SREL Reprint #1777
Impacts of toxicants on population dynamics and gene diversity in avian species
Ronald K. Chesser, Kevin B. Willis, and Nancy E. Mathews
Abstract: Computer simulation and mathematical modeling approaches were used to assess: (1) the relative effects of gradual vs rapid bioconcentration on rates of loss of genetic variation; (2) the recovery rates of avian populations after acute and chronic pesticide applications and the impact on loss of gene diversity; (3) the importance of timing (pre- and postmating) and mode (mortality vs fertility) of toxicant impacts on recovery rates and loss of genetic variation; and (4) the effectiveness of avian breeding and dispersal tactics in partitioning genetic variation within and among populations. Computer simulations of toxicant loads provided insight on cumulative effects of toxicants on population size and genetic variation. Gene diversity was shown to be more sensitive to rates of population recovery than to actual population sizes, and fertility reduction was much more important than mortality in maintenance of genetic variance and population size. Logistic models demonstrated that application schedules may have substantial impact on the recovery of population size and loss of genetic variation and that repeated acute impacts are of equal concern to chronic effects on population dynamics. Recovery rates are much quicker when impact is made primarily on adults rather than adults and juveniles concurrently. Additionally, toxicant impact that affects adult mortality rather than fertility will allow a more rapid rate of population recovery. Loss of gene diversity is inversely correlated to the recovery rate of the population. Thus, scenarios that prolonged the recovery rates of population sizes resulted in substantial losses in genetic variation. Genetic variance within populations was shown to conform to classical demic models. Results of the models are applicable to many avian species and document the need for careful consideration of the timing of toxicant applications to ensure population viability and variability.
Keywords: genetic variation, chronic exposure, fertility, mortality, population recovery
SREL Reprint #1777
Chesser, R. K., K. B. Willis, and N. E. Mathews. 1993. Impacts of toxicants on population dynamics and gene diversity in avian species. pp. 171-188 In: R. J. Kendall and T. E. Lacher, Jr. (Eds.). Proceedings of the Ninth Pellston Workshop: Wildlife Toxicology and Population Modeling. Integrated Studies of Agroecosystems. SETAC Special Publication Series. Lewis Publishers, Boca Raton, FL.
This information was provided by the University of Georgia's Savannah River Ecology Laboratory (srel.uga.edu).