GENETIC-VARIATION AND POPULATION SUBDIVISION OF THE ENDANGERED IBERIAN CYPRINID CHONDROSTOMA-LUSITANICUM

Products of 24 presumptive enzyme loci were used to analyse the consequences on genetic structure and variation of the Chondrostoma lusitanicum population decline within the Tejo basin. This rare cyprinid is endemic to the Iberian Peninsula and has a very restricted distribution. Five samples from the Tejo catchment were compared with a sample from a small basin, the Samarra, that has not suffered obvious anthropogenic pressures and where the fish is still abundant. Heterozygosity and polymorphism were higher overall in the Samarra. Several lines of evidence indicate a high degree of population subdivision within the Tejo basin. In fact, about half of the total gene diversity detected in the Tejo population was due to differences among samples. This differentiation appeared to be caused by genetic drift and possibly differential local selection, coupled with reduced gene flow among localities. The accelerated process of habitat degradation occurring in the lowland streams of the Tejo basin will lead to the inevitable reduction of intraspecies genetic diversity. Copyright © 1994, Wiley Blackwell. All rights reserved