|SREL Reprint #2406|
GENETIC AND DEMOGRAPHIC RESPONSES OF MOSQUITOFISH (GAMBUSIA HOLBROOKI) POPULATIONS EXPOSED TO MERCURY FOR MULTIPLE GENERATIONS
CHRISTOPHER PAUL TATARA,1 MARGARET MULVEY,2 and MICHAEL C. NEWMAN2
of Georgia, Savannah River Ecology Laboratory, PO. Drawer E, Aiken, South
Carolina 29802, USA
(Received 22 December 1998; Accepted 22 April 1999)
Abstract-Genetic and demographic responses of mosquitofish were examined after multiple generations of exposure to mercury. Previous studies of acute lethal exposures of mosquitofish to either mercury or arsenic demonstrated a consistent correlation between time to death and genotype at the glucosephosphate isomerase-2 (Gpi-2) locus. A mesocosm study involving mosquitofish populations exposed to mercury for I I I d showed significant female sexual selection and fecundity selection at the Gpi-2 locus. Here the mesocosm study was extended to populations exposed to mercury for several (approx. four) generations. After 2 years, control and mercury-exposed populations met Hardy-Weinberg expectations and showed no evidence of genetic bottlenecks. The mean number of heterozygous loci did not differ significantly between the mercury-exposed and control populations. Significant differences in allele frequencies at the Gpi-2 locus were observed between the mercury-exposed and control populations. Relative to the initial and control allele frequencies, the Gpi-21111 allele frequency was lower, the Gpi-2 61 allele frequency increased, but the Gpi-211, allele frequency did not change in mercury-exposed populations. No significant differences were found in standard length, weight, sex ratio, or age class ratio between the control and mercury-exposed populations. Allele frequency changes at the Cipi-2 locus suggest population-level response to chronic mercury exposure. Changes in allele frequency may be useful as indicators of population response to contaminants, provided that the population in question is well understood.
Keywords-Genetics Mercury Allozymes Selection
SREL Reprint #2406
Tatara, C.P., M. Mulvey, and
M.C. Newman. 1999. Genetic and demographic responses of mosquitofish (Gambusia
Holbrooki) populations exposed to mercury for multiple generations.
Environmental Toxicology and Chemistry 18:2840-2845.