title: THE LESSONIA NIGRESCENS SPECIES COMPLEX (LAMINARIALES, PHAEOPHYCEAE) SHOWS STRICT PARAPATRY AND COMPLETE REPRODUCTIVE ISOLATION IN A SECONDARY CONTACT ZONE(1).
abstract: During secondary contact between phylogenetically closely related species (sibling species) having diverged in allopatry, the maintenance of species integrity depends on intrinsic and extrinsic reproductive barriers. In kelps (Phaeophyceae), the observations of hybrids in laboratory conditions suggest that reproductive isolation is incomplete. However, not all interspecific crosses are successful, and very few hybrids have been observed in nature, despite the co-occurrence of many kelp species in sympatry. This suggests that there are reproductive barriers that maintain species integrity. In this study, we characterized the fine genetic structure of a secondary contact zone to clarify the extent of reproductive isolation between two sister species. In Lessonia nigrescens Bory (Laminariales, Phaeophyta) species complex, two cryptic species have been recently found out from gene phylogenies, and-waiting for a formal taxonomic description-we used their geographic distribution to name them (northern and southern species). We studied 12 populations, distributed along 50 km of coastline, and employed two molecular approaches, assigning individuals to phylogenetic species according to a diagnostic mitochondrial marker (351 individuals analyzed) and quantifying interspecific gene flow with four microsatellite markers (248 individuals analyzed). No hybridization or introgression was revealed, indicating complete reproductive isolation in natural conditions. Unexpectedly, our study demonstrated that the two species were strictly segregated in space. This absence of co-occurrence along the contact zone can partially explain the lack of hybridization, raising new interesting questions as to the mechanisms that limit sympatry at small spatial scales.
authors.affiliation: Center for Advanced Studies in Ecology and Biodiversity, Facultad de Ciencias Biológicas, "LIA DIAMS", Pontificia Universidad Católica de Chile, Post-code 6513677, Santiago, Chile UPMC Univ. Paris VI, UMR 7144, Equipe "BEDIM", LIA "DIAMS", Station Biologique de Roscoff, 29682 Roscoff, France CNRS, UMR 7144, Station Biologique de Roscoff, Place Georges Teissier, 29682 Roscoff, France Facultad de Ciencias del Mar, Universidad Católica del Norte & CEAZA, Larrondo 1281, Coquimbo, ChileCenter for Advanced Studies in Ecology and Biodiversity, Facultad de Ciencias Biológicas, "LIA DIAMS", Pontificia Universidad Católica de Chile, Post-code 6513677, Santiago, Chile UPMC Univ. Paris VI, UMR 7144, Equipe "BEDIM", LIA "DIAMS", Station Biologique de Roscoff, 29682 Roscoff, France CNRS, UMR 7144, Station Biologique de Roscoff, Place Georges Teissier, 29682 Roscoff, France.
authors.forename: Florence
authors.initials: F
authors.lastname: Tellier
authors.affiliation: Center for Advanced Studies in Ecology and Biodiversity, Facultad de Ciencias Biológicas, "LIA DIAMS", Pontificia Universidad Católica de Chile, Post-code 6513677, Santiago, Chile UPMC Univ. Paris VI, UMR 7144, Equipe "BEDIM", LIA "DIAMS", Station Biologique de Roscoff, 29682 Roscoff, France CNRS, UMR 7144, Station Biologique de Roscoff, Place Georges Teissier, 29682 Roscoff, France Facultad de Ciencias del Mar, Universidad Católica del Norte & CEAZA, Larrondo 1281, Coquimbo, ChileCenter for Advanced Studies in Ecology and Biodiversity, Facultad de Ciencias Biológicas, "LIA DIAMS", Pontificia Universidad Católica de Chile, Post-code 6513677, Santiago, Chile UPMC Univ. Paris VI, UMR 7144, Equipe "BEDIM", LIA "DIAMS", Station Biologique de Roscoff, 29682 Roscoff, France CNRS, UMR 7144, Station Biologique de Roscoff, Place Georges Teissier, 29682 Roscoff, France.
