Modelling confinement experiments in community ecology: differential mobility among competitors

Field experiments in which mobile organisms are confined inside enclosures have been widely used in many areas of marine, freshwater and terrestrial e cology in the past three decades. Some ecologists believe that at least som e and possibly most, of the interpretation of this work may be subject to d ispute because of potential artefacts associated with the confinement itsel f. Simulations suggested that moderate or even severe artefacts may arise f rom using enclosures that are 'too small', which could produce inferential nonsense in some circumstances (Mac Nally, 1997). Here, the influence of di fferential mobility is explicitly considered in a simulated environment, wi th organisms confined in enclosures of a variety of sizes. Some simulations involve single populations, while others pit together competitors differin g only in mobility. Three foraging strategies based on simple movement prin ciples are simulated. Results indicate that the relationships between resou rce consumption and mobility will depend upon foraging strategy, often in u nexpected ways compared with the implications of spatial averaging. Outcome s of interactions among pairs of populations having the same foraging strat egy but with different mobilities also are complex, indicating that the res ults of confinement experiments may involve non-intuitive interactions betw een mobility and foraging method. There needs to be a refocusing on basic b iology of organisms used in confinement experiments (e.g. movement distribu tions) and, particularly, constructing defensible statements on why the sel ected scales were used. (C) 2000 Elsevier Science B.V. All rights reserved.