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

Related in: MedlinePlus

Redundancy as a function of species diversity, for individual functions (DS functional classification scheme).A: Schematic possible trends. B: Observed trends. The plots were classified as early increase, late increase, constant increase or unclear trend (see Table 5). Least-square curves were fitted to each plot (for which the slope was significant following a linear regression) to visualise the trends. DS: diet×size.
© Copyright Policy
Related In: Results  -  Collection


getmorefigures.php?uid=PMC3198825&req=5

pone-0026735-g007: Redundancy as a function of species diversity, for individual functions (DS functional classification scheme).A: Schematic possible trends. B: Observed trends. The plots were classified as early increase, late increase, constant increase or unclear trend (see Table 5). Least-square curves were fitted to each plot (for which the slope was significant following a linear regression) to visualise the trends. DS: diet×size.

Mentions: There was a significantly positive correlation between functional redundancy and species diversity for all 20 functions of the DS classification scheme (Spearman's correlation tests, P>0.05), indicating that redundancy was generally higher in diverse assemblages. However, the slope of the relationship was significantly positive for only 13 functions (Table 5). Among these, three patterns of increase could be identified (Figure 7). First, the redundancy of some functions increased rapidly at low levels of species diversity, and then slowed down at higher levels. For instance, the redundancy of C2 and H2 increased notably between 0 and approximately 60 species, and then increased with a gentler slope past this limit (Figure 7). Second, some functions displayed slow increases of redundancy at low levels of species diversity, and faster increases at higher levels; C4 and C5 provided good examples of this pattern, with respective thresholds of approximately 50 and 70 species (Figure 7). Third, some functions, such as C3 and H4, displayed a linear pattern of increase of their redundancy as a function of species diversity (Figure 7). The remaining functions displayed unclear trends (supported by non-significant slopes and low Spearman's correlation coefficients with regard to the other functions) and corresponded to low levels of functional redundancy (Table 5, Figure 7).


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)

Redundancy as a function of species diversity, for individual functions (DS functional classification scheme).A: Schematic possible trends. B: Observed trends. The plots were classified as early increase, late increase, constant increase or unclear trend (see Table 5). Least-square curves were fitted to each plot (for which the slope was significant following a linear regression) to visualise the trends. DS: diet×size.
© Copyright Policy
Related In: Results  -  Collection

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

pone-0026735-g007: Redundancy as a function of species diversity, for individual functions (DS functional classification scheme).A: Schematic possible trends. B: Observed trends. The plots were classified as early increase, late increase, constant increase or unclear trend (see Table 5). Least-square curves were fitted to each plot (for which the slope was significant following a linear regression) to visualise the trends. DS: diet×size.
Mentions: There was a significantly positive correlation between functional redundancy and species diversity for all 20 functions of the DS classification scheme (Spearman's correlation tests, P>0.05), indicating that redundancy was generally higher in diverse assemblages. However, the slope of the relationship was significantly positive for only 13 functions (Table 5). Among these, three patterns of increase could be identified (Figure 7). First, the redundancy of some functions increased rapidly at low levels of species diversity, and then slowed down at higher levels. For instance, the redundancy of C2 and H2 increased notably between 0 and approximately 60 species, and then increased with a gentler slope past this limit (Figure 7). Second, some functions displayed slow increases of redundancy at low levels of species diversity, and faster increases at higher levels; C4 and C5 provided good examples of this pattern, with respective thresholds of approximately 50 and 70 species (Figure 7). Third, some functions, such as C3 and H4, displayed a linear pattern of increase of their redundancy as a function of species diversity (Figure 7). The remaining functions displayed unclear trends (supported by non-significant slopes and low Spearman's correlation coefficients with regard to the other functions) and corresponded to low levels of functional redundancy (Table 5, Figure 7).

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