RAPD and isoenzyme analysis of genetic variability in three allied species of catfish (Siluriformes: Pimelodidae) from the Tibagi River, Brazil

Genetic variability in three species of Pimelodidae catfish ( Iheringichthys labrosus , Pimelodus maculatus and Pimelodus cf. absconditus ), collected at four sites in the Tibagi river‐basin: Sertaneja, Londrina (lower Tibagi), Sapopema (middle Tibagi) and Tibagi (upper Tibagi) was analysed using RAPD and isoenzymatic techniques. Iheringichthys labrosus had the greatest genetic variability showing a proportion of mean polymorphic loci (P̄m) of 53.7+. The dendrogram showed that the individuals from the locations were clustered together, supporting the hypothesis that I. labrosus has a sedentary or localized geographical distribution. Pimelodus maculatus is the only species studied that is considered to be highly migratory. The P̄m obtained for this species was 30.2+. Their genetic dendrogram showed that the individuals were not clustered, based on the place of collection. P . cf. absconditus had a P̄m value of 47.4+, and the external morphology of this species is similar to that of I. labrosus , which hindered differentiation of individuals from the two species. RAPD and isoenzyme analysis, however, provided differential patterns for P . cf. absconditus from I. labrosus .