Species Turnover and the Regulation of Trophic Structure

Leibold, Mathew A.; Chase, Jonathan M.; Shurin, Jonathan B.; Downing, Amy L.

doi:10.1146/annurev.ecolsys.28.1.467

Cited by 321 publications

(408 citation statements)

References 169 publications

(217 reference statements)

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“…This pattern contrasts with predictions of classical food chain models, which only account for the number or biomass of individuals and which form the basis of most current theories about biological communities. Such unstructured models do not allow for alternative equilibria and predict that the number of trophic levels changes only at invasion thresholds, where food density for a higher trophic level becomes sufficiently abundant to persist (24,25). Therefore, in such models the invasion and persistence thresholds coincide and predators are hence predicted to be always present above their invasion threshold and always go extinct below it (24,25).…”

Section: Resultsmentioning

confidence: 99%

Size-dependent life-history traits promote catastrophic collapses of top predators

Roos

Persson

2002

Proc. Natl. Acad. Sci. U.S.A.

243

237

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Catastrophic population collapses such as observed in many exploited fish populations have been argued to result from depensatory growth mechanisms (i.e., reduced reproductive success at low population densities, also known as Allee effect). Empirical support for depensation from population-level data is, however, hard to obtain and inconclusive. Using a size-structured, individualbased model we show that catastrophic population collapses may nonetheless be an intrinsic property of many communities, because of two general aspects of individual life history: size-and fooddependent individual growth and individual mortality decreasing with body size. Positive density dependence, characteristic for depensatory growth mechanisms and catastrophic behavior, results as a direct and robust consequence of the interplay between these individual life-history traits, which are commonly found in many species.R ecent studies on lakes, coral reefs, oceans, forests, and arid lands document drastic changes in the composition of the biological community and the functioning of the ecosystem (1, 2). One view is that these abrupt changes represent catastrophic shifts between contrasting states of the system that are both stable equilibria (1, 2). The collapse of several exploited fish stocks, which fail to recover after over-fishing and a closure of fisheries, could be interpreted as such a shift, if the community state without the exploited fish species represents a stable equilibrium (2-4). If the interpretation in terms of alternative stable equilibria is correct, our view of how these ecological systems function and how to manage them is heavily affected (5). Models of biological communities show that the extinct state may be stable if the exploited species exhibits a reduced population growth capacity at low densities (2, 6). Such depensatory growth (also known as Allee effect, positive or inverse densitydependence) will prevent rebound of the population after a crash. Population-level data do not unambiguously support or refute the presence of depensatory mechanisms in natural systems (6-9). Estimates of spawner abundance and the number of surviving progeny for 128 fish stocks indicated only 3 stocks with significant depensation (7). More advanced statistical testing of these stock-recruitment relations showed that the probability of depensation was nonetheless significant (8). Also, 15 years after a collapse of the population most of the exploited fish stocks have yet to recover. Assuming that management strategies have been implemented to reduce fishing mortality after a collapse, such a lack of recovery indicates a reduced capacity to rebound from low densities (9).Community models incorporating depensatory mechanisms do so as an assumption (7), which is justified by verbal arguments. For example, it is argued that depensatory growth may result from adult individuals negatively affecting competitors of their own juveniles (6), from reduced cooperative behavior at low densities (10), or predator swamping at high density (11)...

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Section: Resultsmentioning

confidence: 99%

Size-dependent life-history traits promote catastrophic collapses of top predators

Roos

Persson

2002

Proc. Natl. Acad. Sci. U.S.A.

243

237

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“…1-5 and reviewed in refs. [6][7][8][9]. Traditionally, ecologists have ascribed these indirect effects of predators almost solely to their effects on prey density.…”

mentioning

confidence: 99%

The contribution of trait-mediated indirect effects to the net effects of a predator

Peacor

Werner

2001

Proc. Natl. Acad. Sci. U.S.A.

