ISOZYME GENETICS AND THE PHYLOGENY OF ITALIAN FRESH-WATER GOBIES (TELEOSTEI, GOBIOIDEI)

Although predominantly a marine group in the Atlantic/Mediterranean fi sh fauna, three species of exclusively freshwater gobies (Teleostei: G obiidae) occur in Italy. These are Padogobius martensii of north Italy and parts of Croatia, P. nigricans from the Tyrrhenian catchment area of Tuscany and Lazio, and Knipowitschia punctatissima from north-east ern Italy. Using horizontal starch-gel electrophoresis, isozyme polymo rphism in 12 enzymes encoded at 18 loci was investigated in these spec ies and related euryhaline forms. Genetic distance, and morphological cladistic analysis, indicates that the Italian freshwater gobies do no t form a monophyletic group, with the Padogobius species well separate d from other taxa, and K. punctatissima closest to its morphological c ongener, the lagoonal K. panizzae. No close correlation was found betw een genetic variation and environmental heterogeneity.