The body-size dependence of mutual interference

Abstract

The parameters that drive population dynamics typically show a relationship with body size. By contrast, there is no theoretical or empirical support for a body-size dependence of mutual interference, which links foraging rates to consumer density. Here, I develop a model to predict that interference may be positively or negatively related to body size depending on how resource body size scales with consumer body size. Over a wide range of body sizes, however, the model predicts that interference will be body-size independent. This prediction was supported by a new dataset on interference and consumer body size. The stabilizing effect of intermediate interference therefore appears to be roughly constant across size, while the effect of body size on population dynamics is mediated through other parameters.

Temperature alters food web body-size structure

“…The ratio of predator body size to prey body size affects predator-prey dynamics [6,7], interaction strengths [8,9], trophic position [8,10] and the size structure and function of food webs [11]. Because of this, body size is increasingly recognized as a factor influencing species persistence and the stability of complex food webs [8,12,13].…”

Quantifying predator dependence in the functional response of generalist predators

“…It does, however, indicate that predator dependence as encapsulated by Beddington–DeAngelis model characterizes N. ostrina 's feeding rates the best among the models we considered, and that its effects are discernible over the species abundances and diversity of prey that this generalist predator experiences in the field. The poorer performance of the Hassell–Varley model implies that Nucella 's mutual predator effects result from individuals altering each other's available prey search time rather than search efficiency (DeLong ). More generally, the nature of predator dependence was far from ratio dependent.…”

“…While further studies involving generalist predators will be needed to determine how diet breadth itself can affect the strength of predator dependence, a likely feature distinguishing the functional responses of generalist and specialist predators is the variable propensity of a generalist's different prey species to elicit predator dependence. For example, rates of predator interference are expected to depend on the relative velocities with which predators and prey move, hence should differ for mobile and sessile prey species (DeLong ). For the whelks of our study in particular, predator dependence will have been driven by a number of mechanisms that vary by prey identity and differ in their qualitative nature even for similarly (im)mobile prey.…”

“…4c). Future experiments manipulating community structure directly will be needed to determine whether such prey‐specific influences of community structure tend to be idiosyncratic or conform to useful categorisations (see also DeLong ).…”

Individual Variation Decreases Interference Competition but Increases Species Persistence

“…However, the ability to reduce resource density and persist may depend upon the factors controlling interaction strengths and consumer-resource interactions. A number of these factors have received a lot of attention, including foraging behaviour (Abrams and Matsuda, 2004;Schmitz et al, 1997), consumer and resource body sizes (VucicPestic et al, 2010) and relative velocities (DeLong, 2014;Pawar et al, 2012), prey defence mechanisms (Hammill et al, 2010;Yoshida et al, 2004), and environmental temperature (Dell et al, 2014;Gibert and DeLong, 2014;O'Connor, 2009). And while all these factors are important, the underlying assumption in ecology has historically been that populations are homogeneous collections of individuals and that mean trait values are sufficient for understanding ecological processes (Lomnicki, 1988).…”