Trophic interaction modifications: an empirical and theoretical framework

Abstract

Consumer-resource interactions are often influenced by other species in the community. At present these 'trophic interaction modifications' are rarely included in ecological models despite demonstrations that they can drive system dynamics. Here, we advocate and extend an approach that has the potential to unite and represent this key group of non-trophic interactions by emphasising the change to trophic interactions induced by modifying species. We highlight the opportunities this approach brings in comparison to frameworks that coerce trophic interaction modifications into pairwise relationships. To establish common frames of reference and explore the value of the approach, we set out a range of metrics for the 'strength' of an interaction modification which incorporate increasing levels of contextual information about the system. Through demonstrations in three-species model systems, we establish that these metrics capture complimentary aspects of interaction modifications. We show how the approach can be used in a range of empirical contexts; we identify as specific gaps in current understanding experiments with multiple levels of modifier species and the distributions of modifications in networks. The trophic interaction modification approach we propose can motivate and unite empirical and theoretical studies of system dynamics, providing a route to confront ecological complexity.

Trait‐mediated indirect interactions: Moose browsing increases sawfly fecundity through plant‐induced responses

“…Trait‐mediated indirect interactions (defined by Abrams, ) are abundant in ecological systems, affecting various processes and interactions with implications for individual performance, population fluctuations, and community composition (Van Veen, Van Holland, & Godfray, ; Werner & Peacor, ). Their importance has received increasing attention, both theoretically (Golubski & Abrams, ; Terry, Morris, & Bonsall, ) and empirically (Ando, Utsumi, & Ohgushi, ; Nakamura, Miyamoto, & Ohgushi, ; Soler et al, ), but their effects are not yet fully understood. Trait‐mediated indirect interactions (from now “indirect interactions”) are particularly common in plant–herbivore communities, as plants are subjected to herbivory by several species of herbivores often without lethal consequences.…”

From apparent competition to facilitation: Impacts of consumer niche construction on the coexistence and stability of consumer‐resource communities

“…The explicit consideration of trophic interaction modifications has recently received increased attention (Terry, Morris, & Bonsall, and references within). In this line of work, our model investigates how positive niche construction effects interfere with apparent competition, to constrain species coexistence and community stability.…”

Interaction modifications lead to greater robustness than pairwise non‐trophic effects in food webs

“…There is a building appreciation that to improve our understanding of population dynamics within ecological communities, it is necessary to move beyond studies that focus on a single interaction process at a time (Kéfi et al, ; Levine, Bascompte, Adler, & Allesina, ). Trophic interaction modifications (TIMs) (Terry, Morris, & Bonsall, ; Wootton, ) occur when a consumer–resource interaction is modulated by additional species. These are a class of higher‐order processes since their effects are not fundamentally pairwise.…”