SAFFO, M.B.: Symbiosis: a Complex and Delicate Balance

Symbiotic associations are intimate associations among two or more species. Such interspecific intimacy can have diverse evolutionary outcomes, ranging from antagonistic interactions (parasitisms and pathogenic associations) to mutualistic ones. Even when well understood (and many are not), the dynamics of many symbiotic associations resist simple definition. Many multi-partner symbioses embrace both antagonistic and mutualistic species interactions within a single association.Many others vary in their effects over time and space, depending on the particular environmental conditions, developmental stages, and species partners involved; such examples suggest that the boundary between antagonistic and mutualistic symbiosis can be a thin and variable one. Recent symbiosis research, particularly on mycorrhizae and coral-dinoflagellate symbioses, but also on numerous other systems, has revealed, with compelling and instructive detail, the depth and extent of the ecological and evolutionary complexities of symbiont interactions in both plant and animal hosts. Ongoing investigations also continue to confirm the geographical and taxonomic ubiquity, and ecological and evolutionary (including agricultural and medical) importance of both parasitic and mutualistic symbioses. Drawing on symbiosis research on plant and animal (as well as computer) hosts, from marine, freshwater and terrestrial habitats, and on integration of molecular, ecological and systematic approaches, this symposium seeks to explore the commonalities between parasitic and mutualistic symbioses, and also to gather fresh insights from exploration of their differences.