Introduction

The overarching goal of community ecology is to address broad problems, from predicting the effects of species’ invasion and loss to understanding the processes affecting the diversity, resilience and robustness of ecological systems. Ecological theory addresses these questions through the development of models that examine how species interact within food webs, and how those interactions give rise to the community-level properties we observe in natural systems, such as the relationship between complexity and stability, and the distribution of links across the food web. We argue here that current theory in community ecology is limited in its ability to address these fundamental questions, because it has largely ignored the role of species to modify their traits in response to their environment. This oversight is especially evident from the paucity of theory that considers how the broad problems outlined above are affected by the ubiquitous ability of prey to modify their traits to balance the trade-off between foraging gain and predation risk (Lima and Dill 1990; Lima 1998; Werner and Peacor 2003).

The traditional approach to community ecology is focused largely on linked pairwise interactions between populations, whether through competition, exploitation, or mutualism (May 1973; Pimm 1982; Bender et al. 1984; Yodzis 1988; Schoener 1993). These pairwise interactions are treated as building blocks upon which our understanding of larger ecological communities can be built, with the implicit assumption that pairwise interactions are independent of the ecological context in which they are embedded (Wootton 1994; Abrams 1995; Werner and Peacor 2003). A critical evaluation of this assumption began to emerge in the late 1960s. Vandermeer (1969) introduced the notion of ‘higher-order interactions’ (HOIs) wherein the interaction between two species is modified by other species in the system. While early attempts to test for HOIs were equivocal (Wilbur 1972; Neill 1974; Werner and Peacor 2003), the idea that species’ interactions were not fixed began to gain wider acceptance through the development of foraging theory in the 1970s and 1980s.