The Patch Dynamics Concept of Stream Community Ecology

Stream ecologists are faced with the problem of recognizing patterns in community organization and explaining the processes that determine these patterns. I argue that streams conform reasonably closely to the patch dynamics explanation of community organization which emphasizes temporal phenomena and focusses on the importance of history and chance. Even where competition or predation have been shown to play a role in shaping stream communities, the temporal phenomena of disturbance and colonization are invariably also of fundamental importance. In most cases, temporal variation is probably the factor of overriding significance, and species with weedy characteristics are a particularly prominent feature of streams. I highlight the critical role played by refugia as sources of recolonization after spates, and therefore as buffers against disturbance. A theoretical framework based on the patch dynamics view of community ecology may provide a unifying theme in stream ecology.