L. Forró szerk.: Miscellanea Zoologica Hungarica 9. 1994 (Budapest, 1994)

Csányi, B.: The macrozoobenthon community of the Danube between Rajka and Budapest

Classification and ordination of the kick and dredge samples The hierarchical classification (cluster analysis) of both data-groups, resulted in highly similar dendrograms. Different similarity functions were used. The upper Hungarian river stretch (sampling sites 1-4 in the Szigetköz) formed one subgroup (Figs 3 and 4), connected to the other sites in a chain-like structure. The so called "chain effect" (i.e. the addition of the new sampling sites to the previous group, without forming any new sub-group) suggests a continuous change in the macrozoobenthic fauna along the Danube, where new species occur in the community (increasing taxon number). The sampling sites and the corresponding taxa are illustrated on rotating plots. The common taxa occuring at many sampling sites are responsible for the central position of those sites (Fig. Jaccard Chord distance Euclidean distance 0.2 O.l O . 2 O.l 4 3 2 1 Fig. 3. Dendrograms of sampling sites of the Danube based on macrozoobenthon taxa collected by kick sampling