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International audience; The impact of glacier retreat on fungal-driven decomposition in rivers is investigated using a standardized test across six countries. Less glacier cover is linked to increased decomposition, which is in turn associated with a greater abundance of fungi and a fungal cellulose-degrading gene, cbhI.Climate change is altering the structure and functioning of river ecosystems worldwide. In mountain rivers, glacier retreat has been shown to result in systematic changes in aquatic invertebrate biodiversity, but the effects of ice loss on other biological taxa and on whole-ecosystem functions are less well understood. Using data from mountain rivers spanning six countries on four continents, we show that decreasing glacier cover leads to consistent fungal-driven increases in the decomposition rate of cellulose, the world's most abundant organic polymer. Cellulose decomposition rates were associated with greater abundance of aquatic fungi and the fungal cellulose-degrading Cellobiohydrolase I (cbhI) gene, illustrating the potential for predicting ecosystem-level functions from gene-level data. Clear associations between fungal genes, populations and communities and ecosystem functioning in mountain rivers indicate that ongoing global decreases in glacier cover can be expected to change vital ecosystem functions, including carbon cycle processes.

International audience; AbstractSpecies taxonomy of bumblebees (Bombus Latreille, 1802) is well known to be problematic due to a potentially high intra-specific variability of morphological traits while different species can converge locally to the same color pattern (cryptic species). Assessing species delimitation remains challenging because it requires to arbitrarily select variable traits whose accuracy continues to be debated. Integrative taxonomic approach seems to be very useful for this group as different independent traits are assessed to propose a rational taxonomic hypothesis. Among operational criteria to assess specific status, the reproductive traits involved in the pre-mating recognition (i.e., the male cephalic labial gland secretions, CLGS) have been premium information. Since these secretions are supposed to be species-specific, these chemical traits can bring essential information where species delimitation is debated. Here, we describe and compare the CLGS of 161 male specimens of nine Alpinobombus taxa: alpinus, balteatus, helleri, hyperboreus, kirbiellus, natvigi, neoboreus, polaris, and pyrrhopygus. We aim also to test the congruence between this new information (reproductive traits) and published genetic dataset. Our results emphasized six distinct groups with diagnostic major compounds: (a) alpinus + helleri with hexadec-9-en-1-ol; (b) polaris + pyrrhopygus with two major compounds hexadec-9-en-1-ol and hexadec-9-enal; (c) balteatus with tetradecyl acetate; (d) kirbiellus with geranyl geranyl acetate; (e) hyperboreus + natvigi with octadec-11-en-1-ol; (f) neoboreus with octadec-9-en-1-ol. Based on this new information, we can confirm the species status of B. alpinus, B. balteatus, B. hyperboreus, B. kirbiellus, B. neoboreus, and B. polaris. We also confirm the synonymy of helleri (Alps) with alpinus (Sweden). However, the specific status of natvigi (Alaska) and pyrrhopygus (Sweden) is questionable and these taxa do not have specific CLGS composition.