Symbiosis: cooperation, slavery or domestication?

Douglas, A. E.
University of York, York, UK

Lichens are symbioses, intimate associations between phylogenetically-distant organisms. The purpose of my talk is to explore the essential features of symbioses, using a range of associations of animal, plant and fungal hosts with microorganisms as examples. A fundamental issue is whether a symbiosis is a relationship shaped by reciprocal cooperation between equal partners or a relationship between a controlling host partner and its microbial slaves or domesticates. I will describe empirical evidence for both cooperation and host-mediated control. Further information on the balance of power between the host and microorganisms can be gleaned from the evolutionary consequences of modes of transmission (vertical or horizontal) and from analysis of the susceptibility of symbioses to collapse in response to environmental stress.