Ecology of Mutualisms

Abstract

Abstract Mutualisms are interactions among individuals of different species that benefit both sides and encompass a wide diversity of interspecific exchanges of resources or services. The effects of mutualisms pervade multiple levels of biological organisation. At the individual level, mutualisms provide fitness benefits for interacting partners, creating novel metabolic pathways and providing dispersal services, trophic rewards or defence against natural enemies. At the population level, the positive effects of mutualisms have the potential to increase population densities above the limits imposed by resource availability. At the community level, mutualisms form networks of interacting species that impact the persistence of local populations as well as their evolutionary and ecological dynamics. The broader implications of mutualisms to biodiversity are illustrated by the fact that mutualistic interactions are the backbone of species‐rich ecological communities, such as tropical rainforests and coral reefs, and by how mutualisms fueled the spreading of humankind around the world. Key Concepts Mutualisms are ecological interactions among individuals of different species that result in positive net benefits for both sides. Individuals of most species are involved in mutualistic interactions. The natural history of mutualisms is highly diverse, ranging from short‐term associations among partners to interactions in which individuals are biologically attached for most of their lives. Some mutualisms are symbiotic, that is, individuals show tight biological integration, but symbiosis and mutualisms are not synonyms. All animals, plants and fungi are built on mutualisms between eukaryote cells and intracellular symbionts that have became organelles, such as mitochondria and chloroplasts. Mutualisms have the potential to create positive feedbacks leading to large population densities, but these effects are offset by other ecological interactions, such as competition and predation, and also by the costs of mutualisms. Reciprocal specialisation is rare in species‐rich mutualisms. At the community level, mutualisms form multispecies ecological networks that show recurrent structural patterns. A variety of structural patterns observed in mutualistic networks have disparate effects on system dynamics, which can affect the long‐term persistence of species and communities. The most diverse ecosystems on Earth are shaped by mutualistic interactions.