Patchy indirect effects: how predators drive landscape heterogeneity and influence ecosystem dynamics via localized pathways

Abstract

Predators are widely recognized for their irreplaceable roles in regulating the abundance and altering the traits of lower trophic levels. Yet, predators also have irreplaceable roles in shaping community interactions and ecological processes in highly localized pathways, irrespective of their influence on prey density or behavior. We introduce a conceptual framework, patchy indirect effects, that outlines how predators indirectly affect other organisms via landscape patches. We focus on three main pathways and provide examples and detailed case studies herein: generating and distributing prey carcasses, creating biogeochemical hotspots by concentrating nutrients derived from prey, and killing ecosystem engineers that create patches. In each pathway, indirect effects of predation are localized within discrete areas with measurable spatial and temporal boundaries. Whereas density- and trait-mediated indirect effects function via population-scale changes, the patchy indirect effects concept outlines how predators drive landscape heterogeneity and influence ecosystem dynamics – including scavenger interactions, nutrient cycling, parasite/disease transmission risk, and local biodiversity – through pathways that function at individual- and patch-level scales. Our synthesis provides a more holistic view of the functional role of predation in ecosystems by addressing how predators create patchy landscapes via localized pathways, in addition to influencing the abundance and behavior of lower trophic levels.

Quality matters: stoichiometry of resources modulates spatial feedbacks in aquatic-terrestrial meta-ecosystems

“…Modelling studies on these active flows remain scarce despite their strong potential for understanding how herbivore movements and traits interact with predation (including non-consumptive effects, Schmitz et al, 2010) to determine the distribution of nutrients at the landscape scale (Anderson et al, 2010; Schmitz et al, 2018; Ferraro et al, 2022). This may provide emergent patterns, such as nutrient co-limitation induced by spatial processes (Marleau et al, 2015) or patchy distribution of resources (Johnson-Bice et al, 2022). In addition, we currently lack a clear understanding of the relative contribution of passive flows, which are associated to the entropy of a system (a current, an upwelling), and active vectors that can transport resources against entropy ( e.g., salmon swimming back up the river) across many ecotones (Schmitz et al, 2018; McInturf et al, 2019; Ellis-Soto et al, 2021).…”

Quality matters: Stoichiometry of resources modulates spatial feedbacks in aquatic‐terrestrial meta‐ecosystems

“…Modelling studies integrating such processes would help for instance understanding how animal foraging movements interact with predation avoidance to determine the distribution of nutrients at the landscape scale (Anderson et al, 2010; Ferraro et al, 2022; Schmitz et al, 2018). This may highlight further emergent patterns such as nutrient co‐limitation induced by spatial processes (Marleau et al, 2015) or patchy distribution of resources (Johnson‐Bice et al, 2022). Our study sets bases to understand fundamental mechanisms by which spatial flow stoichiometry modulates cross‐ecosystem interactions and the functioning of communities at different scales.…”