title: Alteration of sexual reproduction and genetic diversity in the kelp species Laminaria digitata at the southern limit of its range.
abstract: Adaptation to marginal habitats at species range-limits has often been associated with parthenogenetic reproduction in terrestrial animals and plants. Laboratory observations have shown that brown algae exhibit a high propensity for parthenogenesis by various mechanisms. The kelp Laminaria digitata is an important component of the ecosystem in Northern European rocky intertidal habitats. We studied four L. digitata populations for the effects of marginality on genetic diversity and sexual reproduction. Two populations were marginal: One (Locquirec, in Northern Brittany) was well within the geographic range, but was genetically isolated from other populations by large stretches of sandy beaches. Another population was at the range limits of the species (Quiberon, in Southern Brittany) and was exposed to much higher seasonal temperature changes. Microsatellite analyses confirmed that these populations showed decreased genetic and allelic diversity, consistent with marginality and genetic isolation. Sporophytes from both marginal populations showed greatly diminished spore-production compared to central populations, but only the southern-limit population (Quiberon) showed a high propensity for producing unreduced (2N) spores. Unreduced 2N spores formed phenotypically normal gametophytes with nuclear area consistent with ≥2N DNA contents, and microsatellite studies suggested these were produced at least in part by automixis. However, despite this being the dominant path of spore production in Quiberon sporophyte individuals, the genetic evidence indicated the population was maintained mostly by sexual reproduction. Thus, although spore production and development showed the expected tendency of geographical parthenogenesis in marginal populations, this appeared to be a consequence of maladaptation, rather than an adaptation to, life in a marginal habitat.
authors.affiliation: Departamento de Ecología, Facultad de Ciencias Biológicas, Pontificia Universidad Católica de Chile, Santiago, Chile; Sorbonne Universités, UPMC Univ. Paris 06, UMR 7144, Station Biologique de Roscoff, Roscoff, France; CNRS, UMR 7144, Station Biologique de Roscoff, Place Georges Teissier, Roscoff, France; Center of Applied Ecology & Sustainability, Facultad de Ciencias Biológicas, Pontificia Universidad Católica de Chile, Santiago, Chile.
authors.forename: Luz Valeria
authors.initials: LV
authors.lastname: Oppliger
authors.affiliation: Departamento de Ecología, Facultad de Ciencias Biológicas, Pontificia Universidad Católica de Chile, Santiago, Chile; Instituto Milenio de Oceanografía (IMO), Pontificia Universidad Católica de Chile, Santiago, Chile.
authors.forename: Peter
authors.initials: P
authors.lastname: von Dassow
authors.affiliation: Sorbonne Universités, UPMC Univ. Paris 06, UMR 7144, Station Biologique de Roscoff, Roscoff, France; CNRS, UMR 7144, Station Biologique de Roscoff, Place Georges Teissier, Roscoff, France.
authors.forename: Sarah
authors.initials: S
authors.lastname: Bouchemousse
authors.affiliation: Sorbonne Universités, UPMC Univ. Paris 06, UMR 7144, Station Biologique de Roscoff, Roscoff, France; CNRS, UMR 7144, Station Biologique de Roscoff, Place Georges Teissier, Roscoff, France; Institut de Systématique, Evolution, Biodiversité, UMR 7205, Muséum national d'Histoire naturelle, Paris, France.
authors.forename: Marine
authors.initials: M
authors.lastname: Robuchon
authors.affiliation: Sorbonne Universités, UPMC Univ. Paris 06, UMR 7144, Station Biologique de Roscoff, Roscoff, France; CNRS, UMR 7144, Station Biologique de Roscoff, Place Georges Teissier, Roscoff, France.
authors.forename: Myriam
authors.initials: M
authors.lastname: Valero
authors.affiliation: Departamento de Ecología, Facultad de Ciencias Biológicas, Pontificia Universidad Católica de Chile, Santiago, Chile; Center of Applied Ecology & Sustainability, Facultad de Ciencias Biológicas, Pontificia Universidad Católica de Chile, Santiago, Chile.
authors.forename: Juan A
authors.initials: JA
authors.lastname: Correa
authors.affiliation: Sorbonne Universités, UPMC Univ. Paris 06, UMR 7144, Station Biologique de Roscoff, Roscoff, France; CNRS, UMR 7144, Station Biologique de Roscoff, Place Georges Teissier, Roscoff, France.
authors.forename: Stéphane
authors.initials: S
authors.lastname: Mauger
authors.affiliation: Sorbonne Universités, UPMC Univ. Paris 06, UMR 7144, Station Biologique de Roscoff, Roscoff, France; CNRS, UMR 7144, Station Biologique de Roscoff, Place Georges Teissier, Roscoff, France.
authors.forename: Christophe
authors.initials: C
authors.lastname: Destombe
mesh_terms: D017753:Ecosystem; D014644:Genetic Variation; D005843:Geography; D007795:Laminaria / Q000235:genetics* / Q000502:physiology; D018895:Microsatellite Repeats; D011003:Ploidies; D012098:Reproduction / Q000502:physiology; D060047:Reproductive Isolation; D012623:Seawater; D013696:Temperature