A weighted coenotic index (WCI): Description and application to soil animal assemblages

The Weighted Coenotic Index (WCI) is a single value that unifies total abundance, dominance structure, species richness and ecological weightings, e.g., habitat preferences and positions of species in the r/K continuum. Studies with simulated species assemblages have shown that ecological weightings and dominance structure are major components of the index; the ecological weightings must be related to the group of organisms studied and to the scope of the investigation. The WCI is a relative measure that needs a reference (control) site in each investigation for a conclusive interpretation. Compared to several diversity indexes, the WCI has a much better discriminant ability because it includes ecological weightings and a log-normal dominance structure. This index has been applied to published data from several field studies using protozoa (testate amoebae, ciliates) and earthworms. The results show that the WCI is an appropriate tool to measure changes and to monitor recovery processes in disturbed ecosystems. The index should be calculated separately for each systematic (indicator) group (e.g., ciliates, nematodes, mites) because the information will be more detailed and an overall index could, for instance, mask a high value for one group, such as ciliates, in conjunction with a low value for another group, such as nematodes. The WCI has been developed on a protozoological background owing to the authors' familiarity with this field. Mathematically and practically it is also applicable to other groups of soil and freshwater organisms.