A method to detect higher order interactions in ecological communities

Higher order interactions are present in ecological communities when the effect of one species on the per capita growth rate of another depends not only on the first species. A method to detect such interactions in ecological communities is devised. As in a previous approach by Case and Bender (1981), the method checks if the per capita growth rate of a species can be expressed as a sum of terms each one of which depends only on one species. If that expression is not possible there are higher order interactions. However Case and Bender (1981), as well as other authors in subsequent studies, calculate the per capita growth rates with methods which can introduce errors. These methods also make assumptions about the mechanisms involved in the regulation processes which are not very realistic. The method proposed here alleviates these problems. It has the limitation, however, of needing short time intervals. The method is applied to experimental data of insect communities, and the results indicate that, in various analysis of 2-species communities, there are no reasons to suspect the existence of higher order interactions. (C) 1999 Elsevier Science B.V, All rights reserved.