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ALLOZYME ANALYSIS OF THE RELATIONSHIP AMONG CONTAMINANT-TOLERANT AND CONTAMINANT SENSITIVE POPULATIONS OF FUNDULUS HETEROCLITUS
Citation:
Roark, S. A., S. I. Guttman, AND D E. Nacci. ALLOZYME ANALYSIS OF THE RELATIONSHIP AMONG CONTAMINANT-TOLERANT AND CONTAMINANT SENSITIVE POPULATIONS OF FUNDULUS HETEROCLITUS. Presented at Society of Environmental Toxicology and Chemistry, Nashville, TN, November 12-16, 2000.
Description:
Genetic diversity is essential for adaptation to environmental change. Exposure to toxic chemicals causes directional selection that can reduce genetic diversity, rendering exposed populations less able to adapt to environmental change. Populations of the estuarine killifish Fundulus heteroclitus are abundant in the highly contaminated Superfund site in New Bedford Harbor (NBH), MA. In comparison with populations from less-contaminated sites, NBH populations exhibited heritable and significantly enhanced tolerance to PCB exposure in the laboratory. This study was conducted to determine whether PCB-adapted populations of F. heteroclitus exhibit reduced genetic diversity relative to PCB-sensitive populations, and to determine whether significant genetic differentiation exists among these populations. Four populations were sampled from sites in MA representing a gradient of pollution from the NBH Superfund site to the relatively less-contaminated West Island (WI). Two populations were sampled from clean sites in Point Judith Pond and the Narrow River in southern RI. Allozyme electrophoresis was used to determine genotype and allele frequencies at 13 protein-encoding loci for 31-56 individuals at each site. No significant genetic differentiation was observed among the four sites from MA. Highly significant (p<0.00005) genetic differentiation was observed between pooled MA sites and pooled RI sites at five of 10 polymorphic loci. Heterozygosity was higher at RI sites than at MA sites. These results suggest that high gene flow among theMA sites may limit genetic differentiation among populations despite strong selection for contaminant resistance in NBH. Field and laboratory studies are in progress to determine whether differences in allele frequencies and/or heterozygosity between MA and RI populations are related to environmental contaminants.