Relationships among testate amoebae (Protozoa), vegetation and water chemistry in five Sphagnum-dominated peatlands in Europe

To study the relationships between groups of organisms and the degree to wh ich these relationships are consistent across major climatic gradients, we analysed the testate amoeba (Protozoa) communities, vegetation and water ch emistry of one peatland in five countries: Switzerland, The Netherlands, Gr eat Britain, Sweden and Finland, as part of the BERI (Bog Ecosystem Researc h Initiative) project. The relationships between the different data sets an d subsets were investigated by means of detrended correspondence analysis, canonical correspondence analysis and Mantel permutation tests. The compari son of data on vegetation and testate amoebae showed that inter-site differ ences are more pronounced for the vegetation than for the testate amoebae s pecies assemblage. Testate amoebae are a useful tool in multi-site studies and in environmental monitoring of peatlands because: (1) the number of spe cies in Sphagnum-dominated peatlands is much higher than for mosses or vasc ular plants; (2) most peatland species are cosmopolitan in their distributi ons and therefore less affected than plants by biogeographical distribution patterns, thus differences in testate amoeba assemblages can be interprete d primarily in terms of ecology; (3) they are closely related to the ecolog ical 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 func tioning of peatland ecosystems. This study revealed the existence of small- scale vertical gradients within the vegetation and life-form niche separati on 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 n ear the ground water table, whereas the mosses are not. Testate amoebae wer eshown to be ecologically more closely related to the chemistry of water sa mpled at or near the water table level and to the mosses than to the deep-r ooted plants.