title: Functional over-redundancy and high functional vulnerability in global fish faunas on tropical reefs.
abstract: When tropical systems lose species, they are often assumed to be buffered against declines in functional diversity by the ability of the species-rich biota to display high functional redundancy: i.e., a high number of species performing similar functions. We tested this hypothesis using a ninefold richness gradient in global fish faunas on tropical reefs encompassing 6,316 species distributed among 646 functional entities (FEs): i.e., unique combinations of functional traits. We found that the highest functional redundancy is located in the Central Indo-Pacific with a mean of 7.9 species per FE. However, this overall level of redundancy is disproportionately packed into few FEs, a pattern termed functional over-redundancy (FOR). For instance, the most speciose FE in the Central Indo-Pacific contains 222 species (out of 3,689) whereas 38% of FEs (180 out of 468) have no functional insurance with only one species. Surprisingly, the level of FOR is consistent across the six fish faunas, meaning that, whatever the richness, over a third of the species may still be in overrepresented FEs whereas more than one third of the FEs are left without insurance, these levels all being significantly higher than expected by chance. Thus, our study shows that, even in high-diversity systems, such as tropical reefs, functional diversity remains highly vulnerable to species loss. Although further investigations are needed to specifically address the influence of redundant vs. vulnerable FEs on ecosystem functioning, our results suggest that the promised benefits from tropical biodiversity may not be as strong as previously thought.
authors.affiliation: Ecologie des Systèmes Marins Côtiers, Unité Mixte de Recherche 5119, Centre National de la Recherche Scientifique-Institut de Recherche pour le Développement-Université Montpellier 2-Institut Français de Recherche pour l'Exploitation de la Mer, Université Montpellier 2, 34095 Montpellier, France; Australian Research Council Centre of Excellence for Coral Reef Studies, James Cook University, Townsville, QLD 4811, Australia; david.mouillot@univ-montp2.fr.
authors.forename: David
authors.initials: D
authors.lastname: Mouillot
authors.affiliation: Ecologie des Systèmes Marins Côtiers, Unité Mixte de Recherche 5119, Centre National de la Recherche Scientifique-Institut de Recherche pour le Développement-Université Montpellier 2-Institut Français de Recherche pour l'Exploitation de la Mer, Université Montpellier 2, 34095 Montpellier, France;
authors.forename: Sébastien
authors.initials: S
authors.lastname: Villéger
authors.affiliation: Institut de Recherche pour le Développement, Unité de Recherche 227 Biocomplexité des écosystèmes coralliens de l'Indo-Pacifique, LABEX Corail, Laboratoire Arago, BP 44, 66651 Banyuls sur Mer, France; Center for Synthesis and Analysis of Biodiversity-Fondation pour la Recherche sur la Biodiversité Immeuble Henri Poincaré, Domaine du Petit Arbois, 13857 Aix-en-Provence Cedex 3, France;
authors.forename: Valeriano
authors.initials: V
authors.lastname: Parravicini
authors.affiliation: Institut de Recherche pour le Développement, Unité de Recherche 227 Biocomplexité des écosystèmes coralliens de l'Indo-Pacifique, LABEX Corail, Laboratoire Arago, BP 44, 66651 Banyuls sur Mer, France;
authors.forename: Michel
authors.initials: M
authors.lastname: Kulbicki
authors.affiliation: Laboratorio de Ecología de Ecosistemas de Arrecifes Coralinos, Departamento de Recursos del Mar, Centro de Investigación y de Estudios Avanzados del Instituto Politécnico Nacional, Unidad Mérida, 97310 Mérida, Yucatán, Mexico;
authors.forename: Jesus Ernesto
authors.initials: JE
authors.lastname: Arias-González
authors.affiliation: Ecologie des Systèmes Marins Côtiers, Unité Mixte de Recherche 5119, Centre National de la Recherche Scientifique-Institut de Recherche pour le Développement-Université Montpellier 2-Institut Français de Recherche pour l'Exploitation de la Mer, Université Montpellier 2, 34095 Montpellier, France; Marine Macroecology and Biogeography Laboratory, Universidade Federal de Santa Catarina, Florianópolis, 88040-900, Santa Catarina, Brazil;
authors.forename: Mariana
authors.initials: M
authors.lastname: Bender
authors.affiliation: Institut de Recherche pour le Développement, Unité de Recherche 227 Biocomplexité des écosystèmes coralliens de l'Indo-Pacifique, LABEX Corail, BP 50172, 97492 Ste. Clotilde 18 Cedex, Reunion Island, France;
authors.forename: Pascale
authors.initials: P
authors.lastname: Chabanet
authors.affiliation: Marine Macroecology and Biogeography Laboratory, Universidade Federal de Santa Catarina, Florianópolis, 88040-900, Santa Catarina, Brazil;
authors.forename: Sergio R
authors.initials: SR
authors.lastname: Floeter
authors.affiliation: Fisheries Ecology Research Laboratory, Department of Biology, University of Hawaii at Manoa, Honolulu, HI 96822;
authors.forename: Alan
authors.initials: A
authors.lastname: Friedlander
authors.affiliation: Institut de Recherche pour le Développement, Unité de Recherche 227 Biocomplexité des écosystèmes coralliens de l'Indo-Pacifique, LABEX Corail, 98848 Nouméa Cedex, New Caledonia, France; and.
authors.forename: Laurent
authors.initials: L
authors.lastname: Vigliola
authors.affiliation: Australian Research Council Centre of Excellence for Coral Reef Studies, James Cook University, Townsville, QLD 4811, Australia; School of Marine and Tropical Biology, James Cook University, Townsville, QLD 4811, Australia.
authors.forename: David R
authors.initials: DR
authors.lastname: Bellwood
mesh_terms: D000818:Animals; D044822:Biodiversity; D057894:Coral Reefs; D005399:Fishes / Q000502:physiology*; D014329:Tropical Climate
keywords: coral reefs; fish ecology