Modeling the continua in the outcomes of biotic interactions

Abstract

The outcome of many ecological interactions lies somewhere along a continuum between pure positive and pure negative effects. Although the popularity of this idea has notoriously risen in the last decades, with the occurrence of continua in interaction outcomes invoked for a wide variety of interactions, the absence of a precise theoretical treatment has led to considerable inaccuracy and ambiguity in its treatment. We develop here a consumer‐resource model to explore the occurrence of continua. This model is based on the assumption that the distribution of individual interaction events includes both negative and positive immediate outcomes, with variable frequencies, for at least one of the interacting species. Our study shows that continua in interaction outcomes happen just by varying the sign and impact of individual events. The exact shape of the continua depends on the proportion of positive versus negative events and the relative magnitude of per‐capita interaction strengths. Our model shows that continua in interaction outcomes are a key property of most pairwise interactions and are originated from the variable roles played by the interacting partners. It constitutes a step forward in the paradigm change from discrete categorization of ecological interactions to a new perspective over a continuous space.

Dual species interaction and ecological community stability

“…I extend a recent theoretical framework of population dynamics with dual interaction (Gómez et al, 2023) into more complex systems. The previous work (Gómez et al, 2023) proposed a simple two‐species interaction model (extended from a classical consumer–resource model) with negative and positive terms in each equation (dual interaction).…”

“…I extend a recent theoretical framework of population dynamics with dual interaction (Gómez et al, 2023) into more complex systems. The previous work (Gómez et al, 2023) proposed a simple two‐species interaction model (extended from a classical consumer–resource model) with negative and positive terms in each equation (dual interaction). The key finding is that interaction outcomes or signs can change even in the same ecological context, suggesting an essential role in the continuity of ecological interaction outcomes for community dynamics (Gómez et al, 2023).…”

“…Most species interactions are inherently not singular but rather can have different simultaneous (“dual”) types of outcomes via multiple mechanisms (Gómez et al, 2023). A recent featured concept is context dependence, in which interaction outcomes (types of singular interactions) change depending on the variation in several factors, including abiotic and biotic environments (Butterfield & Callaway, 2013; Frederickson, 2017; Hoeksema et al, 2010).…”

“…Even within a context, variation of interaction outcomes can happen, depending on intraspecific variations such as age, size, phenotype, and genotype (Thompson, 1988, 2005, 2013). The variation of interaction outcomes can cause the coexistence of negative and positive immediate effects for at least one of the interacting species (“dual interaction”) (Gómez et al, 2023). In plant–rhizosphere mutualistic systems, plant individuals associate with multiple microbial genotypes.…”

Granivore abundance shapes mutualism quality in plant–scatterhoarder interactions

“…Mathematical modeling offers a solution to this challenge (e.g. Holland & DeAngelis, 2010; Cao et al ., 2022; Gómez et al ., 2023), but it has been underutilized in this domain.…”