BIOCHEMICAL SYSTEMATICS AND BIOGEOGRAPHICAL PATTERNS OF THE ITALIAN AND CORSICAN SPECIES OF THE PROTONEMURA-CORSICANA SPECIES GROUP (PLECOPTERA, NEMOURIDAE)

The Protonemura corsicana species group shows an interesting Circummed iterranean-Caucasian distribution, with several relict or insular spec ies. Eight populations belonging to four species of this group and six populations belonging to Isoperla insularis (Morton) were studied by means of electrophoresis, performed on horizontal starch-gel. Samples were screened for variation at 17 presumptive loci and genetic diverge nce was calculated. Phenetic treating of allozymic data does not seem to support the theory of a Miocenic colonization of the Mediterranean basin. bn the contrary the cladistic approach is not congruent with th e phenetic methods and could be in agreement with a Miocenic vicarianc e hypothesis. Biogeographical patterns based on the systematic arrange ment obtained are discussed. The validity of electrophoretic methods i n revealing species relationships and boundaries is discussed.