School of Natural Resources and the Environment, University of Arizona, Tucson, Arizona, 85721, USA.
National Park Service, Saguaro National Park, Tucson, Arizona, 85730, USA.
Ecol Appl. 2019 Apr;29(3):e01859. doi: 10.1002/eap.1859. Epub 2019 Feb 27.
Understanding how natural and anthropogenic processes affect population dynamics of species with patchy distributions is critical to predicting their responses to environmental changes. Despite considerable evidence that demographic rates and dispersal patterns vary temporally in response to an array of biotic and abiotic processes, few applications of metapopulation theory have sought to explore factors that explain spatiotemporal variation in extinction or colonization rates. To facilitate exploring these factors, we extended a spatially explicit model of metapopulation dynamics to create a framework that requires only binary presence-absence data, makes few assumptions about the dispersal process, and accounts for imperfect detection. We apply this framework to 22 yr of biannual survey data for lowland leopard frogs, Lithobates yavapaiensis, an amphibian that inhabits arid stream systems in the southwestern United States and northern Mexico. Our results highlight the importance of accounting for factors that govern temporal variation in transition probabilities, as both extinction and colonization rates varied with hydrologic conditions. Specifically, local extinctions were more frequent during drought periods, particularly at sites without reliable surface water. Colonization rates increased when larval and dispersal periods were wetter than normal, which increased the probability that potential emigrants metamorphosed and reached neighboring sites. Extirpation of frogs from all sites in one watershed during a period of severe drought demonstrated the influence of site-level features, as frogs persisted only in areas where most sites held water consistently and where the amount of sediment deposited from high-elevation wildfires was low. Application of our model provided novel insights into how climate-related processes affected the distribution and population dynamics of an arid-land amphibian. The approach we describe has application to a wide array of species that inhabit patchy environments, can improve our understanding of factors that govern metapopulation dynamics, and can inform strategies for conservation of imperiled species.
了解自然和人为过程如何影响具有斑块分布的物种的种群动态对于预测它们对环境变化的反应至关重要。尽管有相当多的证据表明，种群增长率和扩散模式会随时间变化，以响应一系列生物和非生物过程，但很少有关于复合种群理论的应用试图探索解释灭绝或定居率的时空变化的因素。为了便于探索这些因素，我们扩展了一个具有空间明确的复合种群动态模型，创建了一个仅需要二元存在-不存在数据的框架，对扩散过程的假设很少，并且考虑了不完全检测。我们将这个框架应用于低地豹蛙（Lithobates yavapaiensis）的 22 年的两年一次的调查数据，低地豹蛙是一种生活在美国西南部和墨西哥北部干旱溪流系统中的两栖动物。我们的结果强调了考虑控制转换概率时空变化的因素的重要性，因为灭绝和定居率都随水文条件而变化。具体来说，在干旱时期，局部灭绝更为频繁，特别是在没有可靠地表水的地点。当幼虫和扩散期比正常时期更潮湿时，定居率增加，这增加了潜在移民变态并到达邻近地点的可能性。在严重干旱期间，一个流域的所有地点的青蛙都灭绝，这表明了地点特征的影响，因为只有在大多数地点持续保持水和来自高海拔野火的沉积物量低的地区，青蛙才能存活。我们的模型的应用提供了关于气候相关过程如何影响干旱地两栖动物的分布和种群动态的新见解。我们描述的方法适用于广泛居住在斑块环境中的物种，可以提高我们对控制复合种群动态的因素的理解，并为保护濒危物种的策略提供信息。
