DAO 123:227-238 (2017)  -  DOI: https://doi.org/10.3354/dao03094

Complex interactive effects of water mold, herbicide, and the fungus Batrachochytrium dendrobatidis on Pacific treefrog Hyliola regilla hosts

John M. Romansic1,*, James E. Johnson2, R. Steven Wagner2, Rebecca H. Hill3, Christopher A. Gaulke4, Vance T. Vredenburg5, Andrew R. Blaustein1

1Department of Integrative Biology, 3029 Cordley Hall, Oregon State University, Corvallis, Oregon 97331, USA
2Department of Biological Sciences, Science Building, Room 338, 400 East University Way, Central Washington University, Ellensburg, Washington 98926-7537, USA
3Department of Fisheries and Wildlife, 104 Nash Hall, Oregon State University, Corvallis, Oregon 97331-3803, USA
4Department of Microbiology, 226 Nash Hall, Oregon State University, Corvallis, Oregon 97331, USA
5Department of Biology, 1600 Holloway Avenue, San Francisco State University, San Francisco, California 94132, USA
*Corresponding author:

ABSTRACT: Infectious diseases pose a serious threat to global biodiversity. However, their ecological impacts are not independent of environmental conditions. For example, the pathogenic fungus Batrachochytrium dendrobatidis (Bd), which has contributed to population declines and extinctions in many amphibian species, interacts with several environmental factors to influence its hosts, but potential interactions with other pathogens and environmental contaminants are understudied. We examined the combined effects of Bd, a water mold (Achlya sp.), and the herbicide Roundup® Regular (hereafter, Roundup®) on larval Pacific treefrog Hyliola regilla hosts. We employed a 2 wk, fully factorial laboratory experiment with 3 ecologically realistic levels (0, 1, and 2 mg l-1 of active ingredient) of field-formulated Roundup®, 2 Achlya treatments (present and absent), and 2 Bd treatments (present and absent). Our results were consistent with sublethal interactive effects involving all 3 experimental factors. When Roundup® was absent, the proportion of Bd-exposed larvae infected with Bd was elevated in the presence of Achlya, consistent with Achlya acting as a synergistic cofactor that facilitated the establishment of Bd infection. However, this Achlya effect became nonsignificant at 1 mg l-1 of the active ingredient of Roundup® and disappeared at the highest Roundup® concentration. In addition, Roundup® decreased Bd loads among Bd-exposed larvae. Our study suggests complex interactive effects of a water mold and a contaminant on Bd infection in amphibian hosts. Achlya and Roundup® were both correlated with altered patterns of Bd infection, but in different ways, and Roundup® appeared to remove the influence of Achlya on Bd.


KEY WORDS: Amphibian decline · Multipathogen · Sapronosis · Oomycete · Environmental stressor


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Cite this article as: Romansic JM, Johnson JE, Wagner RS, Hill RH, Gaulke CA, Vredenburg VT, Blaustein AR (2017) Complex interactive effects of water mold, herbicide, and the fungus Batrachochytrium dendrobatidis on Pacific treefrog Hyliola regilla hosts. Dis Aquat Org 123:227-238. https://doi.org/10.3354/dao03094

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