Identification of Genes under Selection in Interfertile, but Ecologically Divergent Oaks

Abstract

In the early stages of speciation with gene flow, divergent selection creates genomic regions with elevated levels of differentiation (outlier regions) interspersed by larger genomic regions that are homogenized by gene flow. Ecologically divergent, but interfertile oaks show such a pattern of genomic divergence and thus provide a system to identify outlier regions. The availability of a reference genome in oaks in the near future will allow us to anchor these outlier regions to the genome sequence and to identify genes with putative roles in adaptive divergence and reproductive isolation between species. Current advances in outlier screens in oaks with specific emphasis on American red oaks (section Lobatae) and comparative outliers across oak sections are reviewed. In addition, strategies are outlined to test for associations of nucleotide variation in putative outlier loci with adaptive traits that are involved in adaptive species divergence and reproductive isolation.