title: Persistent inter- and intraspecific gene exchange within a parallel radiation of caterpillar hunter beetles (Calosoma sp.) from the Galápagos.
abstract: When environmental gradients are repeated on different islands within an archipelago, similar selection pressures may act within each island, resulting in the repeated occurrence of ecologically similar species on each island. The evolution of ecotypes within such radiations may either result from dispersal, that is each ecotype evolved once and dispersed to different islands where it colonized its habitat, or through repeated and parallel speciation within each island. However, it remains poorly understood how gene flow during the divergence process may shape such patterns. In the Galápagos islands, three phenotypically similar species of the beetle genus Calosoma occur at higher elevations of different islands, while lowlands are occupied by a fourth species. By genotyping all major populations within this radiation for two nuclear and three mitochondrial gene fragments and seven microsatellite markers, we found strong support that the oldest divergence separates the highland species of the oldest island from the remaining species. Despite their morphological distinctness, highland species of the remaining islands were genetically closely related to the lowland population on each island and within the same magnitude as lowland populations sampled at different islands. Repeated evolution of highland ecotypes out of the lowland species appears the most likely scenario and estimates of geneflow rates revealed extensive admixture among ecotypes within islands, as well as between islands. These findings indicate that gene exchange among the different populations and species may have shaped the phylogenetic relationships and the repeated evolution of these ecotypes.
authors.affiliation: Royal Belgian Institute of Natural Sciences, Vautierstraat 29, Brussels, 1000, Belgium.|Terrestrial Ecology Unit (TEREC), Biology Department, Ghent University, K.L. Ledeganckstraat 35, Gent, 9000, Belgium.
authors.forename: Frederik
authors.initials: F
authors.lastname: Hendrickx
authors.affiliation: Royal Belgian Institute of Natural Sciences, Vautierstraat 29, Brussels, 1000, Belgium.|Evolutionary Ecology Group, Department of Biology, University of Antwerp, Groenenborgerlaan 171, Antwerp, 2020, Belgium.
authors.forename: Thierry
authors.initials: T
authors.lastname: Backeljau
authors.affiliation: Royal Belgian Institute of Natural Sciences, Vautierstraat 29, Brussels, 1000, Belgium.
authors.forename: Wouter
authors.initials: W
authors.lastname: Dekoninck
authors.affiliation: Royal Belgian Institute of Natural Sciences, Vautierstraat 29, Brussels, 1000, Belgium.|Terrestrial Ecology Unit (TEREC), Biology Department, Ghent University, K.L. Ledeganckstraat 35, Gent, 9000, Belgium.
authors.forename: Steven M
authors.initials: SM
authors.lastname: Van Belleghem
authors.affiliation: Terrestrial Ecology Unit (TEREC), Biology Department, Ghent University, K.L. Ledeganckstraat 35, Gent, 9000, Belgium.
authors.forename: Viki
authors.initials: V
authors.lastname: Vandomme
authors.affiliation: Royal Belgian Institute of Natural Sciences, Vautierstraat 29, Brussels, 1000, Belgium.|Terrestrial Ecology Unit (TEREC), Biology Department, Ghent University, K.L. Ledeganckstraat 35, Gent, 9000, Belgium.
authors.forename: Carl
authors.initials: C
authors.lastname: Vangestel
mesh_terms: D000818:Animals; D005075:Biological Evolution; D001517:Coleoptera / Q000235:genetics*; D004272:DNA, Mitochondrial / Q000235:genetics; D017753:Ecosystem; D060146:Ecotype; D004484:Ecuador; D051456:Gene Flow; D005787:Gene Frequency; D005828:Genetics, Population; D005838:Genotype; D062312:Islands; D018895:Microsatellite Repeats; D008969:Molecular Sequence Data; D010802:Phylogeny; D017422:Sequence Analysis, DNA
chemical_list: D004272:DNA, Mitochondrial
keywords: adaptive radiation; admixture; ecological speciation; introgression; islands; phylogeography