title: Genome-wide patterns of divergence and gene flow across a butterfly radiation.
abstract: The Heliconius butterflies are a diverse recent radiation comprising multiple levels of divergence with ongoing gene flow between species. The recently sequenced genome of Heliconius melpomene allowed us to investigate the genomic evolution of this group using dense RAD marker sequencing. Phylogenetic analysis of 54 individuals robustly supported reciprocal monophyly of H. melpomene and Heliconius cydno and refuted previous phylogenetic hypotheses that H. melpomene may be paraphylectic with respect to H. cydno. Heliconius timareta also formed a monophyletic clade closely related but distinct from H. cydno with Heliconius heurippa falling within this clade. We find evidence for genetic admixture between sympatric populations of the sister clades H. melpomene and H. cydno/timareta, particularly between H. cydno and H. melpomene from Central America and between H. timareta and H. melpomene from the eastern slopes of the Andes. Between races, divergence is primarily explained by isolation by distance and there is no detectable genetic population structure between parapatric races, suggesting that hybrid zones between races are not zones of secondary contact. Our results also support previous findings that colour pattern loci are shared between populations and species with similar colour pattern elements. Furthermore, this pattern is almost unique to these genomic regions, with only a very small number of other loci showing significant similarity between populations and species with similar colour patterns.
authors.affiliation: Department of Zoology, University of Cambridge, Cambridge, UK. njn27@cam.ac.uk
authors.forename: Nicola J
authors.initials: NJ
authors.lastname: Nadeau
authors.forename: Simon H
authors.initials: SH
authors.lastname: Martin
authors.forename: Krzysztof M
authors.initials: KM
authors.lastname: Kozak
authors.forename: Camilo
authors.initials: C
authors.lastname: Salazar
authors.forename: Kanchon K
authors.initials: KK
authors.lastname: Dasmahapatra
authors.forename: John W
authors.initials: JW
authors.lastname: Davey
authors.forename: Simon W
authors.initials: SW
authors.lastname: Baxter
authors.forename: Mark L
authors.initials: ML
authors.lastname: Blaxter
authors.forename: James
authors.initials: J
authors.lastname: Mallet
authors.forename: Chris D
authors.initials: CD
authors.lastname: Jiggins
mesh_terms: D000818:Animals; D002080:Butterflies / Q000145:classification / Q000235:genetics*; D051456:Gene Flow; D017344:Genes, Insect; D056426:Genetic Loci; D049810:Genetic Speciation; D005828:Genetics, Population; D060005:Genotyping Techniques; D005843:Geography; D016013:Likelihood Functions; D010802:Phylogeny; D010858:Pigmentation; D020641:Polymorphism, Single Nucleotide; D017422:Sequence Analysis, DNA; D013020:South America; D061350:Sympatry