title: Inter and intra island introgression in a wolf spider radiation from the Galápagos, and its implications for parallel evolution.
abstract: Parallel radiations within island systems are often assumed to follow a simple scenario in which single colonization events are followed by in situ adaptive divergence. However, subsequent gene exchange after the initial colonization and during the divergence process might have important evolutionary impacts on species radiations. Gene exchange among ecologically similar species from different islands may lead to introgression of adaptive genetic variation and influence the parallel divergence process. In this study, we estimate levels of gene exchange within a wolf spider radiation of the genus Hogna Simon, 1885, from the Galápagos, wherein habitat specialization into 'high elevation' and 'coastal dry' species apparently evolved repeatedly on two islands. By using a multilocus approach we show that low levels of inter-island and relatively higher levels of intra island introgression shaped genetic variation in this species complex. Using these estimates, we demonstrate by means of a coalescence simulation that under these inter- and intra-island migration rates parallel evolution most likely evolves by introgression of adaptive alleles among islands, rather than through independent mutations despite the close genetic relationship of species within islands. As species phylogenies within radiations are frequently used to infer the divergence pattern, even relatively low levels of interspecific gene flow should not be neglected when interpreting parallel trait evolution.
authors.affiliation: Royal Belgian Institute of Natural Sciences, O.D. Taxonomy & Phylogeny, Vautierstraat 29, 1000 Brussels, Belgium; Terrestrial Ecology Unit, Biology Department, Ghent University, K.L. Ledeganckstraat 35, B-9000 Ghent, Belgium. Electronic address: charlotte.debusschere@gmail.com.
authors.forename: Charlotte
authors.initials: C
authors.lastname: De Busschere
authors.affiliation: Royal Belgian Institute of Natural Sciences, O.D. Taxonomy & Phylogeny, Vautierstraat 29, 1000 Brussels, Belgium; Terrestrial Ecology Unit, Biology Department, Ghent University, K.L. Ledeganckstraat 35, B-9000 Ghent, Belgium. Electronic address: steven.vanbelleghem@ugent.be.
authors.forename: Steven Marcel
authors.initials: SM
authors.lastname: Van Belleghem
authors.affiliation: Royal Belgian Institute of Natural Sciences, O.D. Taxonomy & Phylogeny, Vautierstraat 29, 1000 Brussels, Belgium; Terrestrial Ecology Unit, Biology Department, Ghent University, K.L. Ledeganckstraat 35, B-9000 Ghent, Belgium. Electronic address: Frederik.hendrickx@naturalsciences.be.
authors.forename: Frederik
authors.initials: F
authors.lastname: Hendrickx
mesh_terms: D000220:Adaptation, Biological / Q000235:genetics; D063147:Animal Distribution; D000818:Animals; D005075:Biological Evolution; D017753:Ecosystem; D004484:Ecuador; D051456:Gene Flow; D014644:Genetic Variation; D006239:Haplotypes; D062312:Islands; D008957:Models, Genetic; D010802:Phylogeny; D012641:Selection, Genetic; D017422:Sequence Analysis, DNA; D013112:Spiders / Q000145:classification*
keywords: Coalescence; Gene exchange; Hogna; Introgression; Migration; Multilocus