UBC Theses and Dissertations

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UBC Theses and Dissertations

Investigating the genetic basis of adaptation in a climate change sensitive species : the American pika Henry, Philippe O.


When faced with rapidly changing environmental onditions, wildlife species are left to adapt in situ, disperse or disappear. While it is commonly accepted that environmental changes are important drivers in shaping the evolutionary paths of organisms, the functional mechanisms of adaptations to changing environments are not fully understood. With the present thesis, I begin to investigate the relative importance of stochastic (genetic drift) versus deterministic (natural selection) processes in shaping genetic variation in the American pika (Ochotona princeps; Richardson, 1828). I begin by describing a novel and noninvasive sampling technique to collect hair from American pikas (Chapter 2). In that chapter, I test different DNA isolation techniques and identify the most promising approach, which was then used to extract DNA from a large number of samples distributed along three elevation gradients in the central Coast Mountains of British Columbia. In Chapter 3, I use a conservation genetic approach and microsatellite data to assess population genetic structure and gene flow among populations. In this chapter I found my populations to be genetically impoverished in comparison to populations from the centre of their range. The BC populations also exhibited limited gene flow, even among geographically proximate sites. Additionally, correlative analyses suggested that warm summer temperature limit pika dispersal across low elevation valley bottoms. In Chapter 4, I use Amplified Fragment Length Polymorphism (AFLP)-based genomic scans to shed light on the genetic basis of adaptation in this system. Based on a set of independent analyses including population genomic and landscape genomic approaches, I revealed that a small proportion (1.5%) of the genome displays evidence of natural selection. These outlier loci were found to differ among each elevation transect. Additionally, some loci that were under selection were also significantly associated with environmental variables such as mean annual precipitation and summer mean maximum temperature. This highlights the importance of these environmental variables in driving evolutionary adaptation in American pikas. Overall, the work presented here suggests that American pikas from the central Coast Mountains of BC will rely on local adaptations or plasticity in situ rather than range shifts to cope with changing climates.

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