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GENETIC DIVERSITY AND STRUCTURE OF AN ESTUARINE FISH (FUNDULUS HETEROCLITUS) INDIGENOUS TO A HIGHLY CONTAMINATED URBAN HARBOR
Citation:
MCMILLAN, A. M., M. J. BAGLEY, S. A. JACKSON, AND D. E. NACCI. GENETIC DIVERSITY AND STRUCTURE OF AN ESTUARINE FISH (FUNDULUS HETEROCLITUS) INDIGENOUS TO A HIGHLY CONTAMINATED URBAN HARBOR. Ecotoxicology. Springer Science+Business Media, 15(6):538-548, (2006).
Impact/Purpose:
The objective of this task is to develop molecular indicators to evaluate the integrity and sustainability of aquatic fish, invertebrate, and plant communities (GPRA goal 4.5.2). Specifically, this subtask aims to evaluate methods for the measurement of:
fish and invertebrate community composition, especially for morphologically indistinct (cryptic) species
population genetic structure of aquatic indicator species and its relationship to landscape determinants of population structure (to aid in defining natural assessment units and to allow correlation of population substructure with regional stressor coverages)
genetic diversity within populations of aquatic indicator species, as an indicator of vulnerability to further exposure and as an indicator of cumulative exposure
patterns of temporal change in genetic diversity of aquatic indicator species, as a monitoring tool for establishing long-term population trends.
Description:
Intense directional selection on isolated populations can result in loss of genetic diversity, which if persistent, reduces adaptive potential and increases extinction probability. Phenotypic evidence of inherited tolerance suggests that toxic pollutants, specifically, polychlorinated biphenyls (PCBs), have acted as strong selective agents on wild populations of a non-migratory fish, Fundulus heteroclitus, indigenous to heavily contaminated sites. To evaluate population genetic structure and test for effects of intense, multi-generational PCB contamination on genetic diversity, we used AFLP (Amplified Fragment Length Polyorphism) analysis on fish collected from two sites within each of three regions along the east coast of North America that varied widely in PCB contamination. The sites included a heavily contaminated urban harbor (New Bedford, MA), an adjacent moderately contaminated sub-estuary (Buzzards Bay, MA), and an uncontaminated estuary about 60 km away (Narragansett, RI). AFLP markers distinguished populations at both moderate and small scales, suggesting potential limitations to gene flow at distances of two kilometers or less. No significant differences in genetic diversity were observed across the study sites. Therefore, despite limited gene flow and inferred strong selection by PCB contamination, we found no evidence of a population bottleneck. Genome-wide diversity may have been preserved because of large effective population sizes and/or because the mechanism for genetic adaptation to these contaminants affected only a small number of genetic loci. Alternatively, any loss in diversity may have been restored due to moderate levels of migration and relatively short generation time for this species.