Diversity and distribution patterns of benthic invertebrates along alpine gradients. A study of remote European freshwater lakes

Invertebrates inhabiting alpine water bodies are sensitive to environmental variability and lake faunal communities can therefore be important indicators of long-range airborne pollution, climate change and other human impacts. Information about the trophic structure and species composition of alpine lake ecosystems over space and time should therefore give important insights into environmental change effects. To explore the sensitivity of the faunal communities to environmental variability at local and regional scales we sampled biological and environmental variables from alpine lakes in seven different alpine lake districts in six European mountain regions. The fauna of the lakes was mainly composed of oligotrophic/ultraoligotrophic species, predominantly chironomids which made up more than 60% of all individuals. Species accumulation curves were used to explore patterns of species turnover and distribution, and the results indicated strong patterns in species diversity and also environmentally driven patterns in species distributions among lake districts. We used ordination analyses to explore these patterns in more detail. The results showed that the over-riding patterns in faunal assemblages were found between the lake districts. Lake-water chemistry appeared to be the major driver of the faunal assemblages at this scale, but altitude and geography could also account for significant fractions of the variability. In addition to these broad-scale patterns, repeatable trends in the faunal assemblages could be found in the faunal assemblages within lake districts. At this scale, the strongest compositional trends were found along the altitudinal gradient, but the faunal communities also responded to within-district variability in lake-water chemistry. Lake size or maximum depth did not appear to have any statistically significant effect on the littoral faunal assemblages at either scale.Gli invertebrati che colonizzano gli ambienti acquatici d\u27alta quota sono sensibili alle variazioni ambientali e le loro comunit? possono essere utili indicatori di trasporto di inquinanti, cambiamenti climatici e altri impatti antropici. Informazioni relative alla struttura trofica e alla composizione in specie degli ambienti lacustri possono fornire utili informazioni sugli effetti dei cambiamenti climatici. Per definire la sensibilit? delle comunit? lacustri alle variabilit? ambientali su scala regionale e locale abbiamo campionato laghi in 7 diversi distretti alpini appartenenti a 6 regioni montane europee. Le curve di accumulo utilizzate hanno fornito informazioni relative al turn-over di specie ed alla loro distribuzione. L\u27idrochimica lacustre sembra essere uno dei principali fattori determinanti la struttura di comunit? fra i diversi distretti, l\u27altitudine e la distribuzione geografica hanno anche un ruolo importante