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Species richness and trophic diversity increase decomposition in a co-evolved food web.

Baiser B, Ardeshiri RS, Ellison AM - PLoS ONE (2011)

Bottom Line: Knowledge of how this biodiversity relates to ecosystem functioning is important for understanding the maintenance of diversity and the potential effects of species losses and gains on ecosystems.We show that species richness and trophic diversity underlie strong linkages between food web structure and dynamics that influence ecosystem functioning.The importance of trophic diversity and species interactions in determining how biodiversity relates to ecosystem functioning suggests that simply focusing on species richness does not give a complete picture as to how ecosystems may change with the loss or gain of species.

View Article: PubMed Central - PubMed

Affiliation: Harvard Forest, Harvard University, Petersham, Massachusetts, United States of America. bbaiser@fas.harvard.edu

ABSTRACT
Ecological communities show great variation in species richness, composition and food web structure across similar and diverse ecosystems. Knowledge of how this biodiversity relates to ecosystem functioning is important for understanding the maintenance of diversity and the potential effects of species losses and gains on ecosystems. While research often focuses on how variation in species richness influences ecosystem processes, assessing species richness in a food web context can provide further insight into the relationship between diversity and ecosystem functioning and elucidate potential mechanisms underpinning this relationship. Here, we assessed how species richness and trophic diversity affect decomposition rates in a complete aquatic food web: the five trophic level web that occurs within water-filled leaves of the northern pitcher plant, Sarracenia purpurea. We identified a trophic cascade in which top-predators--larvae of the pitcher-plant mosquito--indirectly increased bacterial decomposition by preying on bactivorous protozoa. Our data also revealed a facultative relationship in which larvae of the pitcher-plant midge increased bacterial decomposition by shredding detritus. These important interactions occur only in food webs with high trophic diversity, which in turn only occur in food webs with high species richness. We show that species richness and trophic diversity underlie strong linkages between food web structure and dynamics that influence ecosystem functioning. The importance of trophic diversity and species interactions in determining how biodiversity relates to ecosystem functioning suggests that simply focusing on species richness does not give a complete picture as to how ecosystems may change with the loss or gain of species.

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Best-fit path models describing decomposition dynamics in the Sarracenia food web.The indirect full food web model including ant mass (A) was the top overall model and the midge sampling effect model including ant mass (B) was the top sampling effect path model explaining decomposition by bacteria (Decomp) in the Sarracenia food web. Standardized path coefficients are shown for each link and arrows are proportional to the magnitude of the coefficient. Solid black lines indicate significant (P<0.05) positive relationships and solid red lines indicate significant negative relationships. Dashed lines indicate non-significant relationships. The R2 value shows the amount of variation in decomposition explained by the path model.
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pone-0020672-g003: Best-fit path models describing decomposition dynamics in the Sarracenia food web.The indirect full food web model including ant mass (A) was the top overall model and the midge sampling effect model including ant mass (B) was the top sampling effect path model explaining decomposition by bacteria (Decomp) in the Sarracenia food web. Standardized path coefficients are shown for each link and arrows are proportional to the magnitude of the coefficient. Solid black lines indicate significant (P<0.05) positive relationships and solid red lines indicate significant negative relationships. Dashed lines indicate non-significant relationships. The R2 value shows the amount of variation in decomposition explained by the path model.

Mentions: Sampling effect and food web path models were used to further explore how species richness and TD increase decomposition. The top ranked model was the indirect full food web model which also included ant mass (Fig. 3a, Table 1). This model revealed three significant pathways (regression coefficients P<0.05) and explained 39% of the variation in decomposition. The first pathway was a trophic cascade in which mosquito larvae had a negative effect on protozoan abundance, which in turn had a negative effect on decomposition by bacteria. Although we did not measure bacterial abundance directly, a trophic cascade induced by mosquito predation has been demonstrated repeatedly in the Sarracenia food web [33], [36], [37]. The copepod, which has the same prey as the mosquito larvae, had no significant influence on prey items or decomposition (Fig. 3a).


