Population structure reduces benefits from partner choice in mutualistic symbiosis

Abstract

Mutualistic symbioses are key drivers of evolutionary and ecological processes. Understanding how different species can evolve to interact in mutually beneficial ways is an important goal of evolutionary theory, especially when the benefits require costly investments by the partners. For such costly investments to evolve, some sort of fitness feedback mechanism must exist that more than recoups the direct costs. Several such feedback mechanisms have been explored both theoretically and empirically, yet we know relatively little of how they might act together, as they probably do in nature. In this paper, I model the joint action of three of the main mechanisms that can maintain interspecific cooperation in symbioses: partner choice by hosts, population structure amongst symbionts and undirected rewards from hosts to symbionts. The model shows that population structure reduces the benefit from partner choice to hosts. It may help or hinder beneficial symbionts and create positive or negative frequency dependence depending on the nature of host rewards to the symbiont. Strong population structure also makes it less likely that host choosiness and symbiont cooperation will be jointly maintained in a population. The intuition behind these results is that all else being equal, population structure reduces local variation available to the host to choose from. Thus, population structure is not always beneficial for the evolution of cooperation between species. These results also underscore the need to do full analyses of multiple mechanisms of social evolution to uncover the interactions between them.

Eco-evolutionary dynamics in metacommunities: ecological inheritance, helping within- and harming between-species

“…In other words, inter-temporal effects emerge because individuals inherit not only their genes, but also an ecological environment that has been transformed by their ancestors (Odling-Smee et al, 2003, Bonduriansky, 2012. By considering the effects of such ecological inheritance on multi-species interactions, our model generalises previous models of local ecological interactions in the presence of relatives that ignored trait-induced changes in abundance, either altogether (Frank, 1994, Foster and Wenseleers, 2006, Wyatt et al, 2013, Akçay, 2017 or in the evolving species (Lehmann, 2008).…”

“…Our analysis thus makes the empirical prediction that antagonism is more likely when dispersal is limited (Figure 7). Previous theory has focused on understanding how "altruism" or mutualism between species can evolve in the presence of relatives (Frank, 1994, Foster and Wenseleers, 2006, Wyatt et al, 2013, Akçay, 2017. These studies have highlighted that the evolution of mutualism is facilitated by among-species genetic correlations, which emerge when dispersal is limited.…”

“…By considering the effects of such ecological inheritance on multi-species interactions, our model generalises previous models of two-species evolution in the presence of relatives that ignored trait-induced demographic changes, either altogether (Frank, 1994, Foster and Wenseleers, 2006, Wyatt et al, 2013, Akçay, 2017 or in the evolving species (Lehmann, 2008).…”

Collapse and rescue of cooperation in evolving dynamic networks

“…These pathways include population structure [1], phenotypic feedbacks [2,3], payoff synergies [4], partner choice [5], among others [e.g., see reviews in [6][7][8]. When operating together, these pathways to cooperation can reinforce [6,[9][10][11] or counteract each other [12]. This extensive literature overwhelmingly tries to explain how cooperation can persist in the face of conflicts of interests.…”

No selection for cheating in a natural meta‐population of rhizobia

“…e,f ) . This suggests that plants ‘choose’ rhizobia genotypes in the wild, or that natural rhizobia populations are spatially structured (Akçay, ).…”