authors.forename: Javier
authors.initials: J
authors.lastname: Tapia
authors.affiliation: Center for Advanced Studies in Ecology and Biodiversity, Facultad de Ciencias Biológicas, "LIA DIAMS", Pontificia Universidad Católica de Chile, Post-code 6513677, Santiago, Chile UPMC Univ. Paris VI, UMR 7144, Equipe "BEDIM", LIA "DIAMS", Station Biologique de Roscoff, 29682 Roscoff, France CNRS, UMR 7144, Station Biologique de Roscoff, Place Georges Teissier, 29682 Roscoff, France Facultad de Ciencias del Mar, Universidad Católica del Norte & CEAZA, Larrondo 1281, Coquimbo, ChileCenter for Advanced Studies in Ecology and Biodiversity, Facultad de Ciencias Biológicas, "LIA DIAMS", Pontificia Universidad Católica de Chile, Post-code 6513677, Santiago, Chile UPMC Univ. Paris VI, UMR 7144, Equipe "BEDIM", LIA "DIAMS", Station Biologique de Roscoff, 29682 Roscoff, France CNRS, UMR 7144, Station Biologique de Roscoff, Place Georges Teissier, 29682 Roscoff, France.
authors.forename: Sylvain
authors.initials: S
authors.lastname: Faugeron
authors.affiliation: Center for Advanced Studies in Ecology and Biodiversity, Facultad de Ciencias Biológicas, "LIA DIAMS", Pontificia Universidad Católica de Chile, Post-code 6513677, Santiago, Chile UPMC Univ. Paris VI, UMR 7144, Equipe "BEDIM", LIA "DIAMS", Station Biologique de Roscoff, 29682 Roscoff, France CNRS, UMR 7144, Station Biologique de Roscoff, Place Georges Teissier, 29682 Roscoff, France Facultad de Ciencias del Mar, Universidad Católica del Norte & CEAZA, Larrondo 1281, Coquimbo, ChileCenter for Advanced Studies in Ecology and Biodiversity, Facultad de Ciencias Biológicas, "LIA DIAMS", Pontificia Universidad Católica de Chile, Post-code 6513677, Santiago, Chile UPMC Univ. Paris VI, UMR 7144, Equipe "BEDIM", LIA "DIAMS", Station Biologique de Roscoff, 29682 Roscoff, France CNRS, UMR 7144, Station Biologique de Roscoff, Place Georges Teissier, 29682 Roscoff, France.
authors.forename: Christophe
authors.initials: C
authors.lastname: Destombe
authors.affiliation: Center for Advanced Studies in Ecology and Biodiversity, Facultad de Ciencias Biológicas, "LIA DIAMS", Pontificia Universidad Católica de Chile, Post-code 6513677, Santiago, Chile UPMC Univ. Paris VI, UMR 7144, Equipe "BEDIM", LIA "DIAMS", Station Biologique de Roscoff, 29682 Roscoff, France CNRS, UMR 7144, Station Biologique de Roscoff, Place Georges Teissier, 29682 Roscoff, France Facultad de Ciencias del Mar, Universidad Católica del Norte & CEAZA, Larrondo 1281, Coquimbo, ChileCenter for Advanced Studies in Ecology and Biodiversity, Facultad de Ciencias Biológicas, "LIA DIAMS", Pontificia Universidad Católica de Chile, Post-code 6513677, Santiago, Chile UPMC Univ. Paris VI, UMR 7144, Equipe "BEDIM", LIA "DIAMS", Station Biologique de Roscoff, 29682 Roscoff, France CNRS, UMR 7144, Station Biologique de Roscoff, Place Georges Teissier, 29682 Roscoff, France.
authors.forename: Myriam
authors.initials: M
authors.lastname: Valero
keywords: biological species concept; gene flow; hybridization; kelp; microsatellite; parapatry; reproductive isolation; secondary contact