Collaborative Research: Linking Climate, Disease, and Demography To Understand Extinction Risks in Ectotherms

变温动物是像两栖动物、昆虫和植物这样的生物，它们的代谢过程，包括免疫系统功能，在很大程度上受环境温度的控制。因此，气候可以强烈地影响变温寄主与其病原体之间的相互作用。近几十年来，两栖动物种群受到疾病的严重影响，许多物种现已灭绝。该项目的一个主要目标是建立数学模型，帮助我们理解和预测气候变化将如何影响疾病爆发的严重程度，以及我们是否预计疾病会导致变温动物的长期数量下降。要做到这一点，我们必须建立模型，将气候对影响病原体传播的宿主特征的影响，以及气候对宿主繁殖时间和成功的影响结合起来。在这个项目中，我们建立了这样的模型，我们通过实验和实地观察蝾螈宿主和流行的虎纹Ambystoma tigrinum病毒来测试模型。根据这些数据测试我们的模型将有助于我们缩小气候对疾病和人口丰度的长期模式影响最大的方式。然后，我们可以使用我们经过良好测试的模型来预测气候变化如何影响未来的疾病和宿主种群稳定性。我们还将与州和联邦野生动物机构的合作者合作，以更好地了解虎纹Ambystoma tigrinum病毒对天然两栖动物种群的威胁。此外，我们将通过创建和完善一个项目来增加历史上服务不足的群体对科学的参与，该项目从服务不足的人群中招募本科生，培训这些学生撰写拨款和科学假设检验，并将他们纳入我们的研究团队，在那里他们将寻求回答补充问题。我们还将建立基于网络的建模资源，使公众可以在了解气候和疾病对全球变温动物种群的影响的同时，操纵我们的疾病动态模型的版本。致命病原体经常调节宿主种群丰度随时间的波动，这可能导致宿主种群数量下降，局部灭绝，甚至物种灭绝。对于异温寄主物种，气候调节影响寄主人口统计和病原体传播的特性，因此气候可以调节疾病如何影响寄主种群动态。然而，关键的知识缺口阻碍了对气候变化如何与疾病相互作用从而导致宿主数量长期波动的可靠预测。我们最终需要更强大的宿主-病原体模型来预测宿主种群对疾病和气候的长期动态反应，并结合这一理论的强大测试。在这里，我们建立了新的宿主-病原体模型，更现实地描述了气候如何同时影响传播，宿主人口统计和宿主物候。此外，我们的模型允许寄主个体对环境中的温度波动做出特殊的反应。这很重要，因为我们假设疾病爆发的规模和人口下降的风险最终取决于温度是否控制宿主个体之间特征变化的程度。为了验证我们的理论发展，我们进行了实验室实验，并观察了蝾螈病毒系统中的自然疾病爆发。我们还遵循一个总体的贝叶斯框架来估计模型参数并比较竞争模型，这使我们能够确定对解释该领域大规模模式最重要的特定气候依赖机制。然后，我们使用我们久经考验的模型来预测气候变化和病毒性疾病将如何改变美国西南部蝾螈的未来种群动态。我们还将制定一个本科生外展计划，以加强对STEM领域的参与。具体来说，我们将与北亚利桑那大学的包容性社区平等合作伙伴（EPIC）项目合作，为在STEM领域代表性不足的学生创建一个资助写作研讨会。最后，我们将建立一个门户网站，广泛传播我们的工作成果，让公众与图形模型的输出互动，并探讨气候变化和疾病对不同生态区域两栖动物种群的影响。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

Ectotherms are organisms like amphibians, insects, and plants, whose metabolic processes, including immune system functioning, are largely controlled by environmental temperature. Climate can therefore strongly influence the interactions between ectotherm hosts and their pathogens. In recent decades, amphibian populations have been strongly impacted by disease and many species are now extinct. A primary goal of this project is to build mathematical models that help us understand and predict how a changing climate will influence the severity of disease outbreaks, and whether we expect disease to lead to long-term population declines in ectotherms. To do this, we must build models that incorporate the effect of climate on host traits that influence pathogen transmission, as well as the effect of climate on the timing and success of host reproduction. In this project we build such models, and we test the models using experiments and field observations of a salamander host and the prevalent Ambystoma tigrinum virus. Testing our models against these data will help us narrow down the ways in which climate most strongly impacts disease and long-term patterns of population abundance. Then, we can use our well-tested models to make forecasts of how a changing climate might affect disease and host population stability in the future. We will also work with collaborators in state and federal wildlife agencies to better understand the threat of Ambystoma tigrinum virus to natural amphibian populations. Moreover, we will work to increase the participation of historically underserved groups in science by creating and refining a program that recruits undergraduates from underserved populations, trains these students in grant writing and scientific hypothesis testing, and incorporates them as members of our research team, where they will seek to answer complementary questions. We will also build web-based modeling resources in which the general public can manipulate versions of our disease dynamics models while learning about the effects of climate and disease on ectotherm populations across the world. Lethal pathogens often regulate how host population abundances fluctuate over time, which can cause host population declines, local extirpation, and even species extinctions. For ectothermic host species, climate regulates traits that affect host demography and pathogen transmission, such that climate can mediate how disease affects host population dynamics. Yet key knowledge gaps impede reliable predictions of how a changing climate will interact with disease to drive long-term fluctuations in host abundance. We ultimately require more robust host-pathogen models that forecast long-term host population dynamics in response to disease and climate, combined with robust tests of this theory. Here we build novel host-pathogen models that more realistically describe how climate simultaneously affects transmission, host demography, and host phenology. Further, our models allow host individuals to respond idiosyncratically to temperature fluctuations in the environment. This is important because we hypothesize that the size of disease outbreaks and the risk of population declines are ultimately determined by whether temperature controls the degree to which traits vary among host individuals. To test our theoretical developments, we conduct laboratory experiments and observe natural disease outbreaks in a salamander-virus system. We also follow an overarching, Bayesian framework to estimate model parameters and compare competing models, which allows us to identify the specific climate-dependent mechanisms that matter most for explaining large-scale patterns in the field. We then use our well-tested model to project how a changing climate and viral disease will alter the future population dynamics of salamanders in the US Southwest. We will also develop an undergraduate outreach program to enhance engagement in STEM fields. Specifically, with the Equal Partners in Inclusive Community (EPIC) program at Northern Arizona University, we will create a grant-writing workshop for students who are under-represented in STEM. Finally, we will develop a web portal to broadly disseminate the results of our work, which will allow the public to interact with graphical model output and explore the effects of climate change and disease on amphibian populations in different ecoregions.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.