Functional traits determine plant co-occurrence more than environment or evolutionary relatedness in global drylands.
Plant-plant interactions are driven by environmental conditions, evolutionary relationships (ER) and the functional traits of the plants involved. However, studies addressing the relative importance of these drivers are rare, but crucial to improve our predictions of the effects of plant-plant interactions on plant communities and of how they respond to differing environmental conditions. To analyze the relative importance of -and interrelationships among- these factors as drivers of plant-plant interactions, we analyzed perennial plant co-occurrence at 106 dryland plant communities established across rainfall gradients in nine countries. We used structural equation modeling to disentangle the relationships between environmental conditions (aridity and soil fertility), functional traits extracted from the literature, and ER, and to assess their relative importance as drivers of the 929 pairwise plant-plant co-occurrence levels measured. Functional traits, specifically facilitated plants' height and nurse growth form, were of primary importance, and modulated the effect of the environment and ER on plant-plant interactions. Environmental conditions and ER were important mainly for those interactions involving woody and graminoid nurses, respectively. The relative importance of different plant-plant interaction drivers (ER, functional traits, and the environment) varied depending on the region considered, illustrating the difficulty of predicting the outcome of plant-plant interactions at broader spatial scales. In our global-scale study on drylands, plant-plant interactions were more strongly related to functional traits of the species involved than to the environmental variables considered. Thus, moving to a trait-based facilitation/competition approach help to predict that: 1) positive plant-plant interactions are more likely to occur for taller facilitated species in drylands, and 2) plant-plant interactions within woody-dominated ecosystems might be more sensitive to changing environmental conditions than those within grasslands. By providing insights on which species are likely to better perform beneath a given neighbour, our results will also help to succeed in restoration practices involving the use of nurse plants.
Área de Biodiversidad y Conservación, Departamento de Biología y Geología, Escuela Superior de Ciencias Experimentales y Tecnología, Universidad Rey Juan Carlos, Calle Tulipán S/N, 28933 Móstoles, Spain.
Santiago
S
Soliveres
Área de Biodiversidad y Conservación, Departamento de Biología y Geología, Escuela Superior de Ciencias Experimentales y Tecnología, Universidad Rey Juan Carlos, Calle Tulipán S/N, 28933 Móstoles, Spain.
Fernando T
FT
Maestre
School of Forestry, Northern Arizona University, 200 East Pine Knoll Drive, AZ 86011, Flagstaff, USA.
Matthew A
MA
Bowker
Centro de Ecologia Funcional. Departamento de Ciências da Vida. Universidade de Coimbra. 3001-455. Coimbra, Portugal.
Rubén
R
Torices
Área de Biodiversidad y Conservación, Departamento de Biología y Geología, Escuela Superior de Ciencias Experimentales y Tecnología, Universidad Rey Juan Carlos, Calle Tulipán S/N, 28933 Móstoles, Spain. ; Departamento de Ingeniería Forestal, Escuela Técnica Superior de Ingeniería Agronómica y de Montes. Universidad de Córdoba. Edificio Leonardo da Vinci, 1 planta. Campus de Rabanales. Ctra N-IV km 396. C.P. 14071, Córdoba, Spain.
José L
JL
Quero
Área de Biodiversidad y Conservación, Departamento de Biología y Geología, Escuela Superior de Ciencias Experimentales y Tecnología, Universidad Rey Juan Carlos, Calle Tulipán S/N, 28933 Móstoles, Spain. ; Departamento de Ingeniería y Morfología del Terreno, Escuela Técnica Superior de Ingenieros de Caminos, Canales y Puertos, Universidad Politécnica de Madrid, Calle Profesor Aranguren S/N, 28040 Madrid, Spain.
Miguel
M
García-Gómez
Instituto de Ecología, Universidad Técnica Particular de Loja, San Cayetano Alto, Marcelino Champagnat, Loja, Ecuador.
Omar
O
Cabrera
Departamento de Biología, Universidad de La Serena, Casilla 599.
