Tomáš Soldán

Prediction of Changes in Ephemeropteran Communities — A Transition Matrix Approach

Quantitative monthly samples, taken from 150 evenly distributed localities in the Labe basin, Czechoslovakia, during two research periods in the 1950’s and 1970’s were classified using a saprobiologi-cal classification (Czechoslovak National Standards Nos 830532 and 830602) and the TWINSPAN method (numerical hierarchical polythetic classifications). Transition matrices, i.e. matrices of transition probabilities between particular types, were constructed for each of the methods of mayfly community classification used. All the “matrices” reflect the tendency of the water quality to gradually deteriorate as indicated by changes in mayfly communities. The classification by saprobity classes seems to be too coarse for predictive purposes (most localities fall into betamesosaprobity class). Combined information from matrices based on saprobial index classes and TWINSPAN provided reasonable description of the process.