Shuman-Goodier Molly E, Singleton Grant R, Propper Catherine R
Department of Biological Sciences, Northern Arizona University, Flagstaff, AZ, 86001, USA.
International Rice Research Institute, DAPO Box 7777, Metro Manila, Philippines.
Ecotoxicology. 2017 Dec;26(10):1293-1304. doi: 10.1007/s10646-017-1854-8. Epub 2017 Sep 21.
Increased pesticide use in rice agricultural ecosystems may alter competitive interactions between invasive and native amphibian species. We conducted an experiment with two rice paddy amphibians found in Luzon, Philippines, the invasive cane toad (Rhinella marina) and the endemic Luzon wart frog (Fejervarya vittigera), to determine whether exposure to a common herbicide, butachlor, drives competitive interactions in favor of the invasive amphibian. Our results revealed that competition had a strong effect on the development of both species, but in opposing directions; Luzon wart frog tadpoles were smaller and developed slower than when raised alone, whereas cane toad tadpoles were larger and developed faster. Contrary to our predictions, development and survival of endemic wart frog tadpoles was not affected by butachlor, whereas invasive cane toad tadpoles were affected across several endpoints including gene expression, body size, and survival. We also observed an interaction between pesticide exposure and competition for the cane toad, where survival declined but body size and expression of thyroid sensitive genes increased. Taken together, our findings indicate that the success of the cane toad larvae in rice fields may be best explained by increased rates of development and larger body sizes of tadpoles in response to competition with native Luzon wart frog tadpoles rather than lower sensitivity to a common pesticide. Our results for the cane toad also provide evidence that butachlor can disrupt thyroid hormone mediated development in amphibians, and further demonstrate that important species interactions such as competition can be affected by pesticide exposure in aquatic ecosystems.
水稻农业生态系统中农药使用的增加可能会改变入侵两栖物种与本地两栖物种之间的竞争关系。我们对菲律宾吕宋岛发现的两种稻田两栖动物进行了一项实验，即入侵性的海蟾蜍（Rhinella marina）和本地的吕宋疣蛙（Fejervarya vittigera），以确定接触一种常见除草剂丁草胺是否会促使竞争关系朝着有利于入侵两栖动物的方向发展。我们的结果表明，竞争对这两个物种的发育都有强烈影响，但方向相反；吕宋疣蛙蝌蚪比单独饲养时更小且发育更慢，而海蟾蜍蝌蚪更大且发育更快。与我们的预测相反，本地疣蛙蝌蚪的发育和存活不受丁草胺影响，而入侵性海蟾蜍蝌蚪在包括基因表达、体型和存活等几个终点指标上受到了影响。我们还观察到农药暴露与海蟾蜍竞争之间的相互作用，即存活下降，但体型和甲状腺敏感基因的表达增加。综合来看，我们的研究结果表明，海蟾蜍幼虫在稻田中的成功可能最好解释为与本地吕宋疣蛙蝌蚪竞争导致蝌蚪发育速度加快和体型增大，而不是对常见农药的较低敏感性。我们对海蟾蜍的研究结果还提供了证据，表明丁草胺会扰乱两栖动物甲状腺激素介导的发育，并进一步证明了竞争等重要物种相互作用会受到水生生态系统中农药暴露的影响。
