Comparing Species Diversity and Evenness Indices

Extract

The current interest in diversity as one of the major parameters describing a community has led to an increasing number of published results and theoretical discussions during the last years. Diversity has variously been related to other attributes of the community or properties of the environment, among which time, spatial heterogeneity, stability, primary production, productivity, competition, predation, niche structure and evolution. Although this rather overwhelming amount of possible relations seems somehow too much of a good thing, the importance of diversity remains well established in current ecological theory. One of the most important applications of diversity indices is their usage in the biological assessment of pollution. This immediately raises the problem of comparing diversity indices within habitats in time or between habitats in communi-ties. These comparisons are frequently made, yet the statistical significance of the observed differences or similarities is seldom mentioned. A test for these differences was formulated by Hutcheson (1970) but it apparently failed to attract the attention it deserves. In this study it was our purpose to investigate the distributions of the more important diversity indices and their evenness components in a low-diversity community of meiobenthic copepods of a shallow brackish water pond in northern Belgium. In this habitat the number of species is rather low, which greatly simplifies the analysis, and we hope that the statistical behaviour of the indices we find will hold for other, especially other low diversity communities as in polluted environments, as well. We chose copepods because they are taxonomically well known, the benthos because it is approximately two-dimensional and a shallow environment because of the possibility of accurate sampling.