Bacterial Community Dynamics

Abstract

The term community has been used in a number of different ways by ecologists (cf. Krebs, 1985; Diamond and Case, 1986). Indeed, Roughgarden and Diamond (1986) state that “... a natural unambiguous definition of communities does not exist.” They further state that the most inclusive definition of a community is “all the organisms in a prescribed area,” a definition that is usually restricted by the criteria used to describe the organisms and the boundaries delimiting the area (Roughgarden and Diamond, 1986). If we follow this definition, the set of organisms that we address is restricted to bacteria; the area to that of a leaf or leaflet. Because a leaf is discrete in space, the boundary of the community is explicitly delineated. Unlike many terrestrial habitats in which the “edge” of the area of interest may be more arbitrarily defined, the leaf margin clearly describes the edge of the phyllosphere habitat. However, each of the many plants in a canopy produces many leaves; each is, in turn, separated in space and inhabited by a distinct assemblage of bacteria (i.e., a community). In a canopy, there exists not a single habitat, but rather populations of habitats. Thus, bacterial communities in the phyllosphere are best described in terms of populations of communities on populations of leaves.