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Functional redundancy patterns reveal non-random assembly rules in a species-rich marine assemblage.

Guillemot N, Kulbicki M, Chabanet P, Vigliola L - PLoS ONE (2011)

Bottom Line: First, we found that the relationship between functional and species diversity displayed a non-asymptotic power-shaped curve, implying that rare functions and species mainly occur in highly diverse assemblages.Last, we found little effect of habitat on the shape of the functional-species diversity relationship and on the redundancy of functions, although habitat is known to largely determine assemblage characteristics such as species composition, biomass, and abundance.Our study shows that low functional redundancy is characteristic of this highly diverse fish assemblage, and, therefore, that even species-rich ecosystems such as coral reefs may be vulnerable to the removal of a few keystone species.

View Article: PubMed Central - PubMed

Affiliation: UR-CoRéUs, Institut de Recherche pour le Développement, Noumea, New Caledonia. nicolas.guillemot@gmail.com

ABSTRACT
The relationship between species and the functional diversity of assemblages is fundamental in ecology because it contains key information on functional redundancy, and functionally redundant ecosystems are thought to be more resilient, resistant and stable. However, this relationship is poorly understood and undocumented for species-rich coastal marine ecosystems. Here, we used underwater visual censuses to examine the patterns of functional redundancy for one of the most diverse vertebrate assemblages, the coral reef fishes of New Caledonia, South Pacific. First, we found that the relationship between functional and species diversity displayed a non-asymptotic power-shaped curve, implying that rare functions and species mainly occur in highly diverse assemblages. Second, we showed that the distribution of species amongst possible functions was significantly different from a random distribution up to a threshold of ∼90 species/transect. Redundancy patterns for each function further revealed that some functions displayed fast rates of increase in redundancy at low species diversity, whereas others were only becoming redundant past a certain threshold. This suggested non-random assembly rules and the existence of some primordial functions that would need to be fulfilled in priority so that coral reef fish assemblages can gain a basic ecological structure. Last, we found little effect of habitat on the shape of the functional-species diversity relationship and on the redundancy of functions, although habitat is known to largely determine assemblage characteristics such as species composition, biomass, and abundance. Our study shows that low functional redundancy is characteristic of this highly diverse fish assemblage, and, therefore, that even species-rich ecosystems such as coral reefs may be vulnerable to the removal of a few keystone species.

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Relationship between species diversity (number of species/transect) and functional diversity (number of functions/transect).A: Linear, power, asymptotic and logistic regressions are shown for the DS classification scheme. B: only the best model (power, see Table 2) is shown for each of the three classification schemes. Dotted line indicates 1∶1 line for both plots. DS: diet×size; DSH: diet×size×home range; DSHG: diet×size×home range×gregariousness.
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pone-0026735-g003: Relationship between species diversity (number of species/transect) and functional diversity (number of functions/transect).A: Linear, power, asymptotic and logistic regressions are shown for the DS classification scheme. B: only the best model (power, see Table 2) is shown for each of the three classification schemes. Dotted line indicates 1∶1 line for both plots. DS: diet×size; DSH: diet×size×home range; DSHG: diet×size×home range×gregariousness.

Mentions: A total of 421 species belonging to 142 genera and 47 families were observed in the study area. These corresponded to 20 observed functions for the DS classification scheme, 46 for DSH, and 96 for DSHG. On a single transect, between 27 and 112 species corresponding to 7–18 (DS), 13–39 (DSH) and 19–63 (DSHG) functions were observed. For each classification, there was a significant (P<0.05) and positive correlation between the number of functions and the number of species (Spearman R = 0.76, 0.88 and 0.95 for DS, DSH and DSHG, respectively). Consistently across classification schemes, the relationships between functional and species diversity were non-linear (log-likelihood ratio tests, P<0.001 for all linear versus power model comparisons) and best described by a power model (Table 2, Figure 3).


