Antagonistic Coevolution Limits the Range of Host Defense in C. elegans Populations

Jordan A Lewis,Sebastián Durán Ahumada,Levi T Morran,Hannan Sylla,Mckenna J Penley

doi:10.3389/fcimb.2022.758745

Jordan A Lewis, Sebastián Durán Ahumada + Show 3 more

Open Access

https://doi.org/10.3389/fcimb.2022.758745

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Abstract

Host populations often evolve defenses against parasites due to the significant fitness costs imposed by infection. However, adaptation to a specific parasite may alter the effectiveness of the host’s defenses in general. Consequently, the specificity of host defense may be influenced by a host population’s evolutionary history with parasites. Further, the degree of reciprocal change within an interaction may profoundly alter the range of host defense, given that antagonistic coevolutionary interactions are predicted to favor defense against specific parasite genotypes. Here, we examined the effect of host evolutionary history on host defense range by assessing the mortality rates of Caenorhabditis elegans host populations exposed to an array of Serratia marcescens bacterial parasite strains. Importantly, each of the host populations were derived from the same genetic background but have different experimental evolution histories with parasites. Each of these histories (exposure to either heat-killed, fixed genotype, or coevolving parasites) carries a different level of evolutionary reciprocity. Overall, we observed an effect of host evolutionary history in that previously coevolved host populations were generally the most susceptible to novel parasite strains. This data demonstrates that host evolutionary history can have a significant impact on host defense, and that host-parasite coevolution can increase host susceptibility to novel parasites.

Highlights

Parasites are ubiquitous in nature and are thought to be a key factor in the evolution and maintenance of genetic diversity within host populations (Hamilton, 1980; Anderson and May, 1982; Rainey et al, 2000; Thomson, 2009)
We first tested for the evolution of elevated host defense in our coevolved and one-sided host populations against the coevolved parasite populations derived from SM2170
We found that the coevolved hosts exhibited lower rates of mortality than the control hosts when exposed to the coevolved populations of SM2170 (Figure 2; x12 = 5.174, P =.023), indicating the coevolved hosts adapted to their respective antagonists during experimental coevolution

Summary

Introduction

Parasites are ubiquitous in nature and are thought to be a key factor in the evolution and maintenance of genetic diversity within host populations (Hamilton, 1980; Anderson and May, 1982; Rainey et al, 2000; Thomson, 2009). Natural observations have aligned with expectations, as hosts have evolved a multitude of strategies for defending against infection (Roy and Kirchner, 2000; Ellis, 2001; Lemaitre and Hoffmann, 2007; Diamond et al, 2009; Parker et al, 2011; War et al, 2012; De Roode et al, 2013; Weiss et al, 2014). Despite the benefit of evolved host defenses and the ubiquity of parasites, natural populations experience considerable variance in levels of host defense over space and time (Allen et al, 2004; Laine, 2004)

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