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Effects of pesticide mixtures on host-pathogen dynamics of the amphibian chytrid fungus

Buck, JC and Hua, J and Brogan, WR and Dang, TD and Urbina, J and Bendis, RJ and Stoler, AB and Blaustein, AR and Relyea, RA (2015) Effects of pesticide mixtures on host-pathogen dynamics of the amphibian chytrid fungus. PLoS ONE, 10 (7).

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Anthropogenic and natural stressors often interact to affect organisms. Amphibian populations are undergoing unprecedented declines and extinctions with pesticides and emerging infectious diseases implicated as causal factors. Although these factors often cooccur, their effects on amphibians are usually examined in isolation. We hypothesized that exposure of larval and metamorphic amphibians to ecologically relevant concentrations of pesticide mixtures would increase their post-metamorphic susceptibility to the fungus Batra-chochytrium dendrobatidis (Bd), a pathogen that has contributed to amphibian population declines worldwide. We exposed five anuran species (Pacific treefrog, Pseudacris regilla; spring peeper, Pseudacris crucifer; Cascades frog, Rana cascadae; northern leopard frog, Lithobates pipiens; and western toad, Anaxyrus boreas) from three families to mixtures of four common insecticides (chlorpyrifos, carbaryl, permethrin, and endosulfan) or herbicides (glyphosate, acetochlor, atrazine, and 2,4-D) or a control treatment, either as tadpoles or as newly metamorphic individuals (metamorphs). Subsequently, we exposed animals to Bd or a control inoculate after metamorphosis and compared survival and Bd load. Bd exposure significantly increased mortality in Pacific treefrogs, spring peepers, and western toads, but not in Cascades frogs or northern leopard frogs. However, the effects of pesticide exposure on mortality were negligible, regardless of the timing of exposure. Bd load varied considerably across species; Pacific treefrogs, spring peepers, and western toads had the highest loads, whereas Cascades frogs and northern leopard frogs had the lowest loads. The influence of pesticide exposure on Bd load depended on the amphibian species, timing of pesticide exposure, and the particular pesticide treatment. Our results suggest that exposure to realistic pesticide concentrations has minimal effects on Bd-induced mortality, but can alter Bd load. This result could have broad implications for risk assessment of amphibians; the outcome of exposure to multiple stressors may be unpredictable and can differ between species and life stages.


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Item Type: Article
Status: Published
CreatorsEmailPitt UsernameORCID
Buck, JC
Hua, J
Brogan, WR
Dang, TD
Urbina, J
Bendis, RJrjb94@pitt.eduRJB94
Stoler, AB
Blaustein, AR
Relyea, RA
ContributionContributors NameEmailPitt UsernameORCID
Date: 16 July 2015
Date Type: Publication
Access Restriction: No restriction; Release the ETD for access worldwide immediately.
Journal or Publication Title: PLoS ONE
Volume: 10
Number: 7
DOI or Unique Handle: 10.1371/journal.pone.0132832
Institution: University of Pittsburgh
Schools and Programs: Dietrich School of Arts and Sciences > Biological Sciences
Refereed: Yes
Date Deposited: 23 Aug 2016 14:24
Last Modified: 27 Mar 2021 09:55


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