ALBERT

Description: Introduction Trophic interactions are one of the most important aspects shaping ecological communities, and the food-web paradigm has played a major role in the development of ecology as a science. Early food-web models attempted to simulate the flow of energy and biomass within local communities (Odum, 1956) or describe the structure of feeding relationships (Pimm, 1982). Species or “trophospecies” (i.e., groups of species that supposedly share the same sets of predators and prey; see Yodzis and Winemiller, 1999) have served as the building blocks of both types of trophic networks (usually referred to as flow webs and topological webs, respectively). Topological food webs are static “snapshots” lacking magnitudes (i.e., estimates of the rate of energy flow or the strength of trophic links) and therefore have limited utility for examination of ecological dynamics. The strength of trophic interactions can be estimated in different ways (e.g., observing magnitudes of biomass/energy transfers, modeling of consumer feeding preferences, functional responses or metabolic constraints, varying interaction coefficients in Lotka–Volterra multispecies competition models, and quantifying responses from manipulative field experiments; see Berlow et al., 2004, 2009). Food-web models have been used to predict risks of secondary extinction (Allesina and Bodini, 2004), examine consequences of biodiversity loss for ecosystem stability (McCann, 2000), and study direct and indirect effects of predators on prey populations (Bondavalli and Ulanowicz, 1999). Food-web models that lump individuals into species and trophospecies lose much valuable information concerning influential attributes associated with age, body size, foraging history, location, and reproductive tactics. Such lumping may inflate the number of trophic interactions associated with species or trophospecies and thus fails to take into account how variation in feeding preferences between individuals affects food-web structure and dynamics (Bolnick et al., 2007). Trait-based approaches have gained momentum in community and evolutionary ecology, and most ecologists now recognize the relevance of variation at intraspecific as well as interspecific levels (Bolnick et al., 2011). This recognition calls for exploration of new approaches to food-web ecology. Intraspecific trait variation can alter the number and strength of interspecific interactions, especially when food-web interactions are a function of body size (Otto et al., 2007; Berlow et al., 2009).