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Proc Natl Acad Sci U S A. 2014 Sep 23;111(38):13757-62. doi: 10.1073/pnas.1317625111. Epub 2014 Sep 15.

Functional over-redundancy and high functional vulnerability in global fish faunas on tropical reefs.

Author information

1
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.
2
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;
3
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;
4
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;
5
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;
6
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;
7
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;
8
Marine Macroecology and Biogeography Laboratory, Universidade Federal de Santa Catarina, Florianópolis, 88040-900, Santa Catarina, Brazil;
9
Fisheries Ecology Research Laboratory, Department of Biology, University of Hawaii at Manoa, Honolulu, HI 96822;
10
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.
11
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.

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.

KEYWORDS:

coral reefs; fish ecology

PMID:
25225388
PMCID:
PMC4183327
DOI:
10.1073/pnas.1317625111
[Indexed for MEDLINE]
Free PMC Article

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