Ecological and Evolutionary Impacts of Pesticides on Non-target Organisms: A Focus on Amphibians

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This project focuses on the role that ecological context plays in determining the impact of pesticides on non-target organisms in nature. The overall goal of this proposal is to determine the ecological and evolutionary effects of long-term exposure to a pesticide on amphibians, a group of global conservation concern. The first objective of the research is to examine effects of exposure time on lethality of pesticide exposure. For this preliminary objective, eight species of larval amphibians will be subjected to carbaryl, a common pesticide, for varying lengths of time. The second objective of this study is to determine how the biotic and abiotic ecological environment interacts with pesticide exposure to affect fitness traits. Laboratory studies suggest that changes in pH and the presence of predator cues can make pesticides much more deadly, but it is unknown if these dramatic effects occur under natural conditions. Additionally, the toxicological focus has been on lethal effects with less of a focus on nonlethal effects such as changes in individual traits. However, we know from ecological studies that trait changes can have dramatic effects on how an individual interacts with other species. To achieve the second objective, the investigator will rear larval amphibians in pond mesocosms and examine the interacting impacts of pesticides, pH, and predator cues on individual survival and individual traits. It is predicted that the inclusion of natural differences in ecological conditions will have a substantial impact on the pesticide-induced traits and pesticide-caused mortality. The third objective of this study is to examine the evolution of pesticide resistance in amphibians. There is a vast literature on evolved resistance in many pest species, but investigations of evolved resistance in non-target species are noticeably lacking and studies of evolved resistance in amphibians appear to be nonexistent. To investigate the process of evolved resistance in amphibians, the investigator will take a three-pronged approach that examines differences in resistance among populations that differ in historical pesticide exposure, the heritability of pesticide resistance, and a multi-generation selection experiment to determine if amphibians exposed to pesticides can eventually evolve resistance to pesticides. The expectation is that there is genetic variation in pesticide resistance in natural populations and exposure to pesticides will favor the evolution of resistance in amphibians. Collectively, this research is expected to show that ecological context is critical for understanding the ecological and evolutionary impacts of pesticides in non-target organisms.