A Theoretical Framework for Trait-Based Eco-Evolutionary Dynamics: Population Structure, Intraspecific Variation, and Community Assembly

Abstract

To understand how functional traits shape ecological communities it is necessary to understand both how traits across the community affect its functioning and how eco-evolutionary dynamics within the community change the traits over time. Of particular interest are so-called evolutionarily stable communities (ESCs), since these are the end points of eco-evolutionary dynamics and can persist over long time scales. One theoretical framework that has successfully been used for assembling ESCs is adaptive dynamics. However, this framework cannot account for intraspecific variationneither locally nor across structured populations. On the other hand, in moment-based approaches, intraspecific variation is accommodated, but community assembly has been neglected. This is unfortunate as some questions regarding for example local adaptation vis-a-vis diversification into multiple species requires both facets. In this paper we develop a general theoretical framework that bridges the gap between these two approaches. We showcase how ESCs can be assembled using the framework, and illustrate various aspects of the framework using two simple models of resource competition. We believe this unifying framework could be of great use to address questions regarding the role of functional traits in communities where population structure, intraspecific variation, and eco-evolutionary dynamics are all important. 1 .

Extending eco-evolutionary theory with oligomorphic dynamics

“…As in AD and QG, OMD can be extended to take into account class structure (Lion et al, 2022;Wickman et al, 2022) and the joint evolution of multiple quantitative traits (Sasaki et al, 2022). Class structure is a major feature of natural biological populations, taking into account individual differences in state including age, spatial location, infection or physiological status, and species.…”

“…Class structure is a major feature of natural biological populations, taking into account individual differences in state including age, spatial location, infection or physiological status, and species. By deriving equations for the frequencies and moments of the morph distributions in each class, it is possible to apply OMD to a broad range of realistic ecological scenarios (Lion et al, 2022; Wickman et al, 2022). Furthermore, Lion et al (2022) show how the theory of reproductive values can be used to obtain compact analytical expressions for the dynamics of multimodal trait distributions in structured populations under density- and frequency-dependent selection.…”

“…The second term between brackets is scaled by the morph variances and therefore corresponds to a second-order correction. It captures the decrease in the mean growth rate due to individual phenotypic deviations from the mean trait, known as the “genetic (or standing) load” in the QG literature (Lande & Shannon, 1996; Kirkpatrick & Barton, 1997; Chevin, 2013; Wickman et al, 2022). In equation (8), the genetic load is a multi-morph extension of these previous results and takes the form of an average, over all morphs, of the strength of stabilising or disruptive selection around the morph mean (given by the curvature of the fitness function r ( z )), weighted by the morph genetic variance.…”

“…As in AD and QG, OMD can be extended to take into account class structure (Lion et al, 2022; Wickman et al, 2022) and the joint evolution of multiple quantitative traits (Sasaki et al, 2022).…”

“…The approach we describe here uses an "oligomorphic" approximation introduced by Sasaki & Dieckmann (2011), and is related to various trait-based approaches developed in community ecology and quantitative genetics (Wirtz & Eckhardt, 1996;Norberg et al, 2001;Débarre et al, 2013Débarre et al, , 2014Barabás & D'Andrea, 2016;Débarre & Otto, 2016;Klauschies et al, 2018;Mullon & Lehmann, 2019;Barabás et al, 2022;Wickman et al, 2022). This new theoretical framework explicitly takes into account the effect of environmental feedback, notably frequency-and density-dependent selection, on the joint dynamics of ecological variables and trait distributions, and has the potential to facilitate a tighter integration between eco-evolutionary theory and empirical data.…”