Chironomids of the genus Diamesa (Meigen, 1835, Diptera: Chironomidae) inhabit cold, oxygen-rich running waters. We have investigated the presence of Diamesa and other freshwater macroinvertebrates at 22 stream sampling sites in 3 European high mountain regions (the Central Pyrenees, the Ötztal Alps, and the Tatra Mountains) to establish suitable temperature conditions for Diamesa dominance. It has been generally accepted that their high abundance was linked to the presence of glaciers; however, we have shown that in the Tatra Mountains, where there are no glaciers, the conditions for the dominance of Diamesa species are created due to permanent snowfields, the geographical orientation of the valley and shading by the surrounding high peaks. The historical connection of Diamesa to glaciers was investigated from the paleolimnological records of subfossil chironomid assemblages from the Bohemian Forest, where glaciers disappeared before or during the Late Glacial period. As expected, water temperature seems to be the main driver of Diamesa distribution, and we determined that the relative abundance of Diamesa species was significantly higher at the sites with a mean July water temperature below 6.5 °C. The Diamesa-dominated stream communities seems to be endangered due to ongoing climate warming and this assumption is supported by our paleolimnological results from the Bohemian Forest lakes, where Diamesa has disappeared due to warming of lake inflows at the beginning of the Holocene. These findings strengthen the former suggestions that some Diamesa species could be used as an indicator for tracking recent environmental changes in vulnerable ecosystems of cold mountain streams.

Continental Ecology Department Centro de Estudios Avanzados de Blanes CSIC Accés a la Cala St Francesc 14 17300 Blanes Spain

Department of Biology and General Ecology Faculty of Ecology and Environmental Sciences Technical University in Zvolen T G Masaryka 24 SK 960 01 Zvolen Slovakia

Department of Forest Ecology Faculty of Forestry and Wood Sciences Czech University of Life Sciences Prague Kamýcka 129 Prague CZ 165 21 Czech Republic

Department of Hydrochemistry and Ecosystem Modelling Institute of Hydrobiology Biology Centre Czech Academy of Sciences Na Sádkách 702 7 CZ 370 05 České Budějovice Czech Republic

Faculty of Natural Sciences Matej Bel University Tajovského 40 SK 974 01 Banská Bystrica Slovakia

Institute for Environmental Studies Faculty of Science Charles University Benátská 2 CZ 128 00 Praha 2 Czech Republic

Institute for Zoology University of Innsbruck Technikerstrasse 25 A 6020 Innsbruck Austria

Institute of Zoology Slovak Academy of Sciences Dúbravská cesta 9 SK 845 06 Bratislava Slovakia

Laboratory of Molecular Ecology and Mycology Institute of Botany Plant Science and Biodiversity Center Slovak Academy of Sciences Dúbravská cesta 9 Bratislava SK 845 23 Slovakia

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