamobius crayfish from France, England, Italy, Spain, and the Balkans. Three population groups were detected, corresponding to A. torrentium, A. pallipes and A. italicus (sensu KARAMAN, 1962). Reproductive isolation between these three taxa was demonstrated in the field. Populations from England, France, and north-western Italy belong to A. pallipes sensu stricto, those from the rest of Italy, Spain, western Slovenia and north-western Croatia belong to A. italicus, whereas A. torrentium was found in the Balkans up to the Italian border. An average D-Nei of 0.30 was found between A. pallipes and A. italicus, while the average genetic distance between these two species and A. torrentium was D-Nei = 0.77. Populations of A. italicus from Spain and north-central Apennines were found to be genetically closely related (D-Nei = 0.05), not supporting a subspecific rank for these populations (A. j. lusitanicus). Marked interpopulation genetic diversity was observed both within A. italicus (average F-ST = 0.80, D-Nei up to 0.18), and within A. torrentium (average F-ST = 0.73, D-Nei UP to 0.14), comparable to that previously reported for A. pallipes. Such genetic heterogeneity appears mainly related to range fragmentations and subsequent recolonizations from multiple refugia during the last glacial events. Overall low values of genetic variability were found in the samples tested (e.g. H-e from 0 to 0.05), with the highest values in larger sized populations from less disturbed areas (e.g. in A. italicus from Spain and Slovenia). The genetic erosion observed in Austropotamobius populations stresses the need to restore their genetic variability, e.g. by controlled restocking, for successful programs of recovery and management of these endangered crayfish.