Consumer–resource Body-Size Relationships in Natural Food Webs

Abstract

It has been suggested that differences in body size between consumer and resource species may have important implications for interaction strengths, population dynamics, and eventually food web structure, function, and evolution. Still, the general distribution of consumer-resource body-size ratios in real ecosystems, and whether they vary systematically among habitats or broad taxonomic groups, is poorly understood. Using a unique global database on consumer and resource body sizes, we show that the mean body-size ratios of aquatic herbivorous and detritivorous consumers are several orders of magnitude larger than those of carnivorous predators. Carnivorous predator-prey body-size ratios vary across different habitats and predator and prey types (invertebrates, ectotherm, and endotherm vertebrates). Predator-prey body-size ratios are on average significantly higher (1) in freshwater habitats than in marine or terrestrial habitats, (2) for vertebrate than for invertebrate predators, and (3) for invertebrate than for ectotherm vertebrate prey. If recent studies that relate body-size ratios to interaction strengths are general, our results suggest that mean consumer-resource interaction strengths may vary systematically across different habitat categories and consumer types.

Prohibition rules for three-node substructures in ordered food webs with cannibalistic species

“…These differences might indicate that in terrestrial ecosystems body mass is not as important for generating feeding hierarchies as it is in lake ecosystems. In Brose et al (2006) similar results have been found and it was hypothesised that this is due to physical and morphological constraints on trophic interactions. For example, if a lack of hard surfaces (as in pelagic systems) requires predators to consume their prey in one piece, gape limitation determines the maximal prey size.…”

“…If this one-dimensional niche space is anisotropic, species with a high position on the niche axis feed on those with a low position with a different probability than vice versa. Since in food webs it has been reported that predators are commonly larger than their prey (at least when parasites are excluded), body mass is indeed a useful proxy for niche position (Brose et al 2006).…”

Functional traits determine heterospecific use of risk‐related social information in forest birds of tropical South‐East Asia

“…Therefore, the aspect of prey vulnerability most directly relevant to our study should concern the identity of predators the prey are vulnerable to, and therefore most likely to mob, rather than the modes of predator–prey interactions such as predator detection and escape, to which traits such as foraging technique and predator detection/escape strategy would have been more relevant (Lima, 1993; Sridhar et al., 2012). Functionally, body size fundamentally defines whether a species can be caught, subdued, and consumed by a given predator species (Brose et al., 2006; Cohen et al., 1993; Templeton et al., 2005), while foraging height determines the spatial overlap between prey and potential predators and thus prey exposure to and likelihood of encountering predators in forest ecosystems. These two traits thus represent the most relevant functional traits to the ecological context concerned in our study.…”

The signature of phylogenetic constraints on food-web structure

“…Second, we investigate how phylogeny can affect the relationship between consumer and resource body masses. In a recent paper, Brose et al (2006b) used a large data set and showed that the consumer body mass scales with resource body mass following a power law with an exponent significantly larger than one. This indicates that the gap between consumers' and resources' masses increases with body size.…”