Resolving the roles of body size and species identity in driving functional diversity

Abstract

Efforts to characterize food webs have generated two influential approaches that reduce the complexity of natural communities. The traditional approach groups individuals based on their species identity, while recently developed approaches group individuals based on their body size. While each approach has provided important insights, they have largely been used in parallel in different systems. Consequently, it remains unclear how body size and species identity interact, hampering our ability to develop a more holistic framework that integrates both approaches. We address this conceptual gap by developing a framework which describes how both approaches are related to each other, revealing that both approaches share common but untested assumptions about how variation across size classes or species influences differences in ecological interactions among consumers. Using freshwater mesocosms with dragonfly larvae as predators, we then experimentally demonstrate that while body size strongly determined how predators affected communities, these size effects were species specific and frequently nonlinear, violating a key assumption underlying both size-and species-based approaches. Consequently, neither purely species-nor size-based approaches were adequate to predict functional differences among predators. Instead, functional differences emerged from the synergistic effects of body size and species identity. This clearly demonstrates the need to integrate size-and species-based approaches to predict functional diversity within communities.

Estimating the effects of non‐native species on nutrient recycling using species‐specific and general allometric models

“…Taxonomic identity contains no a priori information about the roles of individuals in ecosystems and must be coupled with some degree of trait information to make ecological predictions (Rafaelli, 2007;Rudolf, Rasmussen, Dibble, & Van Allen, 2014). In an attempt to forego the constraints of taxonomy researchers have proposed functional trait frameworks (McGill, Enquist, Weiher, & Westoby, 2006), and body size frameworks in particular (Brose et al, 2006;Woodward et al, 2005), to understand individual's roles in ecosystems.…”

Cannibalism and Intraguild Predation Community Dynamics: Coexistence, Competitive Exclusion, and the Loss of Alternative Stable States

“…For example, in many predatory species, individuals either switch resources or add resources to their diet as they develop (Werner and Gilliam 1984;Rudolf and Lafferty 2011;Rudolf et al 2014). Predator populations can thus be simultaneously regulated by stage-specific interactions with different species.…”

Relating trophic resources to community structure: a predictive index of food availability

“…Unfortunately, the various forms of trophic data reported among studies impede broad-scale comparisons because of different sampling methods, different trophic groups, incomplete sets of plant and animal taxa, and different units of measurements [8,9]. In the marine context, benthic and planktonic morphofunctional groups are often sampled with different instruments, on different surface areas or volumes, and among different habitats.…”