A review of commensalism

The literature on commensalism was reviewed. Commensal associations have been found in many terrestrial and aquatic habitats. Early descriptions of commensalism limit the association to interactions providing commensals with unilateral feeding advantages. More recent discussions of commensalism suggest other benefits derived from the association. The commensal may derive protection, locomotion and improved reproduction from the association in addition to improved sources of nutrition. Commensalism is commonly described in footnotes to taxonomic descriptions of the species found in association. Often an association is classified as commensal with little criteria for making this distinction and with very little discussion of the natural history of the organisms in the association. Our knowledge of the natural history of commensal associations is limited. Discussions of the evolution of interspecific associations have produced several controversial hypotheses. The hypothesis that parasitism evolved first to commensalism and finally to mutualism seems most likely to be accurate. It is important to understand the nature of commensalism and its relationship to other interspecific associations. Knowledge of the benefits provided in commensalism may enable the researcher to more accurately determine the factors which contribute to the establishment of positive associations. Such knowledge may also aid in the development of new models for interspecific associations.