The distributions of species are determined by intrinsic factors such as physiological tolerances as well as extrinsic factors of the environment such as the availability of resources. While physiological tolerances generally change over evolutionary time scales, changes in environmental productivity due to processes such as succession or seasonal progression often occur over ecological times. I address both physiology and resource availability as drivers of the distributions and diversity of endothermic birds and mammals using a macroecological approach and a metabolic perspective. Migratory birds, altering communities over seasonal cycles, provide a unique opportunity to investigate the drivers of distributions and diversity that act over ecological time scales. In my first chapter, I show that energy use by migrants in North American breeding bird communities tracks the seasonal dynamics of resource availability. Migrants dominate consumption in tundra and boreal forests where the summer pulse of resources is large relative to winter productivity. While migrants are more prominent during the breeding season, many species overwinter throughout the temperate zone where their role in communities is understudied. In my second chapter, I quantify the contribution of migrants to diversity and energy use in North American winter bird communities. Overwintering migrants contribute little to diversity but dominate energy use in many temperate communities. My third chapter represents the efforts of myself and colleagues to understand the physiological adaptations that determine the thermal environments in which species can persist. By expanding on the Scholander-Irving model of heat transfer, we show that mass independent changes to basal metabolic rate and thermal conductance allow endotherms to inhabit nearly the full breadth of thermal environments on Earth.
Macroecology, metabolic ecology, birds, mammals, biogeography
Level of Degree
UNM Biology Department
First Committee Member (Chair)
Second Committee Member
Third Committee Member
Fristoe, Trevor S.. "Constraints on distributions and diversity of birds and mammals over variable environments." (2015). https://digitalrepository.unm.edu/biol_etds/39