Abstracts (first author)

Talk 

Experimental host-parasite coevolution in temporally variable environments

Author(s): Duncan AB, Jacob F, Dusi E, Hochberg M, Kaltz O

Summary:

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.



Abstracts (coauthor)

Summary:

Because host populations are generally sub-divided, the epidemiology of a parasite often depends on its ability to disperse among host sub-populations and successfully invade them. To investigate the factors that determine host-mediated parasite dispersal and its subsequent transmission we carried our microcosm experiments with the bacterial parasite Holospora undulata and its host, the fresh-water ciliate Paramecium caudatum. We found that (i) the dispersal of infected hosts largely depended on both host and parasite genotypes (but not their interaction), suggesting disease spatial dynamics varies with the genetic composition of local sub-populations. Besides, (ii) shortly after the arrival of infected hosts into a healthy population parasite success was determined by the genotype of the carrier hosts and its interactions with that of the parasite and the resident hosts. This further highlights the importance of host genotype for parasite dynamics among host sub-populations. (iii) After a couple of transmission cycles, parasite genotype, in combination with resident host genotype, gained influence, matching classical ideas of parasite transmission. It thus appears that different genetic factors play on parasite dispersal between groups of hosts, its short-term spread and longer-term establishment. This study also demonstrates the role of carrier host genotype for parasite dispersal and transmission among and within host sub-populations.

Contacts

Chairman: Octávio S. Paulo
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Address

XIV Congress of the European Society for Evolutionary Biology

Organization Team
Department of Animal Biology (DBA)
Faculty of Sciences of the University of Lisbon
P-1749-016 Lisbon
Portugal

Website

Computational Biology & Population Genomics Group 
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