Session: Social microbes (Mitri, Dupré, Clarke, Birch)

Microbes, especially but not exclusively bacteria, frequently exist in closely integrated consortia including multiple types of cell. Indeed multispecies communities are the dominant living systems on Earth, and it is such systems that are typically exposed to natural selection as an integrated unit. This implies, contrary to very widespread assumptions about evolution, that entities that compose lineages are distinct form the entities that are exposed to selection. This paper will explore some of the consequences of this situation for our understanding of evolution, especially the evolution of cooperation.