Limits...
Consumers control diversity and functioning of a natural marine ecosystem.

Altieri AH, Trussell GC, Ewanchuk PJ, Bernatchez G, Bracken ME - PLoS ONE (2009)

Bottom Line: Seaweed species evenness and biomass-specific primary productivity (mg O(2) h(-1) g(-1)) were higher in tide pools with snails because snails preferentially consumed an otherwise dominant seaweed species that can reduce biomass-specific productivity rates of algal assemblages.Although snails reduced overall seaweed biomass in tide pools, they did not affect gross primary productivity at the scale of tide pools (mg O(2) h(-1) pool(-1) or mg O(2) h(-1) m(-2)) because of the enhanced biomass-specific productivity associated with grazer-mediated increases in algal evenness.Our results suggest that increased attention to trophic interactions, diversity measures other than richness, and particularly the effects of consumers on evenness and primary productivity, will improve our understanding of the relationship between diversity and ecosystem functioning and allow more effective links between experimental results and real-world changes in biodiversity.

View Article: PubMed Central - PubMed

Affiliation: Marine Science Center, Northeastern University, Nahant, Massachusetts, United States of America.

ABSTRACT

Background: Our understanding of the functional consequences of changes in biodiversity has been hampered by several limitations of previous work, including limited attention to trophic interactions, a focus on species richness rather than evenness, and the use of artificially assembled communities.

Methodology and principal findings: In this study, we manipulated the density of an herbivorous snail in natural tide pools and allowed seaweed communities to assemble in an ecologically relevant and non-random manner. Seaweed species evenness and biomass-specific primary productivity (mg O(2) h(-1) g(-1)) were higher in tide pools with snails because snails preferentially consumed an otherwise dominant seaweed species that can reduce biomass-specific productivity rates of algal assemblages. Although snails reduced overall seaweed biomass in tide pools, they did not affect gross primary productivity at the scale of tide pools (mg O(2) h(-1) pool(-1) or mg O(2) h(-1) m(-2)) because of the enhanced biomass-specific productivity associated with grazer-mediated increases in algal evenness.

Significance: Our results suggest that increased attention to trophic interactions, diversity measures other than richness, and particularly the effects of consumers on evenness and primary productivity, will improve our understanding of the relationship between diversity and ecosystem functioning and allow more effective links between experimental results and real-world changes in biodiversity.

Show MeSH
Mean (+SE) abundance of tidepool algae at different snail densities.Although high (250 per m2) and low (150 per m2) snail densities affected the abundance of specific algae differently, they generated similar patterns of species evenness and productivity. Symbols above bars indicate species-specific effects of density on cover: “***” indicates P<0.0001, “*” indicates P<0.05, and “NS” indicates that there were no differences between treatments for that seaweed species.
© Copyright Policy
Related In: Results  -  Collection


getmorefigures.php?uid=PMC2668074&req=5

pone-0005291-g003: Mean (+SE) abundance of tidepool algae at different snail densities.Although high (250 per m2) and low (150 per m2) snail densities affected the abundance of specific algae differently, they generated similar patterns of species evenness and productivity. Symbols above bars indicate species-specific effects of density on cover: “***” indicates P<0.0001, “*” indicates P<0.05, and “NS” indicates that there were no differences between treatments for that seaweed species.

Mentions: Snails did not influence any metrics of diversity other than evenness. Species richness (S), Shannon-Wiener's H′, and Simpson's D did not vary across snail treatments (P≥0.73 for all analyses, Table S1). Species identity was also similar across all levels of snail grazing, with 11 of 15 algal taxa found at all 3 snail densities, and the other 4 species occurring only rarely (each in 3 or fewer of the 36 experimental tide pools). Although high and low snail densities similarly increased algal species evenness, the snail density treatments had unique effects on the relative abundance of several algal species, particularly Ulva and Scytosiphon (P<0.001, Table S3, Fig. 3).


Consumers control diversity and functioning of a natural marine ecosystem.

Altieri AH, Trussell GC, Ewanchuk PJ, Bernatchez G, Bracken ME - PLoS ONE (2009)

Mean (+SE) abundance of tidepool algae at different snail densities.Although high (250 per m2) and low (150 per m2) snail densities affected the abundance of specific algae differently, they generated similar patterns of species evenness and productivity. Symbols above bars indicate species-specific effects of density on cover: “***” indicates P<0.0001, “*” indicates P<0.05, and “NS” indicates that there were no differences between treatments for that seaweed species.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC2668074&req=5

pone-0005291-g003: Mean (+SE) abundance of tidepool algae at different snail densities.Although high (250 per m2) and low (150 per m2) snail densities affected the abundance of specific algae differently, they generated similar patterns of species evenness and productivity. Symbols above bars indicate species-specific effects of density on cover: “***” indicates P<0.0001, “*” indicates P<0.05, and “NS” indicates that there were no differences between treatments for that seaweed species.
Mentions: Snails did not influence any metrics of diversity other than evenness. Species richness (S), Shannon-Wiener's H′, and Simpson's D did not vary across snail treatments (P≥0.73 for all analyses, Table S1). Species identity was also similar across all levels of snail grazing, with 11 of 15 algal taxa found at all 3 snail densities, and the other 4 species occurring only rarely (each in 3 or fewer of the 36 experimental tide pools). Although high and low snail densities similarly increased algal species evenness, the snail density treatments had unique effects on the relative abundance of several algal species, particularly Ulva and Scytosiphon (P<0.001, Table S3, Fig. 3).

Bottom Line: Seaweed species evenness and biomass-specific primary productivity (mg O(2) h(-1) g(-1)) were higher in tide pools with snails because snails preferentially consumed an otherwise dominant seaweed species that can reduce biomass-specific productivity rates of algal assemblages.Although snails reduced overall seaweed biomass in tide pools, they did not affect gross primary productivity at the scale of tide pools (mg O(2) h(-1) pool(-1) or mg O(2) h(-1) m(-2)) because of the enhanced biomass-specific productivity associated with grazer-mediated increases in algal evenness.Our results suggest that increased attention to trophic interactions, diversity measures other than richness, and particularly the effects of consumers on evenness and primary productivity, will improve our understanding of the relationship between diversity and ecosystem functioning and allow more effective links between experimental results and real-world changes in biodiversity.

View Article: PubMed Central - PubMed

Affiliation: Marine Science Center, Northeastern University, Nahant, Massachusetts, United States of America.

ABSTRACT

Background: Our understanding of the functional consequences of changes in biodiversity has been hampered by several limitations of previous work, including limited attention to trophic interactions, a focus on species richness rather than evenness, and the use of artificially assembled communities.

Methodology and principal findings: In this study, we manipulated the density of an herbivorous snail in natural tide pools and allowed seaweed communities to assemble in an ecologically relevant and non-random manner. Seaweed species evenness and biomass-specific primary productivity (mg O(2) h(-1) g(-1)) were higher in tide pools with snails because snails preferentially consumed an otherwise dominant seaweed species that can reduce biomass-specific productivity rates of algal assemblages. Although snails reduced overall seaweed biomass in tide pools, they did not affect gross primary productivity at the scale of tide pools (mg O(2) h(-1) pool(-1) or mg O(2) h(-1) m(-2)) because of the enhanced biomass-specific productivity associated with grazer-mediated increases in algal evenness.

Significance: Our results suggest that increased attention to trophic interactions, diversity measures other than richness, and particularly the effects of consumers on evenness and primary productivity, will improve our understanding of the relationship between diversity and ecosystem functioning and allow more effective links between experimental results and real-world changes in biodiversity.

Show MeSH