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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. [ABSTRACT FROM AUTHOR]

Although a large number of rivers stretches in Southeast Europe (SEE) have a pristine status compared to the rest of Europe, these ecosystems and their freshwater biodiversity are perceptibly threatened. Since crayfish species are known to cover a wide spectrum of ecological functions they are considered as keystone species and ecosystem engineers. Therefore, their decline may substantially impair local biodiversity and ecosystem services. In this manuscript we present a brief overview of the status of the native freshwater crayfish and their habitats in SEE. Different forms of physical habitat degradation as well as invasive alien crayfish species and their pathogens (e.g., Aphanomyces astaci) are simultaneously threatening endangered populations all over SEE. Even though all native crayfish species are listed in the IUCN Red List, so far none of the 33 LIFE rehabilitation projects performed in SEE, has crayfish as target species in their agenda. Furthermore, SEE countries rarely designated Natura 2000 sites for native crayfish. We propose future studies to assess the distribution and functional role of crayfish species in SEE, as well as to develop habitat suitability models for these species during future conservation projects.

The protected European stone crayfish, Austropotamobius torrentium, is a host to epibionts inhabiting its exoskeleton. Despite evidence of the close association of these epibionts to the crayfish and the beneficial services provided for the crayfish, the main factors influencing their occurrence, distribution and abundance are still poorly understood. In order to investigate the stone crayfish epibiont community, the ecological requirements of individual species, and aspects of the host-epibiont relationship we collected data at several crayfish populations in Austria, Switzerland and Germany. At each location, we recorded the epibiont position on the crayfish host along with a number of biotic and abiotic parameters. Apart from recording the Branchiobdella species B. parasita, B. hexadonta, B. pentadonta and B. balcanica, we detected for the first time the polychaete Hystricosoma chappuisi in the European Alps. Species-specific biogeographical and habitat factors such as river catchment borders, crayfish length, water temperature and nutrients concentration were identified to be important for the occurrence and abundance of epibionts. Branchiobdella species were strongly linked to certain host body areas, providing evidence for the existence of different functional traits within the annelid assemblage. With this study we demonstrate that the crayfish–epibionts relationship includes structural and functional complexities that can be important for defining management units in future conservation policies. Due to benefits for the mutualistic relationship, restocking and reintroduction actions are likely to be more successful, if ecological requirements of both the host and the epibiont species are considered.

The accelerating climate crisis intensifies environmental changes in high‐altitude ecosystems worldwide, with rising air temperature among the main stressors. While past research in alpine streams has primarily focused on how retreating glaciers might affect the ecology of glacier‐fed streams on the long run, observations of real‐time alterations of water temperature in such pristine environments are rare. Using long‐term measurements of water temperature (2010–2017) together with datasets on benthic invertebrate communities from 18 glacial and nonglacial alpine and subalpine streams in the European Alps, we illustrate significant ecological relationships of water temperature regimes and the identity of benthic communities and forecast changes thereof due to considerable warming of stream water. Besides reporting multiannual warming of all observed streams during summer with a mean rate of 2.5(±0.6)°C decade−1, this work redefines temperature optima and ranges using robust regression modelling and thereby identifies potential winners and losers among the invertebrate species. We conclude that the various invertebrate taxa in alpine stream networks will respond differently to thermal alterations and that the herein modelled temperature ranges of invertebrates is an essential step towards the understanding of future shifts in species distributions and success. [ABSTRACT FROM AUTHOR]