ALLOZYMIC VARIATION OF THE ENDANGERED KILLIFISH APHANIUS-IBERUS AND ITS APPLICATION TO CONSERVATION

Genetic differentiation and patterns of variability in the endangered Iberian endemic, Aphanius iberus, were analyzed by allozyme electropho resis as a valuable database for conservation purposes. Genetic variab ility values expressed as heterozygosity (H = 0.015-0.097) were close to the values found in other members of Cyprinodontidae (H = 0.012-0.1 23). Polymorphism values (P = 0.125-0.542) were higher than reported i n the literature (P = 0.036-0.150) for Cyprinodontidae. Significant co rrelation existed between salinity values and genetic variability expr essed as heterozygosity (r = -0.76, p < 0.01) and polymorphism (r = -0 .60, p = 0.04). Low genetic variability values (H = 0.024-0.055, P = 0 .125-0.292) were exhibited by populations which inhabit salty lagoons. The highest values were found in populations occurring in marshes and irrigation channels (H = 0.051-0.097, P = 0.250-0.542). Associations among genetic, geographic and ecological parameters were tested using a Mantel test indicated that most of the genetic distances were explai ned by geographic distances but not by ecological factors, suggesting that isolation by distance could be the main factor explaining the dif ferentiation between sites. According to the genetic distances obtaine d, two main A. iberus groups were discernible: the Atlantic and Medite rranean. Genetic distances between both groups (DRogers = 0.179-0.261) were higher than values between recognized species of other cyprinodo ntids (DRogers = 0.11-0.27). On the basis of genetic distances we have dated the fragmentation of both populations to the Upper Miocene-Plio cene when most of the Mediterranean sea dried up. Subsequently, gene f low between Mediterranean and Atlantic populations was interrupted. Th e results of our genetic analyses suggested the existence of five oper ational conservation units (OCUs) for A. iberus. These units are defin ed as a continuous area limited by geographical boundaries, and inhabi ted by one or more populations sharing the same genetic pattern.