Morphological and genetic variation in four Italian populations ofLebias fasciata(Teleostei, Cyprinodontidae)

Morphological and genetic analyses in four Italian populations of Lebias fasciata were carried out in order to assess the level of differentiation among populations. Fourteen meristic and 23 morphometric characters, relative to the skull, vertebral column, and the rays of the dorsal and anal fins were examined. In addition, variations at seven gene loci were investigated by allozyme electrophoresis. Both morphological and genetic results showed a noteworthy differentiation among the four populations which reflects their high degree of isolation. Allozyme results indicated that genetic variation is consistent with geographical distribution of these populations, while morphological differentiation cannot be interpreted biogeographically. The lack of dispersion phases in the life cycle of L. fasciata and its limited potential for gene flow account for the genetic divergence among populations. The inconsistency between morphological and genetic results for the two Sicilian populations may account for appreciable environmental (non‐genetic) influences on the morphological characters examined, which may obscure any enzyme‐morphological relation.