Evolution of spatially structured host–parasite interactions

Abstract

Spatial structure has dramatic effects on the demography and the evolution of species. A large variety of theoretical models have attempted to understand how local dispersal may shape the coevolution of interacting species such as host-parasite interactions. The lack of a unifying framework is a serious impediment for anyone willing to understand current theory. Here, we review previous theoretical studies in the light of a single epidemiological model that allows us to explore the effects of both host and parasite migration rates on the evolution and coevolution of various life-history traits. We discuss the impact of local dispersal on parasite virulence, various host defence strategies and local adaptation. Our analysis shows that evolutionary and coevolutionary outcomes crucially depend on the details of the host-parasite life cycle and on which life-history trait is involved in the interaction. We also discuss experimental studies that support the effects of spatial structure on the evolution of host-parasite interactions. This review highlights major similarities between some theoretical results, but it also reveals an important gap between evolutionary and coevolutionary models. We discuss possible ways to bridge this gap within a more unified framework that would reconcile spatial epidemiology, evolution and coevolution.

Immigration of susceptible hosts triggers the evolution of alternative parasite defence strategies

“…It is becoming increasingly clear that migration of hosts and parasites in spatially structured environments has important epidemiological and coevolutionary consequences [1,2], affecting, for example, host-parasite coexistence, local adaptation and coevolutionary dynamics [3][4][5]. Migration may also affect the type of host defence that is favoured by selection [6,7].…”

Spatial evolutionary epidemiology of spreading epidemics

“…This quasi-equilibrium captures the influence of kin competition between parasites and allows us to recover previous longterm predictions derived from classical invasion analyses [7,12,14]. When host population size is fixed, relatedness erodes the transmission benefit and the cost of virulence with equal weight.…”

“…Although we focus on two extreme cases of parasite dispersal (global versus local dispersal), a potential extension of our framework would be to consider more realistic dispersal kernels combining local and globaldispersal events (see, e.g. [7,12,14] for a review) or even study the joint evolution of dispersal with other pathogen life-history traits (e.g. [19]).…”

“…First, most theoretical studies focus on the long-term consequences of spatial structure on pathogen evolution using the adaptive dynamics framework [6][7][8][9][10][11][12]. These theoretical studies predict that, in a broad range of scenarios, lower migration selects for lower pathogen virulence (reviewed in [13,14]). Several experimental studies using microbial systems support this prediction [15][16][17].…”

Short Rotations in Forest Plantations Accelerate Virulence Evolution in Root-Rot Pathogenic Fungi

“…Moreover, the strong assumptions made on pathogen life-history are more often not relevant to tree pathogens emerging in a forest plantation. Besides, in a general way, directly transposing existing models, theory and results into different ecosystems that often constitute distinct complex systems remains a challenge [24][25][26]. Hence, there is a need for new simple models clearly focused on pathogens spreading in a forest plantation and using existing theory in evolutionary epidemiology to address practical questions.…”