Species richness and trophic diversity increase decomposition in a co-evolved food web.

Baiser B, Ardeshiri RS, Ellison AM - PLoS ONE (2011)

Best-fit path models describing decomposition dynamics in the Sarracenia food web.The indirect full food web model including ant mass (A) was the top overall model and the midge sampling effect model including ant mass (B) was the top sampling effect path model explaining decomposition by bacteria (Decomp) in the Sarracenia food web. Standardized path coefficients are shown for each link and arrows are proportional to the magnitude of the coefficient. Solid black lines indicate significant (P<0.05) positive relationships and solid red lines indicate significant negative relationships. Dashed lines indicate non-significant relationships. The R2 value shows the amount of variation in decomposition explained by the path model.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC3108618&req=5

pone-0020672-g003: Best-fit path models describing decomposition dynamics in the Sarracenia food web.The indirect full food web model including ant mass (A) was the top overall model and the midge sampling effect model including ant mass (B) was the top sampling effect path model explaining decomposition by bacteria (Decomp) in the Sarracenia food web. Standardized path coefficients are shown for each link and arrows are proportional to the magnitude of the coefficient. Solid black lines indicate significant (P<0.05) positive relationships and solid red lines indicate significant negative relationships. Dashed lines indicate non-significant relationships. The R2 value shows the amount of variation in decomposition explained by the path model.
Mentions: Sampling effect and food web path models were used to further explore how species richness and TD increase decomposition. The top ranked model was the indirect full food web model which also included ant mass (Fig. 3a, Table 1). This model revealed three significant pathways (regression coefficients P<0.05) and explained 39% of the variation in decomposition. The first pathway was a trophic cascade in which mosquito larvae had a negative effect on protozoan abundance, which in turn had a negative effect on decomposition by bacteria. Although we did not measure bacterial abundance directly, a trophic cascade induced by mosquito predation has been demonstrated repeatedly in the Sarracenia food web [33], [36], [37]. The copepod, which has the same prey as the mosquito larvae, had no significant influence on prey items or decomposition (Fig. 3a).

Bottom Line: Knowledge of how this biodiversity relates to ecosystem functioning is important for understanding the maintenance of diversity and the potential effects of species losses and gains on ecosystems.We show that species richness and trophic diversity underlie strong linkages between food web structure and dynamics that influence ecosystem functioning.The importance of trophic diversity and species interactions in determining how biodiversity relates to ecosystem functioning suggests that simply focusing on species richness does not give a complete picture as to how ecosystems may change with the loss or gain of species.

View Article: PubMed Central - PubMed

Affiliation: Harvard Forest, Harvard University, Petersham, Massachusetts, United States of America. bbaiser@fas.harvard.edu

ABSTRACT
Ecological communities show great variation in species richness, composition and food web structure across similar and diverse ecosystems. Knowledge of how this biodiversity relates to ecosystem functioning is important for understanding the maintenance of diversity and the potential effects of species losses and gains on ecosystems. While research often focuses on how variation in species richness influences ecosystem processes, assessing species richness in a food web context can provide further insight into the relationship between diversity and ecosystem functioning and elucidate potential mechanisms underpinning this relationship. Here, we assessed how species richness and trophic diversity affect decomposition rates in a complete aquatic food web: the five trophic level web that occurs within water-filled leaves of the northern pitcher plant, Sarracenia purpurea. We identified a trophic cascade in which top-predators--larvae of the pitcher-plant mosquito--indirectly increased bacterial decomposition by preying on bactivorous protozoa. Our data also revealed a facultative relationship in which larvae of the pitcher-plant midge increased bacterial decomposition by shredding detritus. These important interactions occur only in food webs with high trophic diversity, which in turn only occur in food webs with high species richness. We show that species richness and trophic diversity underlie strong linkages between food web structure and dynamics that influence ecosystem functioning. The importance of trophic diversity and species interactions in determining how biodiversity relates to ecosystem functioning suggests that simply focusing on species richness does not give a complete picture as to how ecosystems may change with the loss or gain of species.

Show MeSH
Related in: MedlinePlus