Symbiosis

Abstract

Symbiosis—the close association of unlike organisms—was long considered a curiosity, interesting but confined to a small proportion of species in nature and of little consequence. But discoveries over the past 25 years have made it clear that symbiosis has shaped evolution and has affected all species and ecosystems. Symbiosis enabled plants to colonize land, termites to eat wood, and corals to build reefs. At the other end of the evolutionary timescale, symbioses arise constantly and can play an active role in the ecology of populations, giving plants and animals the ability to overcome disease, heat stress, and nutritional deficiencies. Human cells are themselves amalgamations of organisms with different evolutionary roots, and gut symbionts play a central role in human health. Drawing examples from diverse species and ecosystems, Nancy Moran explains the main drivers that fuel the origins of symbiotic unions as well as the obstacles to their stable persistence. The roles of symbioses in shaping Earth and life are explored, along with their potential as tools in efforts to reduce negative effects of global change.