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

自1935年首次引入以来，澳大利亚的入侵甘蔗蟾蜍(Rhinella Marina)一直在扩大它们的活动范围。其固有的毒性已导致数十个本地物种的数量急剧下降。根据它们原生栖息地的温度和水特征，人们推测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，这可能是逐渐适应更干燥条件的结果。如果甘蔗蟾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部分。通过实地研究和实验室研究相结合的方式，该项目将重点放在免疫系统上，通过测试干旱入侵前线的甘蔗蟾蜍正在适应水分限制的假设来评估甘蔗蟾蜍的适应性，以保持有效的免疫功能。该项目将与澳大利亚悉尼大学爬行动物和两栖动物生态学著名专家里克·肖恩博士合作进行。该项目将采用生态免疫学的方法来评估甘蔗蟾蜍在澳大利亚的分布潜力。这项研究将比较来自干旱入侵前锋和中山岩心的蟾蜍自然发生的水合状态和免疫性能。这些结果将得到一项实验室研究的补充，该研究将对这两个地点的动物的水合状态进行实验操作，以确定与澳大利亚更中原地区的蛙相比，来自澳大利亚半干旱地区的蛙在脱水时是否会有较少的抑制，甚至是增强的免疫功能。这些实验的结果将改变对这种入侵物种以及可能还有其他入侵物种分布的预测方式。该奖项由东亚和太平洋夏季学院项目资助一名美国研究生的暑期研究，由NSF和澳大利亚科学院联合资助。

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.