title: Carbohydrate reserves in the facilitator cushion plant Laretia acaulis suggest carbon limitation at high elevation and no negative effects of beneficiary plants.
abstract: The elevational range of the alpine cushion plant Laretia acaulis (Apiaceae) comprises a cold upper extreme and a dry lower extreme. For this species, we predict reduced growth and increased non-structural carbohydrate (NSC) concentrations (i.e. carbon sink limitation) at both elevational extremes. In a facilitative interaction, these cushions harbor other plant species (beneficiaries). Such interactions appear to reduce reproduction in other cushion species, but not in L. acaulis. However, vegetative effects may be more important in this long-lived species and may be stronger under marginal conditions. We studied growth and NSC concentrations in leaves and stems of L. acaulis collected from cushions along its full elevational range in the Andes of Central Chile. NSC concentrations were lowest and cushions were smaller and much less abundant at the highest elevation. At the lowest elevation, NSC concentrations and cushion sizes were similar to those of intermediate elevations but cushions were somewhat less abundant. NSC concentrations and growth did not change with beneficiary cover at any elevation. Lower NSC concentrations at the upper extreme contradict the sink-limitation hypothesis and may indicate that a lack of warmth is not limiting growth at high-elevation. At the lower extreme, carbon gain and growth do not appear more limiting than at intermediate elevations. The lower population density at both extremes suggests that the regeneration niche exerts important limitations to this species' distribution. The lack of an effect of beneficiaries on reproduction and vegetative performance suggests that the interaction between L. acaulis and its beneficiaries is probably commensalistic.
authors.affiliation: Departamento de Botánica, Facultad de Ciencias Naturales y Oceanográficas, Universidad de Concepción, Barrio Universitario s/n, Casilla 160-C, Concepción, Chile. mc.garcia.lino@gmail.com.|Instituto de Ecología y Biodiversidad (IEB), Las Palmeras 3425 Ñuñoa, Casilla 653, Santiago, Chile. mc.garcia.lino@gmail.com.|Herbario Nacional de Bolivia, Universidad Mayor de San Andrés, Calle 27 Cota Cota s/n, Casilla 10077, La Paz, Bolivia. mc.garcia.lino@gmail.com.
authors.forename: Mary Carolina
authors.initials: MC
authors.lastname: García Lino
authors.affiliation: Departamento de Botánica, Facultad de Ciencias Naturales y Oceanográficas, Universidad de Concepción, Barrio Universitario s/n, Casilla 160-C, Concepción, Chile.|Instituto de Ecología y Biodiversidad (IEB), Las Palmeras 3425 Ñuñoa, Casilla 653, Santiago, Chile.
authors.forename: Lohengrin A
authors.initials: LA
authors.lastname: Cavieres
authors.affiliation: Functional Ecology, Institute of Biology and Environmental Sciences, Carl-von-Ossietzky University, Carl-von-Ossietzky-Str. 9-11, 26111, Oldenburg, Germany.
authors.forename: Gerhard
authors.initials: G
authors.lastname: Zotz
authors.affiliation: Ecological Plant Geography, Faculty of Geography, University of Marburg, Deutschhausstr. 10, 35032, Marburg, Germany.
authors.forename: Maaike Y
authors.initials: MY
authors.lastname: Bader
mesh_terms: D000531:Altitude; D019661:Apiaceae; D002241:Carbohydrates; D002244:Carbon; D010944:Plants
chemical_list: D002241:Carbohydrates; D002244:Carbon
keywords: Facilitation; Fitness; Foundation species; NSC; Plant–plant interactions