title: Genomic islands of divergence are not affected by geography of speciation in sunflowers.
abstract: Genomic studies of speciation often report the presence of highly differentiated genomic regions interspersed within a milieu of weakly diverged loci. The formation of these speciation islands is generally attributed to reduced inter-population gene flow near loci under divergent selection, but few studies have critically evaluated this hypothesis. Here, we report on transcriptome scans among four recently diverged pairs of sunflower (Helianthus) species that vary in the geographical context of speciation. We find that genetic divergence is lower in sympatric and parapatric comparisons, consistent with a role for gene flow in eroding neutral differences. However, genomic islands of divergence are numerous and small in all comparisons, and contrary to expectations, island number and size are not significantly affected by levels of interspecific gene flow. Rather, island formation is strongly associated with reduced recombination rates. Overall, our results indicate that the functional architecture of genomes plays a larger role in shaping genomic divergence than does the geography of speciation.
authors: Biodiversity Research Centre and Department of Botany, University of British Columbia, Vancouver, British Columbia, Canada V6T 1Z4.
authors: S
authors: S
authors: Renaut
authors: C J
authors: CJ
authors: Grassa
authors: S
authors: S
authors: Yeaman
authors: B T
authors: BT
authors: Moyers
authors: Z
authors: Z
authors: Lai
authors: N C
authors: NC
authors: Kane
authors: J E
authors: JE
authors: Bowers
authors: J M
authors: JM
authors: Burke
authors: L H
authors: LH
authors: Rieseberg
mesh_terms: D019943:Amino Acid Substitution / Q000235:genetics; D002874:Chromosome Mapping; D019143:Evolution, Molecular; D049810:Genetic Speciation; D014644:Genetic Variation; D018745:Genome, Plant / Q000235:genetics; D044404:Genomic Islands / Q000235:genetics*; D005843:Geography; D006368:Helianthus / Q000235:genetics*; D010802:Phylogeny; D020641:Polymorphism, Single Nucleotide / Q000235:genetics; D011995:Recombination, Genetic / Q000235:genetics; D012641:Selection, Genetic; D013045:Species Specificity; D059467:Transcriptome / Q000235:genetics
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