Thecamoebians from the small streams of the Boubín area (?umava Mts,Czech Republic)

From 1999–2005, seventy-eight samples were collected from the small streams in the area of the Boubín Mountain including also the natural preserve “Boubínsky prales” (Boubín primeval forest) (Šumava Mts, Czech Republic). Nineteen species of thecamoebians were identified in the samples; the most abundant species were Centropyxis orbicularis, Pontigulasia compressa, Centropyxis aculeata, Difflugia oblonga and Centropyxis arcula. Species composition of assemblages as well as ecological affinities of the most common taxa are comparable with data from the previously analysed streams in the Šumava Mts. This correlation improves the quality of data for environmental preferences of thecamoebian assemblages contained in the streams and these can be used for interpretation of ancient environments. Though species composition of assemblages changes gradually, two end-member assemblages can be defined. For both assemblages, environmental conditions were defined: Lower-diversity assemblages dominated by centropyxids originated mainly from standing water with low content of organic debris. Relative abundances of C. orbicularis showed negative correlations with abundances of other Centropyxis spp. which may indicate different ecological affinities of this species. Centropyxis orbicularis may tolerate higher levels of fine organic debris in stream sediments. Assemblages with common to abundant occurrences of P. compressa and/or D. oblonga prefer running water. Difflugia oblonga dominated in samples with higher content of fine organic debris. Relation between test size of D. oblonga and flow rate was recorded: large D. oblonga prevailed in standing water while small specimens dominated in fast streams.