title: Comparative genome scan detects host-related divergent selection in the grasshopper Hesperotettix viridis.
abstract: In this study, we used a comparative genome scan to examine patterns of population differentiation with respect to host plant use in Hesperotettix viridis, a Nearctic oligophagous grasshopper locally specialized on various Asteraceae including Solidago, Gutierrezia, and Ericameria. We identified amplified fragment length polymorphism (AFLP) loci with significantly elevated F(ST) (outlier loci) in multiple different-host and same-host comparisons of populations while controlling for geographic distance. By comparing the number and identities of outlier loci in different-host vs. same-host comparisons, we found evidence of host plant-related divergent selection for some population comparisons (Solidago- vs. Gutierrezia-feeders), while other comparisons (Ericameria- vs. Gutierrezia-feeders) failed to demonstrate a strong role for host association in population differentiation. In comparisons of Solidago- vs. Gutierrezia-feeding populations, a relatively high number of outlier loci observed repeatedly in different-host comparisons (35% of all outliers and 2.7% of all 625 AFLP loci) indicated a significant role for host-related selection in contributing to overall genomic differentiation in this grasshopper. Mitochondrial DNA sequence data revealed a star-shaped phylogeny with no host- or geography-related structure, low nucleotide diversity, and high haplotype diversity, suggesting a recent population expansion. mtDNA data do not suggest a long period of isolation in separate glacial refugia but are instead more compatible with a single glacial refugium and more recent divergence in host use. Our study adds to research documenting heterogeneity in differentiation across the genome as a consequence of divergent natural selection, a phenomenon that may occur as part of the process of ecological speciation.
authors.affiliation: Division of Biology, Kansas State University, Manhattan, KS 66506, USA.
authors.forename: Jennifer L
authors.initials: JL
authors.lastname: Apple
authors.forename: Tony
authors.initials: T
authors.lastname: Grace
authors.forename: Anthony
authors.initials: A
authors.lastname: Joern
authors.forename: Paul
authors.initials: P
authors.lastname: St Amand
authors.forename: Samantha M
authors.initials: SM
authors.lastname: Wisely
mesh_terms: D054458:Amplified Fragment Length Polymorphism Analysis; D000818:Animals; D055028:Comparative Genomic Hybridization; D004272:DNA, Mitochondrial / Q000235:genetics; D005828:Genetics, Population; D005843:Geography; D006110:Grasshoppers / Q000235:genetics*; D058974:Phylogeography; D012641:Selection, Genetic; D017422:Sequence Analysis, DNA; D013045:Species Specificity
chemical_list: D004272:DNA, Mitochondrial