Niche Overlap and the Potential for Competition and Intraguild Predation Between Size‐Structured Populations

Wissinger, Scott A.

doi:10.2307/1940688

Cited by 152 publications

(124 citation statements)

References 73 publications

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“…Such confounding effects can be even more amplified when individual growth rates (and mortality rates) are higher in smaller individuals (as in our study species), because treatments would rapidly diverge through time. Furthermore, neither density nor total biomass is ever constant across stage classes within in our study species (Wissinger 1992;V. H. W. Rudolf, unpublished data), and keeping total biomass constant would lead to unrealistically high densities of small stages and experimental artifacts.…”

Section: Experimental Designmentioning

confidence: 91%

“…First, this generalist predator is one of the most abundant and widespread dragonflies in North America and is known to strongly impact the structure of fishless pond communities (Van Buskirk 1988, Wilbur and Fauth 1990, McPeek 1998. Secondly, individuals increase more than 17-fold in length during development and the stage structure of the population changes during the course of a season (Wissinger 1992; V. H. W. Rudolf, personal observation). Third, our preliminary stable isotope analysis of natural populations indicates that its trophic position strongly increases with size (V. H. W. Rudolf, unpublished data).…”

Section: Focal Organismsmentioning

confidence: 99%

“…Given such functional differences across ontogenetic stages, any changes in the population size structure could strongly alter the functional role of a species and therefore its impact on the ecosystem. The size structure of populations often varies considerably within a season (Wissinger 1988, 1992, Urban 2007, Rudolf 2012, or over years and decades (Osenberg et al 1992, Persson et al 2003, or differs between populations in different habitats (Osenberg et al 1992) due to changes (natural or anthropogenic) in environmental conditions. Thus, understanding the consequences of this ontogenetic diversity for the dynamics of communities and ecosystem processes is critical to understand the functional role of species in natural communities.…”

Section: Introductionmentioning

confidence: 99%

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Ontogenetic functional diversity: Size structure of a keystone predator drives functioning of a complex ecosystem

Rudolf

Rasmussen

2013

Ecology

107

118

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Abstract. A central challenge in community ecology is to understand the connection between biodiversity and the functioning of ecosystems. While traditional approaches have largely focused on species-level diversity, increasing evidence indicates that there exists substantial ecological diversity among individuals within species. By far, the largest source of this intraspecific diversity stems from variation among individuals in ontogenetic stage and size. Although such ontogenetic shifts are ubiquitous in natural communities, whether and how they scale up to influence the structure and functioning of complex ecosystems is largely unknown. Here we take an experimental approach to examine the consequences of ontogenetic niche shifts for the structure of communities and ecosystem processes. In particular we experimentally manipulated the stage structure in a keystone predator, larvae of the dragonfly Anax junius, in complex experimental pond communities to test whether changes in the population stage or size structure of a keystone species scale up to alter community structure and ecosystem processes, and how functional differences scale with relative differences in size among stages.We found that the functional role of A. junius was stage-specific. Altering what stages were present in a pond led to concurrent changes in community structure, primary producer biomass (periphyton and phytoplankton), and ultimately altered ecosystem processes (respiration and net primary productivity), indicating a strong, but stage-specific, trophic cascade. Interestingly, the stage-specific effects did not simply scale with size or biomass of the predator, but instead indicated clear ontogenetic niche shifts in ecological interactions. Thus, functional differences among stages within a keystone species scaled up to alter the functioning of entire ecosystems. Therefore, our results indicate that the classical approach of assuming an average functional role of a species can be misleading because functional roles are dynamic and will change with shifts in the stage structure of the species. In general this emphasizes the importance of accounting for functional diversity below the species level to predict how natural and anthropogenic changes alter the functioning of natural ecosystems.

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Section: Experimental Designmentioning

confidence: 91%

Section: Focal Organismsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Ontogenetic functional diversity: Size structure of a keystone predator drives functioning of a complex ecosystem

Rudolf

Rasmussen

2013

Ecology

107

118

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“…However, when predators differ substantially in size, such substitutive designs lead to dramatic differences in either biomass or density, and conclusions about identity effects are likely to be confounded by these differences 37,38 . Moreover, neither density nor total biomass are ever constant across stage classes within our study species 39 , and keeping total biomass constant would lead to unrealistically high densities of small stages and experimental artifacts. Consequently, in systems where the effects of individuals on the ecosystem are largely driven by body size, there is a high risk of misinterpreting results when using traditional substitutive designs 37,40 .…”

Section: Methodsmentioning

confidence: 99%

Population structure determines functional differences among species and ecosystem processes

2013

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Linking the structure of communities to ecosystem functioning has been a perennial challenge in ecology. Studies on ecosystem function are traditionally focused on changes in species composition. However, this species-centric approach neglects the often dramatic changes in the ecology of organisms during their development, thereby limiting our ability to link the structure of populations and communities to the functioning of natural ecosystems. Here we experimentally demonstrate that the impact of organisms on community structure and ecosystem processes often differ more among developmental stages within a species than between species, contrary to current assumptions. Importantly, we show that functional differences between species vary depending on the specific demographic structure of predators. One important implication is that changes in the demography of populations can strongly alter the functional composition of communities and change ecosystem processes long before any species are extirpated from communities.

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“…Size-asymmetric cannibalism has been documented in many taxa, but particularly fish (e.g., Skov & Koed, 2004) and aquatic invertebrates (Marshall et al, 2005). Wissinger (1992) suggests that cannibalism is most likely to occur in size-structured species with overlapping generations in time and space.…”

Section: Introductionmentioning

confidence: 99%

Habitat-mediated cannibalism and microhabitat restriction in the stream invertebrate Gammarus pulex

et al. 2007

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In cannibalistic species, small individuals often shift habitats to minimize risk of predation by larger conspecifics. The availability of diverse size-structured habitats may mediate the incidence of cannibalism by larger individuals on smaller individuals and increase fitness of smaller individuals. We tested these hypotheses in a series of laboratory studies with Gammarus pulex, a freshwater amphipod inhabiting substrates with varying interstitial pore space sizes. In the absence of larger, potentially cannibalistic individuals, small Gammarus actively used all pore space sizes offered. They used only substrates containing food and preferred food items that provided cover to food items that did not. In the presence of larger G. pulex, small individuals almost exclusively used smaller pore spaces from which larger individuals were excluded. Small individual survival was significantly lower in the presence of larger Gammarus than in controls without larger individuals regardless of substrate size, but availability of mixed pore sizes significantly increased survival. Food consumption and growth per individual were not affected by the presence of larger individuals or substrate composition. Our results suggest that the distribution and availability of complex and high-quality habitats may affect the occurrence and significance of cannibalism in size-structured populations.

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Niche Overlap and the Potential for Competition and Intraguild Predation Between Size‐Structured Populations

Cited by 152 publications

References 73 publications

Ontogenetic functional diversity: Size structure of a keystone predator drives functioning of a complex ecosystem

Ontogenetic functional diversity: Size structure of a keystone predator drives functioning of a complex ecosystem

Population structure determines functional differences among species and ecosystem processes

Habitat-mediated cannibalism and microhabitat restriction in the stream invertebrate Gammarus pulex

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