Ecological boundaries: a derivative of ecological entities
Defining ecological boundary as an outer envelope of an ecological entity such as an individual, colony, population, community, an ecosystem, or any other discernible unit provides methodological benefits and should thus enhance existing perspectives and research protocols. I argue that, because boundaries are features of entities, the first step in investigation of boundary structure and properties should involve identification of the entity the presumed boundary of interest belongs to. I use a general perspective where ecological systems are parts of a larger system and themselves are made of subsystems (or entities). Such a general hierarchy of ecological objects offers guidance as to how boundaries can be found for specific systems, and how their investigations might lead to reliable and generalizable insights. In particular, it may help in (a) categorizing types of boundaries based on mechanisms leading to formation of entities; (b) deciding what is and what is not a boundary by clarifying the nature of discontinuities seen in nature (e.g., sharp habitat transitions or weak separation of entities); (c) assisting in selecting fruitful resolution at which boundaries are examined; (d) approaching boundaries in complex, nested systems; and (e) deciding what criteria to use in answering questions about a particular boundary type. To facilitate the above I provide general criteria one may use for identifying ecological entities. Such criteria should assist in focusing on boundaries appropriate for a given research question. Finally, where advancing the theoretical framework for ecological boundaries is concerned, the diversity of boundary types will be better served when reorganized in relation to the concept of entity as discussed below.