GENETIC-VARIATION AND DIVERGENCE OF LEUCISCUS-PYRENAICUS AND LEUCISCUS-CAROLITERTII (PISCES, CYPRINIDAE)

The taxonomy of the genus Leuciscus in the Iberian Peninsula has been presented on the basis of morphological analysis. Two species are beli eved to occur in Portuguese inland waters, L. carolitertii, the northe rn basins chub, and L. pyrenaicus, which was described for the Tejo an d southern basins. Since only slight differences in the meristic and m orphometric characters are observed, the distinction between the two s pecies has been made previously mainly on the basis of osteology. In o rder to investigate the patterns of genetic differentiation between th ese species, 24 sites were sampled for both species, and examined elec trophoretically for the study of variation at 27 presumptive loci. The results pointed to different levels of population differentiation amo ng drainages and support the recognition of the species level for L. p yrenaicus and L. carolitertii. Our results also suggested that the dis tribution area of L. pyrenaicus is probably restricted to Tejo and to the small drainages near Tejo, while L. carolitertii seems to have a w idespread distribution area, including Lima, Douro, Vouga, Mondego, Gu adina and Sado drainages. Moreover, concerning the southern population s, Mira and Arade, the surprisingly high level of differentiation obse rved al several loci, supports the existence of a further species occu rring in these small drainages. The evolutionary aspects related to th at differentiation are discussed. (C) 1995 The Fisheries Society of th e British Isles