title: Selection and genomic differentiation during ecological speciation: isolating the contributions of host association via a comparative genome scan of Neochlamisus bebbianae leaf beetles.
abstract: This study uses a comparative genome scan to evaluate the contributions of host plant related divergent selection to genetic differentiation and ecological speciation in maple- and willow-associated populations of Neochlamisus bebbianae leaf beetles. For each of 15 pairwise population comparisons, we identified "outlier loci" whose strong differentiation putatively reflects divergent selection. Of 447 AFLP loci, 15% were outliers across multiple population comparisons, and low linkage disequilibrium indicated that these outliers derived from multiple regions of the genome. Outliers were further classified as "host-specific" if repeatedly observed in "different-host" population comparisons but never in "same-host" comparisons. Outliers exhibiting the opposite pattern were analogously classified as "host-independent." Host-specific outliers represented 5% of all loci and were more frequent than host-independent outliers, thus revealing a large role for host-adaptation in population genomic differentiation. Evidence that host-related selection can promote divergence despite gene flow was provided by population trees. These were structured by host-association when datasets included host-specific outliers, but not when based on neutral loci, which united sympatric populations. Lastly, three host-specific outliers were highly differentiated in all nine different-host comparisons. Because host-adaptation promotes reproductive isolation in these beetles, these loci provide promising candidate gene regions for future molecular studies of ecological speciation.
authors.affiliation: Department of Biological Sciences, Vanderbilt University, Nashville, TN 37235, USA. scott.p.egan@vanderbilt.edu
authors.forename: Scott P
authors.initials: SP
authors.lastname: Egan
authors.forename: Patrik
authors.initials: P
authors.lastname: Nosil
authors.forename: Daniel J
authors.initials: DJ
authors.lastname: Funk
mesh_terms: D054458:Amplified Fragment Length Polymorphism Analysis; D000818:Animals; D001517:Coleoptera / Q000145:classification / Q000235:genetics*; D017753:Ecosystem; D049810:Genetic Speciation; D014644:Genetic Variation; D049750:Genome, Insect / Q000235:genetics*; D005838:Genotype; D006790:Host-Parasite Interactions; D015810:Linkage Disequilibrium; D012641:Selection, Genetic; D013045:Species Specificity; D014197:Trees / Q000469:parasitology*