Abstracts (first author)
Dynamics of protective symbiosisPDF
Symbiosis, in which different species engage in prolonged and intimate associations, is gaining recognition as a ubiquitous feature of animal life. In many species, associations with symbiotic microorganisms are pervasive. These microbial associates are often heritable, transmitted with high fidelity from parent to offspring. Because host species and their symbionts share fates, inherited symbionts may exert beneficial effects on the hosts like conferring protection against adverse conditions. Among insects, aphids represent the best-studied case of protective symbioses. These sap-feeding insects may harbour one or several heritable bacterial symbionts, some of them providing protection against various natural enemies. To understand the dynamics of these protective symbioses in host populations, two barriers have to be investigated: the ability of microbial symbionts to infect a new host individual and the maintenance of symbionts infection over host generations. Aphids' biotic environment includes both the plants they feed on and the natural enemies they encounter (predators and parasitoids). Aphid individuals harbouring or not protective symbionts may co-occur on common plants, and horizontal transfers (transmission between host individuals) could potentially occur through direct contacts between aphids and/or the shared plant. Once present in a host population, the maintenance of protective symbionts depends on costs and benefits associated with such a symbiosis. In nature, selection pressures exerted by natural enemies may strongly fluctuate. By affecting host’s ecology through protective phenotype, the evolutionary relationship between a host and its protective symbionts would therefore be temporally and spatially dynamic. Horizontal transmission of protective symbionts and their maintenance in host populations, studied by various empirical approaches, will be presented to contribute to our understanding of symbionts’ dynamics in natural host populations.