title: Examining variation in the leaf mass per area of dominant species across two contrasting tropical gradients in light of community assembly.
abstract: Understanding variation in key functional traits across gradients in high diversity systems and the ecology of community changes along gradients in these systems is crucial in light of conservation and climate change. We examined inter- and intraspecific variation in leaf mass per area (LMA) of sun and shade leaves along a 3330-m elevation gradient in Peru, and in sun leaves across a forest-savanna vegetation gradient in Brazil. We also compared LMA variance ratios (T-statistics metrics) to null models to explore internal (i.e., abiotic) and environmental filtering on community structure along the gradients. Community-weighted LMA increased with decreasing forest cover in Brazil, likely due to increased light availability and water stress, and increased with elevation in Peru, consistent with the leaf economic spectrum strategy expected in colder, less productive environments. A very high species turnover was observed along both environmental gradients, and consequently, the first source of variation in LMA was species turnover. Variation in LMA at the genus or family levels was greater in Peru than in Brazil. Using dominant trees to examine possible filters on community assembly, we found that in Brazil, internal filtering was strongest in the forest, while environmental filtering was observed in the dry savanna. In Peru, internal filtering was observed along 80% of the gradient, perhaps due to variation in taxa or interspecific competition. Environmental filtering was observed at cloud zone edges and in lowlands, possibly due to water and nutrient availability, respectively. These results related to variation in LMA indicate that biodiversity in species rich tropical assemblages may be structured by differential niche-based processes. In the future, specific mechanisms generating these patterns of variation in leaf functional traits across tropical environmental gradients should be explored.
authors.affiliation: École Normale Supérieure 45, rue d'Ulm F75005 Paris France.
authors.forename: Margot
authors.initials: M
authors.lastname: Neyret
authors.affiliation: School of Geography and the Environment Environmental Change Institute University of Oxford South Parks Road Oxford OX1 3QYUK; Department of Biology Sonoma State University 1801 East Cotati Avenue Rohnert Park California 94928.
authors.forename: Lisa Patrick
authors.initials: LP
authors.lastname: Bentley
authors.affiliation: School of Geography and the Environment Environmental Change Institute University of Oxford South Parks Road Oxford OX1 3QY UK; Wageningen University 6708 PB Wageningen The Netherlands.
authors.forename: Imma
authors.initials: I
authors.lastname: Oliveras
authors.affiliation: Universidade do Estado de Mato Grosso BR 158 km 650 Nova Xavantina Mato Grosso Brazil.
authors.forename: Beatriz S
authors.initials: BS
authors.lastname: Marimon
authors.affiliation: Universidade do Estado de Mato Grosso BR 158 km 650 Nova Xavantina Mato Grosso Brazil.
authors.forename: Ben Hur
authors.initials: BH
authors.lastname: Marimon-Junior
authors.affiliation: Universidade do Estado de Mato Grosso BR 158 km 650 Nova Xavantina Mato Grosso Brazil.
authors.forename: Edmar
authors.initials: E
authors.lastname: Almeida de Oliveira
authors.affiliation: Universidade do Estado de Mato Grosso BR 158 km 650 Nova Xavantina Mato Grosso Brazil.
authors.forename: Fábio
authors.initials: F
authors.lastname: Barbosa Passos
authors.affiliation: Universidad San Antonio Abad de Cusco Av. de la Cultura, Nro. 733 Cusco Peru.
authors.forename: Rosa
authors.initials: R
authors.lastname: Castro Ccoscco
authors.affiliation: Universidade do Estado de Mato Grosso BR 158 km 650 Nova Xavantina Mato Grosso Brazil.
authors.forename: Josias
authors.initials: J
authors.lastname: Dos Santos
authors.affiliation: Universidade do Estado de Mato Grosso BR 158 km 650 Nova Xavantina Mato Grosso Brazil.
authors.forename: Simone
authors.initials: S
authors.lastname: Matias Reis
authors.affiliation: Universidade do Estado de Mato Grosso BR 158 km 650 Nova Xavantina Mato Grosso Brazil.
authors.forename: Paulo S
authors.initials: PS
authors.lastname: Morandi
authors.affiliation: Universidad San Antonio Abad de Cusco Av. de la Cultura, Nro. 733 Cusco Peru.
authors.forename: Gloria
authors.initials: G
authors.lastname: Rayme Paucar
authors.affiliation: Universidad San Antonio Abad de Cusco Av. de la Cultura, Nro. 733 Cusco Peru.
authors.forename: Arturo
authors.initials: A
authors.lastname: Robles Cáceres
authors.affiliation: Universidad San Antonio Abad de Cusco Av. de la Cultura, Nro. 733 Cusco Peru.
authors.forename: Yolvi
authors.initials: Y
authors.lastname: Valdez Tejeira
authors.affiliation: Universidad San Antonio Abad de Cusco Av. de la Cultura, Nro. 733 Cusco Peru.
authors.forename: Yovana
authors.initials: Y
authors.lastname: Yllanes Choque
authors.affiliation: School of Geography and the Environment Environmental Change Institute University of Oxford South Parks Road Oxford OX1 3QYUK; Sección Química Pontificia Universidad Católica del Perú Avenida Universitaria 1801 San Miguel Lima 32 Peru.
authors.forename: Norma
authors.initials: N
authors.lastname: Salinas
authors.affiliation: School of Geography and the Environment Environmental Change Institute University of Oxford South Parks Road Oxford OX1 3QY UK.
authors.forename: Alexander
authors.initials: A
authors.lastname: Shenkin
authors.affiliation: Department of Global Ecology Carnegie Institution for Science 260 Panama Street Stanford California 94305.
authors.forename: Gregory P
authors.initials: GP
authors.lastname: Asner
authors.affiliation: Instituto Multidisciplinario de Biología Vegetal (IMBIV) CONICET and FCEFyN Universidad Nacional de Córdoba Casilla de Correo 495 5000 Córdoba Argentina.
authors.forename: Sandra
authors.initials: S
authors.lastname: Díaz
authors.affiliation: Department of Ecology and Evolutionary Biology University of Arizona Tucson Arizona 85721; The Santa Fe Institute 1399 Hyde Park Rd Santa Fe New Mexico 87501.
authors.forename: Brian J
authors.initials: BJ
authors.lastname: Enquist
authors.affiliation: School of Geography and the Environment Environmental Change Institute University of Oxford South Parks Road Oxford OX1 3QY UK.
authors.forename: Yadvinder
authors.initials: Y
authors.lastname: Malhi
keywords: Community assembly; T‐statistics; environmental filtering; interspecific variation; intraspecific variation; leaf mass per area; limiting similarity; tropical forests