Séminaires

Evolution of multiple infections with vertically transmitted symbionts

Associations between prokaryotic and eukaryotic individuals are widespread in nature and range from parasitism to mutualism. Frequently, several microorganisms simultaneously co-exist within a single host. Within-host interactions affect the dynamics of the symbiotic population and therefore the co-evolution with the host. Co-infections in horizontally-transmitted symbionts have held most of attention of theorists and empirists, who have focused on competitive interactions between these parasites, whereas vertically-transmitted symbionts were little studied. For a long time, multiple infections with such microorganisms were thought to be rare because the bottleneck occurring at each generation during the colonisation of the oocytes leads to the genetic homogenisation of the symbiotic population. To address these questions, we focus on two types of multiple infections in arthropods, one involving closely related symbionts (several strains that belong to the same bacterial genus), the other involving symbionts with lower relatedness (several bacterial species).