Three stream-dwelling fish species were used to investigate effects of ecology, life history, and water quality on genetic variation. We sampled Etheostoma caeruleum, E. blennioides, and Campostoma anomalum from six streams of varying water quality. Allozyme electrophoresis revealed that the most ecologically specialized species, E. caeruleum, was the least variable (P = 68.4%, Hobs = 1.2%). Etheostoma blennioides was intermediate in specialization and variation (P = 77.8%, Hobs = 7.8%), and the least specialized species, C. anomalum, had the most variation (P = 90.0%, Hobs = 12.1%). This pattern conforms to Willis' niche-variation hypothesis and Selander and Kaufman's adaptation model. Differences in ecology, life history, and amount of genetic variation are responsible for differences in how variation is apportioned within and among populations and within and among rivers. Populations in the river with the worst water quality (Huron River) had the lowest within-population variation for each species; therefore, genetic variation may be a useful indicator of water quality. Lower genetic variation may result from selection associated with specific loci, e.g., PGM-2, in stoneroller minnows. However, indirect effects on population size probably contributed to the erosion of genetic variation. Ecology, life history, and pollution tolerance data combine as predictors of species' risk of genetic erosion.
Individual diet variation in a marine fish assemblage: Optimal Foraging Theory, Niche Variation Hypothesis and functional identity
