EAPSI: Adapting to Life with Less Water: Immune Function of Cane Toads in Semi-Arid Australia

自1935年首次引入澳大利亚以来，入侵甘蔗蟾蜍（Rhinella marina）一直在扩大它们的活动范围。它们固有的毒性导致数十种本地物种的数量急剧下降。根据它们的原生栖息地的温度和水的特征，人们认为它们的入侵将仅限于澳大利亚的热带地区。然而，它们的入侵正在迅速扩大，超出了假定的限度，这可能是逐渐适应干旱条件的结果。如果蔗蜍能够迅速进化到新的气候条件，那么它们的活动范围可能会远远超出之前认为的限制，从而威胁到非洲大陆的更大一部分。通过实地和实验室研究的结合，本项目将重点关注免疫系统，通过验证干旱入侵前线的蔗蜍为了保持有效的免疫功能而适应水分限制的假设，来评估蔗蜍的适应性。该项目将与澳大利亚悉尼大学著名的爬行动物和两栖动物生态学专家Rick Shine博士合作进行。本项目将采用生态免疫学方法评估甘蔗蟾蜍在澳大利亚的分布潜力。本研究将比较干旱入侵前线和中部地区蟾蜍的自然水合状态和免疫性能。这些结果将由一项实验室研究来补充，该研究将通过实验操纵来自两个地点的动物的水合状态，以确定来自澳大利亚半干旱地区的蟾蜍在脱水时是否会比来自澳大利亚更湿润地区的蟾蜍受到更少的抑制，甚至增强免疫功能。这些实验的结果将改变对这种入侵物种以及其他入侵物种的预测分布方式。该奖项由美国国家科学基金会和澳大利亚科学院共同资助，隶属于东亚和太平洋暑期研究所项目，支持美国研究生进行暑期研究。

Invasive cane toads (Rhinella marina) in Australia have been expanding their range since they were first introduced in 1935. Their inherent toxicity has resulted in dramatic population crashes of dozens of native species. Based on temperature and water characteristics of their native habitats, it was assumed their invasion would be restricted to tropical areas of Australia. However, their invasion is rapidly expanding beyond the presumed limits, and this may be a result of progressive adaptation to drier conditions. If cane toads can rapidly evolve to new climatic conditions, then their range expansion might exceed well beyond previously thought limitations and thus threaten a greater portion of the continent. Through a combination of field and laboratory studies, this project will focus on the immune system to evaluate the adaptability of cane toads by testing the hypothesis that cane toads at the dry invasion front are adapting a tolerance to water limitations in order to maintain effective immune function. This project will be conducted in collaboration with Dr. Rick Shine, a noted expert on the ecology of reptiles and amphibians, at the University of Sydney, Australia. This project will take an ecoimmunological approach to assess the distribution potential of cane toads in Australia. This study will compare naturally occurring hydration states and immune performances of toads from the arid invasion front with those from the mesic range core. These results will be complemented by a laboratory study that will experimentally manipulate the hydration state of animals from both sites to determine whether toads from semi-arid portions of Australia will have less suppressed or even enhanced immune function when dehydrated compared to toads found in more mesic areas of Australia where they were first introduced. The results of these experiments would transform the way distributions are predicted for this, and likely other, invasive species. This award under the East Asia and Pacific Summer Institutes program supports summer research by a U.S. graduate student and is jointly funded by NSF and the Australian Academy of Science.