1. The effects of natural and human-induced variability on the composition of macroinvertebrate communities of 28 ponds located in the North Iberian Plateau (Spain) were studied to determine the best predictors of community structure.
2. Constrained ordination was used to identify the main factors explaining the among-pond variance in abundance (as catch per unit effort) of total macroinvertebrate and Chironomidae assemblages and trophic structure (functional feeding groups).
3. Variance partitioning showed that human disturbance (represented by a pond condition index, total phosphorus concentration and pesticides) was the best predictor of macroinvertebrate community structure, whereas factors, such as habitat and biotic variables were of secondary importance. Factors controlling the chironomid community were broadly similar to those acting on the whole community of macroinvertebrates. In contrast, trophic structure was mainly determined by habitat and biotic variables.
4. Our results show that macroinvertebrates may be used as effective indicators of the ecological status of Mediterranean ponds. The Chironomidae deserve special attention because they were the dominant group in the study ponds and the strongest explanatory variable for their distribution was degradation.