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Effects of an Insecticide on Competition in Anurans: Could Pesticide-Induced Competitive Exclusion be a Mechanism for Amphibian Declines?

Distel, Christopher A.
http://rave.ohiolink.edu/etdc/view?acc_num=miami1280363910

Abstract Details

2010, Doctor of Philosophy, Miami University, Zoology.
Amphibian populations are experiencing global enigmatic declines. One proposed factor in declines is pesticide exposure; however, the mechanism has not been described because exposures are often sublethal to amphibians. My research addressed whether pesticide effects could interact with natural factors to cause competitive exclusion in amphibians. My first study addressed whether intraspecific or interspecific competition and insecticide exposure affected syntopic tadpole species (American toads and northern leopard frogs) differently. I also followed postmetamorphic toads and frogs into the terrestrial environment to elucidate any latent effects of the larval environment. There were asymmetric responses between species to both factors. Toad tadpole survival was reduced with either competition or insecticide exposure, but not with both stressors. Leopard frog tadpole survival responded only to intraspecific competitors. There were no latent effects on terrestrial growth or survival. However, larger leopard frog metamorphs were more likely to survive and be larger at spring emergence. My second study addressed intra- or interspecific competitor density and insecticide exposure on tadpole survival and development. Three-fold differences in density of competing species were compared with even numbers of each species. Insecticide exposure reduced tadpole survival of toads but not leopard frogs. Both species experienced reduced survival with increasing intraspecific density. There were no interactions between competitors and insecticide on either species’ survival, and neither was excluded. My third study addressed insecticide exposure through time. A three-stage stochastic population model was built to determine whether the insecticide-induced reductions in tadpole survival could lead to extirpation. Insecticide exposure did not increase the risk of extirpation unless background tadpole survival was already low. With predation, insecticide exposure could begin to increase extirpation risk at greater background survival rates, but these increased risks were still relatively small. Managers seeking to ameliorate any effects of insecticide exposure on wild anurans should consider the presence (though not necessarily density) of multiple anuran species, because more species appears to reduce survival risks. However, over time it appears that the insecticide’s effects may not be as strong as those of natural biotic stressors, so exposure may not increase extirpation risk.
Michelle Boone, PhD (Advisor)
M. Henry Stevens, PhD (Committee Member)
James Oris, PhD (Committee Member)
María González, PhD (Committee Member)
Craig Williamson, PhD (Committee Member)
73 p.
Agricultural Chemicals; Animals; Biology; Ecology; Environmental Science; Toxicology; Zoology
toad; frog; Bufo; Rana; complex life cycles; community ecology; aquatic food webs; carbaryl; carbamate; population model; multiple life stages

Recommended Citations

Citations

  • Distel, C. A. (2010). Effects of an Insecticide on Competition in Anurans: Could Pesticide-Induced Competitive Exclusion be a Mechanism for Amphibian Declines? [Doctoral dissertation, Miami University]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=miami1280363910

    APA Style (7th edition)

  • Distel, Christopher. Effects of an Insecticide on Competition in Anurans: Could Pesticide-Induced Competitive Exclusion be a Mechanism for Amphibian Declines? 2010. Miami University, Doctoral dissertation. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=miami1280363910.

    MLA Style (8th edition)

  • Distel, Christopher. "Effects of an Insecticide on Competition in Anurans: Could Pesticide-Induced Competitive Exclusion be a Mechanism for Amphibian Declines?" Doctoral dissertation, Miami University, 2010. http://rave.ohiolink.edu/etdc/view?acc_num=miami1280363910

    Chicago Manual of Style (17th edition)

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© 2010, all rights reserved.
This open access ETD is published by Miami University and OhioLINK.