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

Mouillot, David, Villéger, Sébastien, Parravicini, Valeriano, Kulbicki, Michel, Ernesto Arias-González, Jesus, Bender, Mariana, Chabanet, Pascale, Floeter, Sergio R., Friedlander, Alan, Vigliola, Laurent, and Bellwood, David R. (2014) Functional over-redundancy and high functional vulnerability in global fish faunas on tropical reefs. Proceedings of the National Academy of Sciences of the United States of America, 111 (38). pp. 13757-13762.

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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.

Item ID: 36212
Item Type: Article (Research - C1)
ISSN: 1091-6490
Keywords: fish ecology, coral reefs
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Funders: Marie Curie International Outgoing Fellowship (FISHECO), Fondation pour la Recherche sur la Biodiversité (BIODIVMED), Australian Research Council (ARC)
Projects and Grants: FISHECO agreement no. IOF-GA-2009-236316, BIODIVMED project "Center for Synthesis and Analysis of Biodiversity-General Approach to Species-Abundance Relationships"
Date Deposited: 12 Nov 2014 12:29
FoR Codes: 06 BIOLOGICAL SCIENCES > 0602 Ecology > 060205 Marine and Estuarine Ecology (incl Marine Ichthyology) @ 100%
SEO Codes: 96 ENVIRONMENT > 9605 Ecosystem Assessment and Management > 960507 Ecosystem Assessment and Management of Marine Environments @ 50%
97 EXPANDING KNOWLEDGE > 970105 Expanding Knowledge in the Environmental Sciences @ 50%
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