To study the relationships between groups of organisms and the degree to which these relationships are consistent
across major climatic gradients, we analysed the testate amoeba (Protozoa) communities, vegetation and water
chemistry of one peatland in five countries: Switzerland, The Netherlands, Great Britain, Sweden and Finland,
as part of the BERI (Bog Ecosystem Research Initiative) project. The relationships between the different data sets
and subsets were investigated by means of detrended correspondence analysis, canonical correspondence analysis
and Mantel permutation tests. The comparison of data on vegetation and testate amoebae showed that inter-site
differences are more pronounced for the vegetation than for the testate amoebae species assemblage. Testate
amoebae are a useful tool in multi-site studies and in environmental monitoring of peatlands because: (1) the
number of species in Sphagnum-dominated peatlands is much higher than for mosses or vascular plants; (2) most
peatland species are cosmopolitan in their distributions and therefore less affected than plants by biogeographical
distribution patterns, thus differences in testate amoeba assemblages can be interpreted primarily in terms of
ecology; (3) they are closely related to the ecological characteristics of the exact spot where they live, therefore they
can be used to analyse small-scale gradients that play a major role in the functioning of peatland ecosystems. This
study revealed the existence of small-scale vertical gradients within the vegetation and life-form niche separation
in response to water chemistry. The deep-rooted plants such as Carex spp. and Eriophorum spp. are related to the
chemistry of water sampled at or near the ground water table, whereas the mosses are not. Testate amoebae were
shown to be ecologically more closely related to the chemistry of water sampled at or near the water table level
and to the mosses than to the deep-rooted plants.