Alex
A
Cea
Instituto Regional de Ciencias Ambientales (IRECA) Universidad Nacional San Agustín de Arequipa. Arequipa, Perú.
Daniel
D
Coaguila
School of Biological, Earth and Environmental Sciences, University of New South Wales, Sydney, New South Wales 2052, Australia.
David J
DJ
Eldridge
Instituto de Ecología, Universidad Técnica Particular de Loja, San Cayetano Alto, Marcelino Champagnat, Loja, Ecuador.
Carlos I
CI
Espinosa
School of Biological, Earth and Environmental Sciences, University of New South Wales, Sydney, New South Wales 2052, Australia.
Frank
F
Hemmings
Université du Québec à Montréal Pavillon des sciences biologiques Département des sciences biologiques 141 Président-Kennedy Montréal, Québec H2X 3Y5, Canada.
Jorge J
JJ
Monerris
Department of Agronomy and Soil Science, School of Environmental and Rural Science, University of New England, Armidale, New South Wales 2351, Australia.
Matthew
M
Tighe
Área de Biodiversidad y Conservación, Departamento de Biología y Geología, Escuela Superior de Ciencias Experimentales y Tecnología, Universidad Rey Juan Carlos, Calle Tulipán S/N, 28933 Móstoles, Spain. ; Departamento de Sistemas Físicos, Químicos y Naturales, Universidad Pablo de Olavide, Carretera de Utrera kilómetro 1, 41013 Sevilla, Spain.
Manuel
M
Delgado-Baquerizo
Área de Biodiversidad y Conservación, Departamento de Biología y Geología, Escuela Superior de Ciencias Experimentales y Tecnología, Universidad Rey Juan Carlos, Calle Tulipán S/N, 28933 Móstoles, Spain.
Cristina
C
Escolar
Department of Biology, Colorado State University, Fort Collins, Colorado 80523, USA.
Pablo
P
García-Palacios
Área de Biodiversidad y Conservación, Departamento de Biología y Geología, Escuela Superior de Ciencias Experimentales y Tecnología, Universidad Rey Juan Carlos, Calle Tulipán S/N, 28933 Móstoles, Spain.
Beatriz
B
Gozalo
Área de Biodiversidad y Conservación, Departamento de Biología y Geología, Escuela Superior de Ciencias Experimentales y Tecnología, Universidad Rey Juan Carlos, Calle Tulipán S/N, 28933 Móstoles, Spain.
Victoria
V
Ochoa
Laboratorio de Biogeoquímica, Centro de Agroecología Tropical, Universidad Experimental Simón Rodríguez, Apdo 47925, Caracas, Venezuela.
Julio
J
Blones
Direction Régionale des Eaux et Forêts et de la Lutte Contre la Désertification du Rif, Avenue Mohamed 5, Boîte Postale 722, 93000 Tétouan, Morocco.
Mchich
M
Derak
Université de Sfax, Faculté des Sciences, Unité de Recherche Plant Diversity and Ecosystems in Arid Environments, Route de Sokra, km 3.5, Boîte Postale 802, 3018, Sfax, Tunisia.
Wahida
W
Ghiloufi
Departamento de Biología, Universidad de La Serena, Casilla 599. ; Centro de Estudios Avanzados en Zonas Áridas (CEAZA), La Serena, Chile. ; Instituto de Ecología y Biodiversidad (IEB), Santiago, Chile.
Julio R
JR
Gutiérrez
Laboratorio de Biogeoquímica, Centro de Agroecología Tropical, Universidad Experimental Simón Rodríguez, Apdo 47925, Caracas, Venezuela.
Rosa M
RM
Hernández
Université de Sfax, Faculté des Sciences, Unité de Recherche Plant Diversity and Ecosystems in Arid Environments, Route de Sokra, km 3.5, Boîte Postale 802, 3018, Sfax, Tunisia.
Zouhaier
Z
Noumi
aridity; biotic interactions; competition; facilitation; phylogenetic distance; plant functional traits; semi-arid; soil fertility