Patterns of genetic divergence in Chondrostoma lusitanicum Collares‐Pereira, in intermittent Portuguese rivers

Samples collected from throughout the range of Chondrostoma lusitanicum Collares-Pereira, were examined electrophoretically for patterns of variation at 24 presumptive gene loci. Thirteen loci were found to be polymorphic (frequency of the most common allele 0.95). There was high differentiation between rivers, especially in the southern populations of the Mira and the Arade catchments. This differentiation was associated with a low level of genetic variation and was thus interpreted in the light of past and present bottlenecks. The differentiation of C. lusitanicum is congruent with that already observed for another cyprinid species of the genus Leuciscus inhabiting the same catchments. This reinforces the hypothesis that the periodic drying-up of extensive sections of these rivers may lead to reduction in population sizes and subsequent differentiation. The level of genetic divergence of both the Mira and Arade populations of C. lusitanicum compared to all other populations sampled suggested a review of their conspecific status is necessary despite morphological similarity. The management implications in these rivers, and in the Tejo and Sado basins where C. lusitanicum is very rare, are discussed.