title: Functional trait space and the latitudinal diversity gradient.
abstract: The processes causing the latitudinal gradient in species richness remain elusive. Ecological theories for the origin of biodiversity gradients, such as competitive exclusion, neutral dynamics, and environmental filtering, make predictions for how functional diversity should vary at the alpha (within local assemblages), beta (among assemblages), and gamma (regional pool) scales. We test these predictions by quantifying hypervolumes constructed from functional traits representing major axes of plant strategy variation (specific leaf area, plant height, and seed mass) in tree assemblages spanning the temperate and tropical New World. Alpha-scale trait volume decreases with absolute latitude and is often lower than sampling expectation, consistent with environmental filtering theory. Beta-scale overlap decays with geographic distance fastest in the temperate zone, again consistent with environmental filtering theory. In contrast, gamma-scale trait space shows a hump-shaped relationship with absolute latitude, consistent with no theory. Furthermore, the overall temperate trait hypervolume was larger than the overall tropical hypervolume, indicating that the temperate zone permits a wider range of trait combinations or that niche packing is stronger in the tropical zone. Although there are limitations in the data, our analyses suggest that multiple processes have shaped trait diversity in trees, reflecting no consistent support for any one theory.
authors.affiliation: Sustainability Solutions Initiative and.
authors.forename: Christine
authors.initials: C
authors.lastname: Lamanna
authors.affiliation: Department of Ecology and Evolutionary Biology, University of Arizona, Tucson, AZ 85721; Center for Macroecology, Evolution, and Climate, Copenhagen University, 2100 Copenhagen, Denmark;
authors.forename: Benjamin
authors.initials: B
authors.lastname: Blonder
authors.affiliation: Centre d'Ecologie Fonctionelle et Evolutive, Unité Mixte de Recherche 5175, Centre National de la Recherche Scientifique-Université de Montpellier-Université Paul-Valéry Montpellier-École Pratique des Hautes Études, 34293 Montpellier, France; cyrille.violle@cefe.cnrs.fr.
authors.forename: Cyrille
authors.initials: C
authors.lastname: Violle
authors.affiliation: Department of Biology, University of Maryland, College Park, MD 20742;
authors.forename: Nathan J B
authors.initials: NJ
authors.lastname: Kraft
authors.affiliation: Section for Ecoinformatics and Biodiversity, Department of Bioscience and Center for Massive Data Algorithmics, Department of Computer Science, Aarhus University, DK-8000 Aarhus, Denmark;
authors.forename: Brody
authors.initials: B
authors.lastname: Sandel
authors.affiliation: Center for Theoretical Study, Charles University in Prague and Academy of Sciences of the Czech Republic, 110 00 Praha, Czech Republic;
authors.forename: Irena
authors.initials: I
authors.lastname: Šímová
authors.affiliation: Department of Ecology and Evolutionary Biology, University of Arizona, Tucson, AZ 85721; iPlant Collaborative, Tucson, AZ 85721;
authors.forename: John C
authors.initials: JC
authors.lastname: Donoghue
authors.affiliation: Section for Ecoinformatics and Biodiversity, Department of Bioscience and.
authors.forename: Jens-Christian
authors.initials: JC
authors.lastname: Svenning
authors.affiliation: Sustainability Solutions Initiative and School of Biology and Ecology, University of Maine, Orono, ME 04469;
authors.forename: Brian J
authors.initials: BJ
authors.lastname: McGill
authors.affiliation: Department of Ecology and Evolutionary Biology, University of Arizona, Tucson, AZ 85721; iPlant Collaborative, Tucson, AZ 85721;
authors.forename: Brad
authors.initials: B
authors.lastname: Boyle
authors.affiliation: Department of Ecology and Evolutionary Biology, University of Arizona, Tucson, AZ 85721;
authors.forename: Vanessa
authors.initials: V
authors.lastname: Buzzard
authors.affiliation: Department of Computer Science and Information Systems, Bradley University, Peoria, IL 61625;
authors.forename: Steven
authors.initials: S
authors.lastname: Dolins
authors.affiliation: Missouri Botanical Garden, St. Louis, MO 63166;
authors.forename: Peter M
authors.initials: PM
authors.lastname: Jørgensen
authors.affiliation: iPlant Collaborative, Tucson, AZ 85721; National Center for Ecological Analysis and Synthesis, University of California, Santa Barbara, CA 93106;
authors.forename: Aaron
authors.initials: A
authors.lastname: Marcuse-Kubitza
authors.affiliation: Section for Ecoinformatics and Biodiversity, Department of Bioscience and.
authors.forename: Naia
authors.initials: N
authors.lastname: Morueta-Holme
authors.affiliation: Department of Biology, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599;
authors.forename: Robert K
authors.initials: RK
authors.lastname: Peet
authors.affiliation: Yale-NUS College, Republic of Singapore 138614;
authors.forename: William H
authors.initials: WH
authors.lastname: Piel
authors.affiliation: National Center for Ecological Analysis and Synthesis, University of California, Santa Barbara, CA 93106;
authors.forename: James
authors.initials: J
authors.lastname: Regetz
authors.affiliation: National Center for Ecological Analysis and Synthesis, University of California, Santa Barbara, CA 93106;
authors.forename: Mark
authors.initials: M
authors.lastname: Schildhauer
authors.affiliation: Landcare Research, Lincoln 7640, New Zealand;
authors.forename: Nick
authors.initials: N
authors.lastname: Spencer
authors.affiliation: New York Botanical Garden, Bronx, NY 10458; and.
authors.forename: Barbara
authors.initials: B
authors.lastname: Thiers
authors.affiliation: Landcare Research, Lincoln 7640, New Zealand;
authors.forename: Susan K
authors.initials: SK
authors.lastname: Wiser
authors.affiliation: Department of Ecology and Evolutionary Biology, University of Arizona, Tucson, AZ 85721; iPlant Collaborative, Tucson, AZ 85721; Santa Fe Institute, Santa Fe, NM 87501.
authors.forename: Brian J
authors.initials: BJ
authors.lastname: Enquist
mesh_terms: D044822:Biodiversity; D008954:Models, Biological; D018521:Plant Physiological Phenomena; D019655:Quantitative Trait, Heritable; D014197:Trees / Q000502:physiology*