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Evolutionary branching of parasites in a periodic environment. Agricultural ecosystems as an example.

Le : 12/11/2010 10h30
Par : Frédéric Hamelin (Agrocampus Ouest Rennes)
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Résumé : We are interested in the evolutionary epidemiology of crop plant parasites. Their peculiarity is to face abrupt changes in host density due to planting and harvesting, as periodic events. The associated models thus combine continous (epidemiological) and discrete (host population) dynamics. This is termed `semi-discrete' modelling in the Mathematical Biology literature. Performing an `evolutionary invasion analysis' (sensu Adaptative Dynamics theory), we show that evolutionary branching of the parasite phenotype can occur, assuming there is a trade-off between intra- and inter-season transmission abilities. Since there are experimental evidences for such a trade-off (e.g. in the take-all parasite of wheat), our model provides the ecological and phenotypical bases for the coexistence of genetically distinct subgroups in the parasite population (as observed in e.g. the take-all of wheat also). We discuss why this evolutionary insight was not captured in previous and recent research. (This is a joint work with Magda Castel, Sylvain Poggi and Ludovic Mailleret.)