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CHANGES IN GENETIC DIVERSITY OF A WHITE SUCKER POPULATION FOLLOWING EXPERIMENTAL WHOLE-LAKE ACIDIFICATION
Citation:
Bagley, M J., S A. Christ, K. H. Mills, AND S. M. Chalanchuk. CHANGES IN GENETIC DIVERSITY OF A WHITE SUCKER POPULATION FOLLOWING EXPERIMENTAL WHOLE-LAKE ACIDIFICATION. Presented at American Fisheries Society, Madison, WI, August 21-26, 2004.
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:
Despite great strides to reduce sulfur dioxide emissions over the last decade, acid precipitation remains a persistent threat to North American fish communities. A demographic analysis of white suckers in an experimentally acidified oligotrophic lake in northwest Ontario demonstrated complete recruitment failure in three years when the pH was between 5.0 and 5.2 and highly variable recruitment during subsequent recovery. We exploited archived fin rays that had been used for age analysis to evaluate genetic changes during the acidification (1976-1983) and recovery (1984-1996) phases of the experiment. We hypothesized that serial recruitment failures and high recruitment variability would create a population bottleneck, reducing genetic diversity relative to white suckers in a nearby reference lake. Allelic distributions at twelve microsatellite loci were evaluated for 1150 samples collected from the acidified lake and 745 samples from the control lake, representing year classes between 1957 and 1994. Surprisingly, genetic diversity greatly increased in the first year of acidificatiion and remained relatively stable thereafter. One locus which was intially monomorphic segregated for ten alleles following acidification. The observed changes in genetic diversity suggest that the most important effect of acidification may have been to reduce barriers to effective immigration into the lake.