Fourteen years after the Shahid-Rajaei dam construction: an evaluation of morphometric and genetic differentiation between isolated up- and downstream populations of Capoeta capoeta gracilis (Pisces: Cyprinidae) in the Tajan River of Iran.

We evaluated the effects of the Shahid-Rajaei dam, 14 years after its construction, on morphometric and genetic divergence between up- and downstream populations of the Iranian fish Siah-Mahi (Capoeta capoeta gracilis). Sixty-six specimens were analyzed. There were significant differences between the 2 groups in the means of 16 morphometric characters (univariate analysis). In discriminant function analysis, the proportion of individuals classified into their original groups was 97 and 100% for up- and downstream populations, respectively. Principal component analysis of morphometric data demonstrated that the up- and downstream samples of Siah-Mahi are clearly distinct. In the genetic analysis, 6 informative primers produced 89 polymorphic bands with 95% polymorphism. In association analysis between morphological and genetic data, 63 of 89 genetic markers were significantly correlated with the 16 morphometric characters. We conclude that these are 2 morphologically and genetically distinct populations of C. c. gracilis, probably due to limited downstream dispersal and elimination of upstream migration.