title: PHENOTYPIC DIFFERENTIATION AT SOUTHERN LIMIT BORDERS: THE CASE STUDY OF TWO FUCOID MACROALGAL SPECIES WITH DIFFERENT LIFE-HISTORY TRAITS1.
abstract: Marginal populations are often geographically isolated, smaller, and more fragmented than central populations and may frequently have to face suboptimal local environmental conditions. Persistence of these populations frequently involves the development of adaptive traits at phenotypic and genetic levels. We compared population structure and demographic variables in two fucoid macroalgal species contrasting in patterns of genetic diversity and phenotypic plasticity at their southern distribution limit with a more central location. Models were Ascophyllum nodosum (L.) Le Jol. (whose extreme longevity and generation overlap may buffer genetic loss by drift) and Fucus serratus L. (with low genetic diversity at southern margins). At edge locations, both species exhibited trends in life-history traits compatible with population persistence but by using different mechanisms. Marginal populations of A. nodosum had higher reproductive output in spite of similar mortality rates at all life stages, making edge populations denser and with smaller individuals. In F. serratus, rather than demographic changes, marginal populations differed in habitat, occurring restricted to a narrower vertical habitat range. We conclude that persistence of both A. nodosum and F. serratus at the southern-edge locations depends on different strategies. Marginal population persistence in A. nodosum relies on a differentiation in life-history traits, whereas F. serratus, putatively poorer in evolvability potential, is restricted to a narrower vertical range at border locations. These results contribute to the general understanding of mechanisms that lead to population persistence at distributional limits and to predict population resilience under a scenario of environmental change.
authors.affiliation: Centre of Marine and Environmental Research, University of Porto (CIMAR-Porto), Rua dos Bragas, 289, 4050-123 Porto, PortugalCentre of Marine Sciences, University of Algarve (CIMAR-Algarve), Campus of Gambelas, 8005-139 Faro, Portugal Centre of Marine and Environmental Research, University of Porto (CIMAR-Porto), Rua dos Bragas, 289, 4050-123 Porto, Portugal Department of Biology, Faculty of Sciences, University of Porto, Rua do Campo Alegre, s/n, 4050 Porto, PortugalDepartment of Marine Ecology, University of Gothenburg, Box 461, 40530 Göteborg, Sweden.
authors.forename: Rita
authors.initials: R
authors.lastname: Araújo
authors.affiliation: Centre of Marine and Environmental Research, University of Porto (CIMAR-Porto), Rua dos Bragas, 289, 4050-123 Porto, PortugalCentre of Marine Sciences, University of Algarve (CIMAR-Algarve), Campus of Gambelas, 8005-139 Faro, Portugal Centre of Marine and Environmental Research, University of Porto (CIMAR-Porto), Rua dos Bragas, 289, 4050-123 Porto, Portugal Department of Biology, Faculty of Sciences, University of Porto, Rua do Campo Alegre, s/n, 4050 Porto, PortugalDepartment of Marine Ecology, University of Gothenburg, Box 461, 40530 Göteborg, Sweden.
authors.forename: Ester A
authors.initials: EA
authors.lastname: Serrão
authors.affiliation: Centre of Marine and Environmental Research, University of Porto (CIMAR-Porto), Rua dos Bragas, 289, 4050-123 Porto, PortugalCentre of Marine Sciences, University of Algarve (CIMAR-Algarve), Campus of Gambelas, 8005-139 Faro, Portugal Centre of Marine and Environmental Research, University of Porto (CIMAR-Porto), Rua dos Bragas, 289, 4050-123 Porto, Portugal Department of Biology, Faculty of Sciences, University of Porto, Rua do Campo Alegre, s/n, 4050 Porto, PortugalDepartment of Marine Ecology, University of Gothenburg, Box 461, 40530 Göteborg, Sweden.
authors.forename: Isabel
authors.initials: I
authors.lastname: Sousa-Pinto
authors.affiliation: Centre of Marine and Environmental Research, University of Porto (CIMAR-Porto), Rua dos Bragas, 289, 4050-123 Porto, PortugalCentre of Marine Sciences, University of Algarve (CIMAR-Algarve), Campus of Gambelas, 8005-139 Faro, Portugal Centre of Marine and Environmental Research, University of Porto (CIMAR-Porto), Rua dos Bragas, 289, 4050-123 Porto, Portugal Department of Biology, Faculty of Sciences, University of Porto, Rua do Campo Alegre, s/n, 4050 Porto, PortugalDepartment of Marine Ecology, University of Gothenburg, Box 461, 40530 Göteborg, Sweden.
authors.forename: Per
authors.initials: P
authors.lastname: Åberg
keywords: Ascophyllum nodosum; Fucus serratus; geographic distribution limits; marginal populations; phenotypic differentiation; population persistence