Limits...
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.

Show MeSH
Relationship between species diversity and functional diversity for different types of reef habitats.Functional diversity (number of functions/transect, DS functional classification scheme) as a function of species diversity (number of species/transect) for each of the six clusters (three per reef type) obtained after the hierarchical classifications of transects according to their transect-scale habitat characteristics (see Table 3). DS: diet×size.
© Copyright Policy
Related In: Results  -  Collection


getmorefigures.php?uid=PMC3198825&req=5

pone-0026735-g005: Relationship between species diversity and functional diversity for different types of reef habitats.Functional diversity (number of functions/transect, DS functional classification scheme) as a function of species diversity (number of species/transect) for each of the six clusters (three per reef type) obtained after the hierarchical classifications of transects according to their transect-scale habitat characteristics (see Table 3). DS: diet×size.

Mentions: For each reef type, the transects could be classified into three distinct habitat clusters (Table 3). On barrier reefs, cluster 1 grouped transects with a high percentage of live corals, coral shelters, and hard bottoms, high habitat diversity and complexity, and a low percentage of soft bottoms. Cluster 3 contained transects with the opposite characteristics, notably with a high percentage of soft bottoms, and cluster 2 displayed intermediate values (Table 3). The clustering was similar on patch reefs. Habitat cluster 4 was dominated by soft bottoms, cluster 6 by hard substrate components and cluster 5 was characterized by fairly similar proportions of soft and hard substrates (Table 3). Despite these distinct habitat characteristics, the relationships between functional and species diversity were not significantly different between the six habitat clusters (ANCOVA, P>0.05 for all functional classification schemes, Figure 5).


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 and functional diversity for different types of reef habitats.Functional diversity (number of functions/transect, DS functional classification scheme) as a function of species diversity (number of species/transect) for each of the six clusters (three per reef type) obtained after the hierarchical classifications of transects according to their transect-scale habitat characteristics (see Table 3). DS: diet×size.
© Copyright Policy
Related In: Results  -  Collection

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

pone-0026735-g005: Relationship between species diversity and functional diversity for different types of reef habitats.Functional diversity (number of functions/transect, DS functional classification scheme) as a function of species diversity (number of species/transect) for each of the six clusters (three per reef type) obtained after the hierarchical classifications of transects according to their transect-scale habitat characteristics (see Table 3). DS: diet×size.
Mentions: For each reef type, the transects could be classified into three distinct habitat clusters (Table 3). On barrier reefs, cluster 1 grouped transects with a high percentage of live corals, coral shelters, and hard bottoms, high habitat diversity and complexity, and a low percentage of soft bottoms. Cluster 3 contained transects with the opposite characteristics, notably with a high percentage of soft bottoms, and cluster 2 displayed intermediate values (Table 3). The clustering was similar on patch reefs. Habitat cluster 4 was dominated by soft bottoms, cluster 6 by hard substrate components and cluster 5 was characterized by fairly similar proportions of soft and hard substrates (Table 3). Despite these distinct habitat characteristics, the relationships between functional and species diversity were not significantly different between the six habitat clusters (ANCOVA, P>0.05 for all functional classification schemes, Figure 5).

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