Guilds, Functional Types and Ecological Groups

A wide range of terms such as 'guild' and 'functional type' have been used to describe groupings of species made on an ecological basis. However, such groupings have been based on a wide range of concepts and criteria, and there is no consistent association between the term used and the concepts and criteria intended. A classification of concepts is made, i.e. a classification of kinds of guild. A basic split is seen between Beta (environmental conditions) and Alpha (resource use) guild concepts. Species that are in the same Beta (environmental conditions) guild, prefer the same conditions and will tend to be found together. Species that are in the same Alpha (resource use) guild will not necessarily occur together; in fact, if the resource is limiting, competitive exclusion would tend to lead to their not being found together. The classification takes into account the intention and ecological concept behind the classification, and also the type of information and the method used to make the classification. As always in ecology, intermediates exist. Guilds are classified into five kinds of Beta guild and four kinds of Alpha guild: Beta guilds (based on distribution according to environmental conditions) based on observations of distribution: β1: Spatial distribution guilds. β2: Temporal distribution guilds. based on measurement of characters: descriptive characters: guilds formed subjectively: β3: Subjective beta character guilds. guilds formed objectively: β4: Objective beta character guilds. response to environmental factors: β5: Response guilds. Alpha guilds (based on resource type used, within communities): Rootian guilds, defined by characters intended to represent resource use: defined subjectively and not tested: α1: Subjective a priori Rootian guilds. defined subjectively, but tested objectively: α2: Tested a priori Rootian guilds. defined objectively: α3: Objective character Rootian guilds. defined by the behaviour of species: α4: Intrinsic guilds. For many existing guild classifications, it is unclear what concept the classification is based on, or how the methods used are related to the concept.