The Body Size Dependence of Trophic Cascades

Abstract

JSTOR is a not-for-profit service that helps scholars, researchers, and students discover, use, and build upon a wide range of content in a trusted digital archive. We use information technology and tools to increase productivity and facilitate new forms of scholarship. For more information about JSTOR, please contact support@jstor.org.. abstract: Trophic cascades are indirect positive effects of predators on resources via control of intermediate consumers. Larger-bodied predators appear to induce stronger trophic cascades (a greater rebound of resource density toward carrying capacity), but how this happens is unknown because we lack a clear depiction of how the strength of trophic cascades is determined. Using consumer resource models, we first show that the strength of a trophic cascade has an upper limit set by the interaction strength between the basal trophic group and its consumer and that this limit is approached as the interaction strength between the consumer and its predator increases. We then express the strength of a trophic cascade explicitly in terms of predator body size and use two independent parameter sets to calculate how the strength of a trophic cascade depends on predator size. Both parameter sets predict a positive effect of predator size on the strength of a trophic cascade, driven mostly by the body size dependence of the interaction strength between the first two trophic levels. Our results support previous empirical findings and suggest that the loss of larger predators will have greater consequences on trophic control and biomass structure in food webs than the loss of smaller predators.

Uncertainty principle in niche assessment: A solution to the dilemma redundancy vs. competitive exclusion, and some analytical consequences

“…This point coincides with the noticeable role conventionally granted to this indicator in ecology and evolutionary biology (see, e.g. : Brown et al, 2004;Woodward et al, 2005;Olson et al, 2009;DeLong et al, 2015), in which the increase of body size can be regarded as a general intra-and inter-eco-evolutionary block trend (Cope's Rule; see MacFadden, 1986;Kingsolver and Pfennig, 2004;Hone et al, 2005). Smallbodied organisms tend to have higher mass-specific metabolic rates in comparison with larger-bodied organisms, either at the intraor interspecific scale.…”

Protection of large predators in a marine reserve alters size-dependent prey mortality

“…Variation in body-size distributions can therefore influence the interaction strength between predator and prey [2], with the loss of larger-bodied predators causing disruption of trophic control [3,4]. In aquatic systems, the size-selective nature of many fisheries has led to the disproportionate removal of larger-bodied fishes [5] and declines in body size of entire predator guilds [6].…”

Predators catalyze an increase in chloroviruses by foraging on the symbiotic hosts of zoochlorellae

“…The virus background death rate was set at 1.3 per day, which is the median of wintertime decay rates reported for a temperate chlorovirus (25). Other parameters were taken from literature compilations for protists and cyclops (10,11), with r = 2, k = 100, h = 0.0003, e = 0.01, d c = 0.1, and a = 50. The model was solved using the ode45 solver in Matlab.…”

“…The connection between the predator and virus production is through the overall foraging rate F, which is embedded in predator-prey models as the product of predator density and the per capita foraging rate, f pc , written as a type II functional response: f pc = aN=1 + ahN, where a is the area of capture (the space cleared of prey by a predator per unit time), h is the handling time, and N is the prey density. We parameterized the model using data from a literature compilation describing the interactions between cyclops and various protists (10,11) to predict the size and timing of virus blooms that would arise through the predator-activated mechanism. Model solutions suggest typical predator-prey cycles (Fig.…”