Abstract
Detecting genes involved in local adaptation is challenging and of
fundamental importance in evolutionary, quantitative, and medical genetics. To
this aim, a standard strategy is to perform genome scans in populations of
different origins and environments, looking for genomic regions of high
differentiation. Because shared population history or population sub-structure
may lead to an excess of false positives, analyses are often done on multiple
pairs of populations, which leads to i) a global loss of power as compared to a
global analysis, and ii) the need for multiple tests corrections. In order to
alleviate these problems, we introduce a new hierarchical Bayesian method to
detect markers under selection that can deal with complex demographic
histories, where sampled populations share part of their history. Simulations
show that our approach is both more powerful and less prone to false positive
loci than approaches based on separate analyses of pairs of populations or
those ignoring existing complex structures. In addition, our method can
identify selection occurring at different levels (i.e. population or
region-specific adaptation), as well as convergent selection in different
regions. We apply our approach to the analysis of a large SNP dataset from low-
and high-altitude human populations from America and Asia. The simultaneous
analysis of these two geographic areas allows us to identify several new
candidate genome regions for altitudinal selection, and we show that convergent
evolution among continents has been quite common. In addition to identifying
several genes and biological processes involved in high altitude adaptation, we
identify two specific biological pathways that could have evolved in both
continents to counter toxic effects induced by hypoxia.
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