The effects of climate and demographic history in shaping genomic variation across populations of the Desert Horned Lizard ( Phrynosoma platyrhinos )

What is it about?

Species often experience different environments across their distribution. As a result, populations may become adapted to their local environment. However, local adaptation can be impeded by other population genetic processes such as migration and genetic drift. Genetic drift in particular can have a pronounced effect on the genetic structure during large geographic expansions where a series of founder effects leads to decreased variation in the direction of expansion. Here, we explore the genetic diversity of a desert lizard that occupies a wide range of environmental conditions and that has experienced post-glacial expansion along two colonization routes. We use a large SNP dataset to identify evidence that genetic variation is shaped by both climate and demographic history. Pronounced genetic differentiation was evident between populations occupying cold versus hot deserts, and we detected numerous loci with significant associations with climate. The genetic signal of founder effects, however, are still present in the genomes of the recently expanded populations, which comprise subsets of genetic variation found in the southern populations.

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Photo by Osman Rana on Unsplash

Photo by Osman Rana on Unsplash

Why is it important?

Understanding the processes that influence genetic variation is critically important in the current era of environmental change. This study leverages a large SNP dataset and recently developed methods to investigate such processes. Our findings highlight the importance of standing variation as a substrate that selection acts on and the alternative routes that selection can take when subsets of this variation are available.