| 英文摘要: | 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. |