| The importance of the interaction between the organism and the environment on the genetic structure of populations was investigated by measuring the effect of dispersal ability, isolation by distance and elevation, and the presence of a dam on the degrees of population differentiation of three freshwater fish species, Catostomus commersoni, Luxilus cornutus and Rhinichthys atratulus, in the same watershed. As expected, the organism-environment interaction was important, population subdivision was highest for R. atratulus, followed by L. cornutus and lowest for C. commersoni in a manner consistent with their increasing dispersal ability. In addition, population subdivision in L. cornutus and R. atratulus populations was positively correlated with increases in elevation and less so with the distance between populations but not at all correlated with distance or elevation for C. commersoni . Lastly, the overall genetic structure of each species was not related to the presence of the dam, possibly because of large population sizes and insufficient time for genetic drift to act. However, in C. commersoni and R. atratulus populations on either side of the dam exhibited the highest estimates of differentiation indicating the possibility of localized effects. |
