Cladogenetic events in two relict species of Stenasellidae (Crustacea, Isopoda) from Sardinia Island (Tyrrhenian Sea): a biochemical approach.

Allozymic variation was studied in seven populations of exclusively stygobitic relict isopods of the genus Stenasellus. Two of the seven populations belong to different species (S. nuragicus and S. assorgiai) and were sampled in their type localities, With the exception of a population from the Su Mannau cave, the remaining populations, of uncertain systematic position, were sampled in wells from southern Sardinia. Levels of genetic divergence and the pattern of inferred phylogenetic relationships allow us to confirm that S. nuragicus and S. assorgiai are valid species. The populations of uncertain systematic position are phylogenetically related to these two species. Phylogenetic relationships are discussed in relation to the divergence times deducible from genetic distance data in order to assess the congruence between evolutionary events and Sardinian palaeogeographical dynamics.