Collaborative Research: Burrows as buffers: do microhabitat selection and behavior mediate desert tortoise resilience to climate change?

极端气候越来越超过生物体的生理阈值，限制了物种的分布，最终导致栖息地丧失。对这些变化的适应能力取决于环境特征、行为和生理之间的相互作用，使物种能够获得合适的小气候。生态系统工程师是通过建造洞穴等结构来改变环境的物种，这些结构可以提供更稳定的温度和湿度，缓冲居住者免受极端温度的影响。这些生物的行动不仅对它们自身的持久性很重要，而且对使其他物种能够获得合适的小气候也很重要。莫哈韦沙漠龟是一种生态系统工程师，它为躲避和筑巢而建造洞穴，部分原因是气候变化，它面临着灭绝的威胁。最小的乌龟生命阶段--卵、孵化的幼龟和幼龟--特别容易受到极端温度的影响，因为它们体型较小，改变环境的能力有限。这些生命阶段依赖于母体筑巢或小型哺乳动物洞穴的保护。该项目旨在了解沙漠龟如何通过创建洞穴来改变它们的环境，描述如何通过洞穴实现体温调节，并衡量洞穴在生命阶段缓冲气温上升的有效性，特别强调筑巢雌性龟和早期生命阶段。这项研究将提供有关每个生命阶段对极端气候的适应能力的新数据，并将为未来气候情景下特定生命阶段的物种分布模型提供信息，确定可能成为气候避难所的地点。这项工作将开发针对年级的教育模块和教室套件，整合活跃的沙漠龟保护研究，并将在当地课堂上实施这些模块。该项目还将为K-12教师、本科生、研究生和博士后实习生提供培训机会。该项目由环境生物学和综合组织系统部门和保罗·G·艾伦家族基金会共同参与的一项联合计划提供支持。这项研究采用机械方法来评估行为和生理灵活性在确定濒危沙漠龟在整个生命阶段对气候变化的适应能力方面的作用。莫哈韦沙漠龟是一种重要的生态系统工程师。这项研究旨在表征卵和母龟筑巢行为的温度敏感性；测试温度和湿度状态对幼龟洞穴使用、洞穴形态和体温的影响；量化野生龟不同年龄段行为和洞穴的热缓冲能力；并使用呼吸测量法表征温度对能量消耗、水分损失和热偏好的影响。这些研究将为特定生命阶段的机械生态位模型(MNM)提供关键的生理参数，以响应气候变化，以确定沙漠龟将持续到未来的最佳栖息地。最后，本研究将通过收集模型选择的地点的环境数据来检验MNM预测。通过确定气候保护区和核心保护区，这些模型将为未来莫哈韦沙漠龟恢复活动的重点地点提供信息，包括恢复和协助迁徙。更广泛地说，结果将与更广泛的洞穴物种和使用洞穴的共生生物体相关，并导致改进的经验和建模方法，以预测气候变化对这一不同有机体群体的影响。该奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

Climate extremes increasingly exceed physiological thresholds for organisms, constraining species distributions and ultimately leading to habitat loss. Resilience to these changes depends on interactions between environmental features, behavior, and physiology that enable species to access suitable microclimates. Ecosystem engineers are species that modify their environment by creating structures, such as burrows, which can provide more stable temperature and humidity, buffering occupants against temperature extremes. The actions of these organisms are important not only for their own persistence but to enable other species to access suitable microclimates. The Mojave desert tortoise is an ecosystem engineer that creates burrows for shelter and nesting and is threatened with extinction, in part due to climate change. The youngest tortoise life stages - eggs, hatchlings, and juveniles - are particularly vulnerable to temperature extremes due to their small size and limited ability to modify their environment. These life stages rely on maternal nest placement or small mammal burrows for protection. This project aims to understand how desert tortoises modify their environment through burrow creation, to characterize how thermoregulation is achieved via burrow use, and to measure the effectiveness of burrows to buffer against rising temperature across life stages, with a particular emphasis on nesting females and early life stages. This research will provide new data on the resiliency of each life stage to climate extremes and will inform life stage-specific models of species distribution under future climate scenarios, identifying sites that may become climate refugia. This work will develop grade-specific educational modules and classroom kits that integrate active desert tortoise conservation research and will implement these modules in local classrooms. This project will also provide training opportunities for K-12 teachers, undergraduate students, a graduate student, and a post-doctoral trainee. This project is being supported via a joint program involving the Divisions of Environmental Biology and Integrative Organismal Systems and the Paul G. Allen Family Foundation.This research takes a mechanistic approach to evaluate the role of behavioral and physiological flexibility in determining resilience to climate change for the endangered Mojave desert tortoise across life stages, an important ecosystem engineer. The research seeks to characterize temperature sensitivity of eggs and maternal nesting behavior; test the effects of temperature and hydric status on juvenile burrow use, burrow morphology, and body temperature; quantify the thermal buffering capacity of behavior and burrows across age classes in wild tortoises; and use respirometry to characterize temperature effects on energy expenditure, water loss and thermal preference. These studies will provide key physiological parameters for life stage-specific mechanistic niche models (MNMs) of response to altered climate to identify optimal habitat for desert tortoises that will persist into the future. Finally, this research will test MNM predictions by collecting environmental data from model-selected sites. By identifying climate refugia and core conservation areas, these models will inform future focal sites for Mojave desert tortoise recovery activities, including restoration and assisted migration. More broadly, results will be relevant for the extended group of burrowing species and commensal organisms that use burrows, and lead to improved empirical and modelling methods for forecasting the impacts of climate change on this diverse group of organisms.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.