Speciation as a sieve for ancestral polymorphism

Abstract

Studying the process of speciation using patterns of genomic divergence between species requires that we understand the determinants of genetic diversity within species. Because sequence diversity in an ancestral population determines the starting point from which divergent populations accumulate differences (Gillespie & Langley 1979), any evolutionary forces that shape diversity within species can have a large impact on measures of divergence between species. These forces include those both decreasing (e.g., selective sweeps (Begun et al. 2007; Cruickshank & Hahn 2014) or background selection (Phung et al. 2016)) and increasing variation (e.g., balancing selection (Charlesworth 2006)). Selection can increase diversity by favoring the maintenance of polymorphism via overdominance, frequency dependence, and heterogeneous selection. Nevertheless, balanced polymorphisms are co ...