CAREER: Individual-based species distribution models for understanding the demographic drivers of range shifts and their consequences for biodiversity

为了应对气候条件的变化，许多物种的地理分布，即物种范围，正在从低纬度地区消失，向高纬度地区转移（向两极转移）。虽然许多研究都集中在了解物种在其扩张的前沿地带的范围，在那里它们变得更加丰富，但很少有人重视理解为什么在低纬度的前沿地带，种群数量会下降。该项目关注的是在南部阿巴拉契亚山脉的尾缘发现的鸟类，并研究各种因素如何导致它们在其活动范围的边缘数量下降。具体来说，这项研究将测试以下因素的相对重要性：物种对极端温度和干旱的耐受性，与其他物种的竞争，食物来源和筑巢时间之间的不匹配，以及与种群规模小和运动模式有限相关的因素。鉴于环境条件的变化和物种分布的预期变化，本研究的结果将对物种保护和管理工作具有重要意义。该项目还将培训研究生和本科生开发不同的生态建模方法，将开发公民科学计划，并将使服务不足的高中STEM学生接触野外生态学。理论工作预测，不断变化的环境条件可以与生态过程相互作用，导致范围移动。然而，在解释这些分布变化时，经验研究未能确定物种耐受性和竞争、物候不匹配、密度依赖和分散限制等机制的相对贡献。本研究利用实验和观测数据来确定生理耐受和其他机制在解释阿巴拉契亚山脉南部低纬度范围内几种鸟类的种群动态中所起的相对作用。本研究将通过建立能够拟合经验数据的时空点过程模型，克服物种分布模型在理解范围变化方面的局限性。这一框架的独特之处在于，它能够在多个时空尺度上描述和预测生态过程，同时考虑到人口比率的个体差异。这项研究将促进对范围变化的科学认识，将为整合理论和应用生态学提供一个新的框架，并将开发预测模型，为生物多样性保护提供信息。

In response to changing climatic conditions, the geographic distribution of many species, i.e., species ranges, are shifting to higher latitudes (towards the poles) as they are disappearing from lower latitudes. While much research has focused on understanding species ranges at their expanding, leading-edges where they are becoming more abundant, less emphasis has been placed on understanding why populations would be declining at their lower latitude, trailing-edges. This project focuses on bird species found at their trailing-edges in the southern Appalachian Mountains, and examines how a variety of factors may contribute to their decline in numbers at this edge of their range. Specifically, this research will test the relative importance of: species tolerance to extreme temperatures and drought, competition with other species, mismatches between the availability of food sources and nesting times, and factors associated with having small population sizes and limited movement patterns. The results of this study will be important in efforts to conserve and manage species given changing environmental conditions and expected changes in the distributions of species. This project will also train graduate and undergraduate students in the development of different ecological modeling approaches, will develop a citizen sciences program, and will expose underserved high school STEM students to field ecology. Theoretical work predicts that changing environmental conditions can interact with ecological processes to cause range shifts. Empirical studies have, however, failed to identify the relative contributions of species tolerances and mechanisms such as competition, phenological mismatches, density-dependence, and dispersal limitations in explaining these distributional shifts. This study uses experimental and observational data to determine the relative role physiological tolerances and other mechanisms play in explaining the population dynamics of several bird species found at their low-latitude range limits in the southern Appalachian Mountains. This study will overcome the limitations of species distribution models for understanding range shifts by developing novel spatio-temporal point process models that can be fitted to empirical data. This framework is unique in its ability to describe and predict ecological processes at multiple spatial and temporal scales while accounting for individual variation in demographic rates. This research will advance scientific understanding of range shifts, will produce a new framework for integrating theoretical and applied ecology, and will develop predictive models to inform the conservation of biodiversity.