The Definition and Interpretation of Guild Structure in Ecological Communities

Abstract

(1) The species guild is frequently cited as an ecological entity but lacks any formal or testable definition. Psychophysical unfolding theory is employed to define a testable model of guild structure using data derived from a community matrix. The model presents structure visually and may be more biologically realistic than other related models. Relevant assumptions are outlined and discussed. (2) The technique was applied in detail to data for four groups of predatory invertebrates (freshwater triclads, woodland opilionids, field layer spiders and coral reef gastropods) and produced statistically significant results. The dimensions created, linking predators and resources, are interpreted in terms of the original data. As well as determining the existence of guilds the visual models facilitate unique comparisons between communities which appear to have similar structures despite their diverse origins. (3) Unfolding analysis was applied to a further range of groups reported or expected to form guilds. A high rate of positive results suggests that a consensus exists about guild constitution. Some major divergences from this consensus are also indicated. The general significance of unfolding analysis is discussed. The models may have further relevance to the species analysed where they can lead to testable hypotheses. These hypotheses should require information not used in constructing the model to increase the objectivity of the exercise.