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Body Size Evolution of the American Pika (Ochotona princeps): GIS techniques to explore drivers of evolution

Marie Westover

Objectives:

* Determine if pikas populations have distinctly different body masses

* Identify which climatic variables are influencing body size of pikas

Ochotona princeps mitochondrial DNA lineages

adapted from Galbreath et al 2009

Climate change is predicted to alter the distributions of species around the world, in addition to other biological changes. Species have three options available when climate changes render their habitat unsuitable: they can move, adapt or become locally extirpated.

Pikas (Ochotna princeps) are small rabbit relatives that inhabit alpine areas of the western United States. Global warming appears to be negatively affecting their populations, and they have disappeared from parts of their range. They are listed by many states as vulnerable species or species of concern, but petitions to list them as endangered species have been rejected. The causes and extent of their decline are debated among biologists. Many biologists believe that pikas are limited by warmer summer temperatures because the animals can easily overheat. Given that pikas are thought to be temperature sensitive, it suggests that their populations will have physical adaptations to local or regional climate.

Body mass is an important physical trait to investigate in animals when considering temperature sensitivity and climate change. Many mammals demonstrate larger body mass at higher latitudes and cooler climates, a trend known as Bergmann’s rule. Larger animals have greater overall metabolic and resource demands, and are also better adapted to retain heat due to relatively small surface area to volume ratios. In contrast, smaller individuals can dissipate heat more efficiently and subside on less food.

Do pikas vary in body mass over their geographic range, and if so, what climatic variables are they responding to?

To answer these questions, I uploaded museum data of pika body size and localities into ArcMap, and overlaid the points onto climate and environmental raster data. I extracted data from the rasters to the pika specimen locations, which provided me with temperature, precipitation, plant productivity and elevation for each point. I created linear models to see correlations between environmental variables and body mass.

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Methods Results Conclusion Sources