Extending the gleaner–opportunist trade‐off

Abstract

1. Species exhibit various trade-offs that can result in stable coexistence of competitors. The gleaner-opportunist trade-off to fluctuations in resource abundance is one of the most intuitive, yet also misunderstood, coexistence-promoting tradeoffs. Here, we review its history as an ecological concept, discuss extensions to the classical theory and outline opportunities to advance its understanding.2. The mechanism of coexistence between species that grow relatively faster than their competitors in a low-resource environment (i.e. a gleaner) versus a highresource environment (i.e. an opportunist) was first proposed in the 1970s. Stable coexistence could emerge between gleaners and opportunists if the opportunist species (dominant in unstable environments) dampens resource fluctuations via relatively convex functional responses, while the gleaner species (dominant in stable environments) promotes fluctuations, or diminishes them less than the opportunist does, via relatively saturating functional responses. 3. This fluctuation-dependent coexistence mechanism has since been referred to by various names, including the Armstrong-McGehee mechanism and relative nonlinearity of competition. Several researchers have argued this mechanism likely plays a relatively minor role in species coexistence owing in part to the restricted range of conditions that allow it to operate. More recent theoretical research, however, suggests that relative nonlinearity can operate over wider conditions than previously thought.4. Here, we identify several novel, or little explored, extensions to the gleaneropportunist trade-off that can yield species coexistence under phenomena as diverse as fluctuations in predation/pathogen pressure, multiple resources, phenotypic plasticity and rapid evolution, amongst other phenomena.5. While the original definition of the gleaner-opportunist trade-off may be imperfect as a collective for these extensions, we argue that a subtle reframing of the trade-off focusing on species' performance in equilibrium versus fluctuating conditions (irrespective of preferences for high or low resources, predation pressure or other competitive factors) reveals their fundamental commonality in stable coexistence via relative nonlinearity. An extended framing shines a light on the potential ubiquity of this canonical trade-off in nature and on the breadth of theoretical and empirical terrain that remains to be trodden.

A test of the gleaner-opportunist trade-off among photosynthetic traits in Cryptophyte algae

“…We took a novel approach to evaluate the potential origin of this type of trade-off through evolutionary diversification of the traits themselves by using phylogenetic comparative methods to control for the evolutionary history of our focal species. As we did not find a gleaner-opportunist trade-off between photosynthetic traits our work supports the view that this trade-off may not be as widespread as previously assumed (Litchman et al, 2007; Isanta-Navarro et al, 2022; Yamamichi & Letten, 2022).…”

“…Gleaner-opportunist trade-offs are believed to be important in the maintenance of diversity in ecological communities (Litchman et al, 2007; Yamamichi & Letten, 2022). The underlying assumption is that this trade-off allows for the coexistence of multiple species when they are competing for a variable resource.…”

A Mechanistically Integrated Model of Exploitative and Interference Competition over a Single Resource Produces Widespread Coexistence

“…For a replicating rather than a spontaneously generated resource, this allows the possibility of stable limit cycles. When different non-linear function responses (for example, when 𝜏 1 ≠ 𝜏 2 ) result in a trade-off between fitness in low-resource environments (gleaners) and high-resource environments (opportunists), resource oscillations may contribute to species coexistence (Armstrong andMcGehee 1980, Yamamichi andLetten 2022). The interplay of this effect with interference competition is beyond the scope of our study.…”

Eco‐evolutionary maintenance of diversity in fluctuating environments

“…More recently, an increasing number of empirical studies have demonstrated that temporally fluctuating selection/environments are important in maintaining both genetic variation (Bergland et al, 2014; Machado et al, 2021; Rudman et al, 2022; Yi & Dean, 2013) and species diversity (Angert et al, 2009; Ellner et al, 2019; Hallett et al, 2019; Letten et al, 2018; Sommer, 1985; Zepeda & Martorell, 2019). Although the topic itself has a long history in ecology (reviewed in Barabás et al, 2018; Chesson, 2000b; Ellner et al, 2019; Stump & Vasseur, 2023; Yamamichi & Letten, 2022)and evolutionary biology (reviewed in Felsenstein, 1976; Frank, 2011; Gillespie, 1991; Hedrick, 1986; Hedrick, 2006; Hedrick et al, 1976; Johnson et al, 2023: see also Figure 1 and Figure S1), the recent accumulation of empirical evidence has coincided with renewed theoretical interest into the role of temporally fluctuating environments in maintaining genetic variation (Bertram & Masel, 2019b; Dean, 2018; Dean et al, 2017; Gulisija et al, 2016; Kim, 2023; Novak & Barton, 2017; Park & Kim, 2019; Schreiber, 2020; Svardal et al, 2015; Wittmann et al, 2017, 2023; Yamamichi et al, 2019; Yamamichi & Hoso, 2017) and species diversity (Barabás et al, 2018; Chesson, 2018; Ellner et al, 2019; Fung et al, 2022; Johnson & Hastings, 2022a, 2022b; Meyer et al, 2022; Pande et al, 2020; Schreiber, 2021, 2022; Schreiber et al, 2019).…”