Figure 2: Host survival for coevolving sympatric and allopatric pairs of worms and E. faecalis . Microbe-mediated protection was assessed for (A) sympatric pairs of coevolved worms and E. faecalis, (B) allopatric pairs of evolved worms and ancestral E. faecalis , and (C) allopatric pairs of ancestral worms and evolvedE. faecalis . Bigger symbols represent mean ± S.E. and consists of six biological replicates and four technical replicates. Smaller symbols indicate the data distribution. Circles indicate sympatric pairs of coevolved E. faecalis and worms, squares indicate ancestral pairs of E. faecalis and worms and triangles indicate allopatric pairs of E. faecalis and worms. Letters indicate results of a GLMM, followed by a Tukey Post-hoc Test. The same letter indicates no significant difference. Axis scales were chosen to be the same across all plots.
Infection with S. aureus over evolutionary time in the experiment led to the substantial enhancement of microbe-mediated protection, with the evolutionary background of the sympatric pair of host and E. faecalis having a significant impact on host survival (Mixed Effects Model, X2=42.479, df=4, p<0.001; Figure 2A). Higher microbe-mediated protection in comparison to the Ancestor occurred in all evolutionary histories involving pathogen presence across the temporal heterogeneity treatments in our evolution experiment (Always, 2.1. and 5.1.). However, this did not occur in the pathogen absence (Never) treatment. Host evolutionary history alone had a significant effect on host survival (Mixed Effects Model, X2=35.779, df=5, p<0.001; Figure 2B), but did not reveal the same pattern as for sympatric pairs. No effect of bacteria evolutionary history alone on infected host survival was observed (Mixed Effects Model, X2=3.2511, df=5, p=0.6613; Figure 2C). Taken together, enhanced microbe-mediated protection evolved only as a product of coevolution and pathogen presence for sympatric pairs; this occurred regardless of the temporal heterogeneity.