SREL Reprint #2621

 

 

 

Genetic and demographic responses of mercury-exposed mosquitofish (Gambusia Holbrooki) populations: Temporal stability and reproductive components of fitness

Christopher Paul Tatara1, Margaret Mulvey2, and Michael C. Newman2

1National Marine Fisheries Service, Manchester Research Station, PO Box 130, Manchester,
Washington 98353, USA
2The College of William and Mary, Virginia Institute of Marine Science, School of Marine Science,
Route 1208 Greate Road, Gloucester Point, Virginia 23062-1346, USA

Abstract: Two previous mesocosm studies showed changes in glucosephosphate isomerase-2 (Gpi-2) allele frequencies in mosquitofish populations exposed to mercury for 111 d or two years. A previous selection component analysis of single-generation populations exposed for 111 d to 18 µg/L Hg suggested that female sexual selection and fecundity selection could contribute to changes in Gpi-2 allele frequencies. The present multigeneration study was conducted to determine the stability of Gpi-2 allele frequencies over four years of mercury exposure, measure the reproductive fitness of Gpi-2 genotypes inhabiting control and mercury-contaminated mesocosms to determine a mechanism explaining changes in Gpi-2 allele frequencies, investigate differences in the demographic characteristics of mercury-exposed and control populations, and investigate the water quality of the mesocosms to determine if variables other than mercury show concordant patterns among mesocosms. Differences in Gpi-2 allele frequencies between control and mercury-exposed populations were stable over four years (~ eight generations) of mercury exposure. Mercury-exposed female mosquitofish had a lower probability of being gravid than control females (p=0.001). Mercury-exposed females also had lower fecundity (total number of eggs and embryos) than control females (p = 0.036). Unlike the results of the more intense mercury exposures in the single generation study, no strong evidence was found that Gpi-2 genotype influenced fecundity or the probability of being gravid in both control and mercury-exposed females. The quantification of fitness components is difficult but has the potential to enhance our understanding of how toxicants alter allele frequencies in exposed populations.

Keywords: Gambusia holbrooki, Genetics, Mercury, Selection, Fitness

SREL Reprint #2621

Tatara, C. P., M. Mulvey and M. C. Newman. 2002. Genetic and demographic responses of mercury-exposed mosquitofish (Gambusia Holbrooki) populations: Temporal stability and reproductive components of fitness. Environmental Toxicology and Chemistry 21:2191-2197.

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