The Community Concept

For almost as long as ecology has been a discipline, it has struggled to define what constitutes an ecological community. A sharp dichotomy emerged early on, contrasting the view that communities were tightly integrated entities consisting of interdependent species (the community-unit concept) vs. the view that species co-occur largely according to the individualistic response of each species to spatially variable environmental conditions (the individualistic concept). To a large degree, the latter view has dominated ecological thought since the mid-20th century, based to a considerable extent on empirical patterns of community composition along environmental gradients. However, it has been repeatedly pointed out that neither view (in its extreme form) can capture the reality of processes and patterns in real communities, in which species often show both some degree of interdependence and gradual change in composition based on environmental conditions. Despite the debate regarding the concept of an ecological community, the discipline of community ecology has thrived and remained a key pillar of the broader field of ecology, with intense debates over the importance of competition in driving community structure and the relative importance of processes occurring at different spatial and temporal scales, among others. Finally, while few contemporary theoretical ecologists treat communities as belonging to discrete types, the community-unit concept lives on in applied ecology, where the classification of communities (often described as “vegetation” or “ecosystem”) is commonplace in order to facilitate conservation management, prioritization, and policy.