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ENVIRONMENTAL INFLUENCES ON GENETIC DIVERSITY OF CREEK CHUBS IN THE MID-ATLANTIC REGION OF THE USA
Citation:
Christ, S A., M J. Bagley, AND F H. McCormick. ENVIRONMENTAL INFLUENCES ON GENETIC DIVERSITY OF CREEK CHUBS IN THE MID-ATLANTIC REGION OF THE USA. Presented at Using Science to Assess Environmental Vulnerabilities: a ReVA/MAIA Conference, Valley Forge, PA, May 13-15, 2003.
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:
Analysis of genetic diversity within and among populations of stream fishes may provide a powerful method for assessing the status and trends in the condition of aquatic ecosystems. We analyzed mitochondrial DNA sequences (590 bases of cytochrome B) and nuclear DNA loci (109 amplified fragment length polymorphisms, AFLP) of creek chub (Semotilus atromaculatus) populations from ten sites located in coal mining regions of Pennsylvania and West Virginia. This study represents the first phase of a larger study that will assess genetic diversity of multiple fish species throughout EPA's Mid-Atlantic Assessment Area (MAIA). Creek chub were strongly genetically differentiated, as the among-population component of genetic variance explained 71% of all mitochondiral diversity and 13% of nuclear DNA diversity. Genetic diversity within populations was assessed in relation to six independent environmental factors derived by principal component analysis (PCA) of 25 aquatic variables measured at each site. A PCA factor related to total nitrogen, phosphorous, and organic carbon content explained 51% of differences in the levels of mitochondrial diversity within populations, based on forward stepwise multiple regression. Three PCA factors explained 98% of the differences in nuclear DNA diversity within populations. The three factors were associated with latitudinal clines (43%) nitrogen/phosphorous/carbon (35%) and pH/ammonium (18%). A PCA factor related to geochemistry, which accounted for the most environmental variation, was not significantly associated with genetic diversity. These results provide evidence that environmental factors can strongly influence genetic diversity within populations, thus impacting their future vulnerability to environmental stresses.