Functional redundancy patterns reveal non-random assembly rules in a species-rich marine assemblage.

Guillemot N, Kulbicki M, Chabanet P, Vigliola L - PLoS ONE (2011)

Relationship between species diversity (number of species/transect) and functional diversity (number of functions/transect).A: Linear, power, asymptotic and logistic regressions are shown for the DS classification scheme. B: only the best model (power, see Table 2) is shown for each of the three classification schemes. Dotted line indicates 1∶1 line for both plots. DS: diet×size; DSH: diet×size×home range; DSHG: diet×size×home range×gregariousness.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC3198825&req=5

pone-0026735-g003: Relationship between species diversity (number of species/transect) and functional diversity (number of functions/transect).A: Linear, power, asymptotic and logistic regressions are shown for the DS classification scheme. B: only the best model (power, see Table 2) is shown for each of the three classification schemes. Dotted line indicates 1∶1 line for both plots. DS: diet×size; DSH: diet×size×home range; DSHG: diet×size×home range×gregariousness.
Mentions: A total of 421 species belonging to 142 genera and 47 families were observed in the study area. These corresponded to 20 observed functions for the DS classification scheme, 46 for DSH, and 96 for DSHG. On a single transect, between 27 and 112 species corresponding to 7–18 (DS), 13–39 (DSH) and 19–63 (DSHG) functions were observed. For each classification, there was a significant (P<0.05) and positive correlation between the number of functions and the number of species (Spearman R = 0.76, 0.88 and 0.95 for DS, DSH and DSHG, respectively). Consistently across classification schemes, the relationships between functional and species diversity were non-linear (log-likelihood ratio tests, P<0.001 for all linear versus power model comparisons) and best described by a power model (Table 2, Figure 3).

Bottom Line: First, we found that the relationship between functional and species diversity displayed a non-asymptotic power-shaped curve, implying that rare functions and species mainly occur in highly diverse assemblages.Last, we found little effect of habitat on the shape of the functional-species diversity relationship and on the redundancy of functions, although habitat is known to largely determine assemblage characteristics such as species composition, biomass, and abundance.Our study shows that low functional redundancy is characteristic of this highly diverse fish assemblage, and, therefore, that even species-rich ecosystems such as coral reefs may be vulnerable to the removal of a few keystone species.

View Article: PubMed Central - PubMed

Affiliation: UR-CoRéUs, Institut de Recherche pour le Développement, Noumea, New Caledonia. nicolas.guillemot@gmail.com

ABSTRACT
The relationship between species and the functional diversity of assemblages is fundamental in ecology because it contains key information on functional redundancy, and functionally redundant ecosystems are thought to be more resilient, resistant and stable. However, this relationship is poorly understood and undocumented for species-rich coastal marine ecosystems. Here, we used underwater visual censuses to examine the patterns of functional redundancy for one of the most diverse vertebrate assemblages, the coral reef fishes of New Caledonia, South Pacific. First, we found that the relationship between functional and species diversity displayed a non-asymptotic power-shaped curve, implying that rare functions and species mainly occur in highly diverse assemblages. Second, we showed that the distribution of species amongst possible functions was significantly different from a random distribution up to a threshold of ∼90 species/transect. Redundancy patterns for each function further revealed that some functions displayed fast rates of increase in redundancy at low species diversity, whereas others were only becoming redundant past a certain threshold. This suggested non-random assembly rules and the existence of some primordial functions that would need to be fulfilled in priority so that coral reef fish assemblages can gain a basic ecological structure. Last, we found little effect of habitat on the shape of the functional-species diversity relationship and on the redundancy of functions, although habitat is known to largely determine assemblage characteristics such as species composition, biomass, and abundance. Our study shows that low functional redundancy is characteristic of this highly diverse fish assemblage, and, therefore, that even species-rich ecosystems such as coral reefs may be vulnerable to the removal of a few keystone species.

Show MeSH
Related in: MedlinePlus