polygenic adaptation
Hancock AM, Alkorta-Aranburu G, Witonsky DB & Di Rienzo A 2010 Adaptations to new environments in humans: the role of subtle allele frequency shifts. Phil Trans R Soc Lond B 365:2459-2468.
- we contrast the results of approaches based on haplotype structure and differentiation of allele frequencies to those from a method for identifying single nucleotide polymorphisms strongly correlated with environmental variables
- the first group of approaches tends to detect new beneficial alleles that were driven to high frequencies by selection
- the environmental correlation approach has power to identify alleles that experienced small shifts in frequency owing to selection
- the first group of approaches tends to identify only variants with relatively strong phenotypic effects
- the environmental correlation methods can detect variants that make smaller contributions to an adaptive trait
- additional modes of selection that are likely to apply to human populations include temporally and spatially varying selective pressures (Gillespie 1991)
- in cases in which selection pressures changed rapidly, selection on standing variation may have played an especially important role in adaptation
- one challenge for approaches that aim to assess the evidence of selection from correlations between population allele frequencies and environmental variables is that correlations could result from population structure alone
- an additional challenge is that subtle differences in allele frequencies due to environmental correlations may be masked by the geographical structure of human variation
- methods that control for these effects of population structure can overcome both types of problems
- the environmental correlation approach profoundly differs from previous selection scans because it uses multiple contrasts between populations that live in different environments while also controlling for population structure
