Abstract
Four mayfly taxocoena which correspond to zones in the river continuum concept of Vannote et al. (1980) and to the zonation concept of Illies & Botoşaneanu (1963), were distinguished by cluster analysis in the Belá River basin, Slovakia.
By principal components analysis, taxocoena were shown to be separated along a complex gradient dominated by altitude and slope.
An increase of species diversity was observed downstreams. The species-diversity data can be fitted to a geometric series, and interpreted by the niche preemption hypothesis. Equitability and the ratio of Baetidae to Heptagenidae are supposed to indicate ecological conditions.