401

428

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Many prey modify traits in response to predation risk and this modification of traits can influence the prey's resource acquisition rate. A predator thus can have a ''nonlethal'' impact on prey that can lead to indirect effects on other community members. Such indirect interactions are termed trait-mediated indirect interactions because they arise from a predator's influence on prey traits, rather than prey density. Because such nonlethal predator effects are immediate, can influence the entire prey population, and can occur over the entire prey lifetime, we argue that nonlethal predator effects are likely to contribute strongly to the net indirect effects of predators (i.e., nonlethal effects may be comparable in magnitude to those resulting from killing prey). This prediction was supported by an experiment in which the indirect effects of a larval dragonfly (Anax sp.) predator on large bullfrog tadpoles (Rana catesbeiana), through nonlethal effects on competing small bullfrog tadpoles, were large relative to indirect effects caused by density reduction of the small tadpoles (the lethal effect). Treatments in which lethal and nonlethal effects of Anax were manipulated independently indicated that this result was robust for a large range of different combinations of lethal and nonlethal effects. Because many, if not most, prey modify traits in response to predators, our results suggest that the magnitude of interaction coefficients between two species may often be dynamically related to changes in other community members, and that many indirect effects previously attributed to the lethal effects of predators may instead be due to shifts in traits of surviving prey. I t has long been recognized that the effects of a predator can extend further than the species they consume. For example, killing a prey can indirectly affect other predators of the prey (causing exploitative competition) and resources of the prey (causing trophic cascades and keystone predator effects). Such indirect effects can have a large influence on the structure and dynamics of ecological communities (refs. 1-5 and reviewed in refs. 6-9). Traditionally, ecologists have ascribed these indirect effects of predators almost solely to their effects on prey density.Predators, however, also interact with prey by inducing changes in prey phenotype. Prey often respond to changes in predator density by modifying traits as diverse as behavior (10-12), morphology (12), and life history (12). These traitchanges may, in turn, affect other species interacting with these prey (13-18). For example, a predator-induced reduction in prey activity (making it a less efficient forager) may indirectly affect prey resources and consequently prey competitors. To distinguish such ''nonlethal'' predator effects from density-mediated indirect interactions (DMIIs, ref. 17) caused by chains of effects on density (''lethal'' effects) alone, these types of indirect interactions have been termed trait-mediated indirect interactions (TMIIs, ref. 17).Evidence is accumulating t...

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“…The results from these grouped analyses did not diVer from results obtained by lumping protozoans into a single trophic level. Moreover, for lower trophic levels containing edible and inedible prey, increasing productivity is less likely to benefit consumer biomass, because it is the inedible taxa that primarily benefit from enhanced productivity (Leibold et al 1997). Thus, lumping species with different edibilities into the lowest trophic level (protozoans) would make it more difficult to detect differences in productivity-richness relationships within the consumer (i.e., invertebrate) trophic level.…”

Section: Tree Hole Samplingmentioning

confidence: 99%

“…Biomass within communities is jointly determined by resource control of higher trophic levels and consumer control of lower trophic levels (Lindeman 1942;Fretwell 1977;Oksanen et al 1981;Leibold et al 1997). This theoretical work predicts that, for a single trophic level (producers), productivity has a positive effect on biomass.…”

Section: Introductionmentioning

confidence: 97%

“…To predict the effects of productivity on richness of multi-trophic level systems, we considered biomass partitioning among trophic levels and its relationship to productivity (Leibold et al 1997). Biomass within communities is jointly determined by resource control of higher trophic levels and consumer control of lower trophic levels (Lindeman 1942;Fretwell 1977;Oksanen et al 1981;Leibold et al 1997).…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Richness–productivity relationships between trophic levels in a detritus-based system: significance of abundance and trophic linkage

Yee

Kneitel

et al. 2007

Oecologia

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Most theoretical and empirical studies of productivity-species richness relationships fail to consider linkages among trophic levels. We quantified productivity-richness relationships in detritus-based, water-filled tree-hole communities for two trophic levels: invertebrate consumers and the protozoans on which they feed. By analogy to theory for biomass partitioning among trophic levels, we predicted that consumer control would result in richness of protozoans in the lower trophic level being unaffected by increases in productivity, whereas richness of invertebrate consumers would increase with productivity. Our data were consistent with this prediction: consumer richness increased linearly, but protozoan richness was unrelated to changes in productivity. The productivity-richness relationships for all taxa combined were not necessarily consistent with relationships within each trophic level. We used path analysis to investigate the mechanisms that may produce the observed responses of trophic levels to changes in productivity. We tested the importance of the direct effect of productivity on richness and the indirect effect of productivity mediated by effects on total abundance. For protozoans, only direct effects of productivity on richness were important, but both direct and indirect effects of productivity on richness were important for invertebrates. Protozoan richness was strongly affected by top-down impacts of abundance of invertebrates. These results are consistent with theory on biomass partitioning among trophic levels and suggest a strong link between richness and abundance within and between trophic levels. Understanding how trophic level interactions determine productivity-richness relationships will likely be necessary in order for us to achieve a comprehensive understanding of the determinants of diversity.

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Species Turnover and the Regulation of Trophic Structure

Cited by 321 publications

References 169 publications

Size-dependent life-history traits promote catastrophic collapses of top predators

Size-dependent life-history traits promote catastrophic collapses of top predators

The contribution of trait-mediated indirect effects to the net effects of a predator

Richness–productivity relationships between trophic levels in a detritus-based system: significance of abundance and trophic linkage

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