Résumé
Most of the evidence for a key role of parasites in structuring communities is based on the idea of a dierential susceptibilityof host species to infection and its consequences. Recent advances in community ecology suggest that life-history traits of free-living species can be an important determinant of their co-existence within communities. On the other hand, parasites have thepotential to indirectly alter the life-history traits of their hosts, such as developmental time or dispersal. We discuss the idea thatthese indirect eects could inØuence the structure of free-living and parasite communities. We explore this idea in relation torelated concepts including `parasitic arbitration' and engineering processes.