Isozyme genetics and the phytogeny of Italian freshwater gobies (Teleostei: Gobioidei)

Although predominantly a marine group in the Atlantic/Mediterranean fish fauna, three species of exclusively freshwater gobies (Teleostei: Gobiidae) occur in Italy. These are Padogobius marltmsii of north Italy and parts of Croatia, P. nigricans from the Tyrrhenian catchment area of Tuscany and Lazio, and Knipowitschia punctatissima from north-eastern Italy. Using horizontal starch-gel electrophoresis, isozyme polymorphism in 12 enzymes encoded at 18 loci was investigated in these species and related euryhaline forms. Genetic distance, and morphological cladistic analysis, indicates that the Italian freshwater gobies do not form a monophyletic group, with the Padogobius species well separated from other taxa, and K. punctalissima closest to its morphological congener, the lagoonal K. panizzae . No close correlation was found between genetic variation and environmental heterogeneity.