Biogeographical implications of climate change for an alpine mammal, the American pika

Le résumé fourni par la source

Anthropogenic climate change has already impacted a majority of species globally. The aim of this dissertation is to understand how climate and climate change influences animal ecology and evolution across space and time, using the American pika (Ochotona. princeps) as a model system. I investigate how pika body size, diet, and occupancy are influenced by different aspects of climate over space and time. Body size in O. princeps populations best correlates to precipitation and vegetation, rather than temperature. Our findings suggest that pika body size may be more related to vegetation and food availability than the direct effects of temperature. Then, to investigate the impacts of climate on pika diet across diverse spatiotemporal scales, I use stable isotope analysis (d13C and d15N) of pika bone and fur. Population mean isotope values correlate with local climate conditions: higher d15N values reflect hotter, more arid environmental conditions and d13C negatively correlates with humidity and precipitation. The isotopic dietary niche of pikas appears to be remarkably consistent given the extensive latitudinal and temporal extent of my study. At the trailing edge of their range, I examine the drivers of pika occupancy through field surveys. Pikas were most likely to have disappeared from sites with high vapor pressure deficit (low atmospheric moisture). My results suggest that aspects of moisture and precipitation are consistently influential factors in pika evolution and ecology. The relative inflexibility of pika isotopic niche and body size may contribute to pika’s ongoing decline in drier climates.

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