ECOLOGY OF TESTACEANS (PROTOZOA, RHIZOPODA) IN MIRES IN SOUTHERN FINLAND .2. MULTIVARIATE-ANALYSIS

The distribution of 41 testacean species (Protozoa: Rhizopoda) and a rotifer, Habrotrocha angusticollis (Rotifera: Bdelloidea) was analyzed in relation to 12 environmental variables by multivariate numerical techniques. Statistical analyses were performed using absolute numbers of testaceans estimated from 90 representative microsite types in six mires in the raised bog region of southern Finland. Two-way indicator species analysis (TWINSPAN) and both indirect (DCA) and direct (CCA) gradient analysis indicated that individual testaceans and certain assemblages of testaceans were dependent upon more than a single environmental factor, with soil moisture content being the most important. In microsite types where soil moisture content was not strongly affecting testaceans, the trophic status and DOC of the water proved to be important. The 12 environmental variables included in our survey accounted for 69.1 % of the total variance according to the CCA-ordination. In decreasing order of importance were depth of water table, soil moisture content, trophic status of the site, C/N ratio of the peat, water pH, depth of testacean sample, and DOC of water. The agglomerative cluster analysis by means of VAN DER MAAREL'S similarity index recognized nine testacean groups, which are comparable to groups identified by TWINSPAN along ecological gradients from dry to wet and from oligotrophic to eutrophic microsites.