Abstracts (first author)
Experimental host-parasite coevolution in temporally variable environments
Antagonistic, host-parasite coevolution is predicted to be an important driver of genetic change. Despite this, few examples exist from natural populations, possibly because temporal environmental variation may interfere with the co-evolutionary process.
Here we investigate experimental co-evolution between Pseudomonas fluorescens and its phage SBW2Φ2 in a fluctuating temperature environment, changing between permissive (28ºC) and restrictive (32ºC) conditions, for phage populations. We investigated how the frequency of environmental change influenced coevolution in populations experiencing temperature switches every 2, 4 or 8 days, over a 16-day period. Phage persistence is severely reduced at 32ºC, thus we hypothesised that longer periods at 32ºC would be detrimental for the phage.
We found that coevolutionary dynamics under fine-grained fluctuations (every 2 or 4 days) did not differ from the constant 28ºC control. Contrary to expectation, coarse-grained fluctuations (every 8 days) benefited phage populations, despite extended periods at 32ºC. During periods of 32ºC, bacteria flourished in an environment where phage were unable to infect, but also lost previously acquired resistance. Although infections did not occur at 32ºC, all phage populations persisted. Accordingly, once populations were returned to 28ºC, phage benefitted from high infection rates of susceptible bacteria. Our results highlight the need to consider temporal environmental heterogeneity when investigating coevolutionary interactions.