Genetic indicators of environmental stress in central mudminnow ( Umbra Limi ) populations exposed to acid deposition in the Adirondack Mountains

Horizontal starch gel electrophoresis was used to characterize the genetic structure of central mudminnow (Umbra limi) populations from acid stressed (low pH/high Al) and nonacid-stressed sites in the north branch of the Moose River (NBMR), New York, in order to determine if environmental shifts were accompanied by detectable shifts in genetic structure Central mudminnow populations in the NBMR were characterized by significantly (p ≥ 0 05) lower heterozygosity levels at stressed sites (H (mean number of heterozygotes per locus per individual) = 0 060 0 102) than reference sites (H = 0 130, 0 142) Additionally, several genetic loci demonstrated either consistent (isocitrate dehydrogenase, phosphogluconate dehydrogenase) or moderately consistent (glucose 6 phosphate isomerase 1 malate dehydrogenase-1, mannose-6 phosphate isomerase) genotypic shifts in comparisons between populations at reference and low pH/high Al sites Populations at acid stressed sites were characterized by higher frequencies of one particular allozyme, suggesting that environmental conditions were acting as a selective force In acute laboratory toxicity tests (pH, 4 5, Al, 7 5 mg/L), the most tolerant fish were significantly more genetically variable, indicating that genetic diversity may be beneficial to the survival of individual fish experiencing physiological stress