Because of interspecific hybridization, there is considerable controversy over the taxonomic status of many members within the family Cyprinidae. In this study, morphological and genetic characters of Leuciscus soufia, a cyprinid fish of southern France and northern Italy, were examined to verify the existence of three subspecies. Leuciscus soufia agassizi differs from Leuciscus soufia multicellus in morphology, in heterozygosity at two diagnostic allozyme loci, and by distinct mitochondrial lineages. Leuciscus s. soufia is morphologically similar to L. s. agassizi but exhibits decreased enzymatic polymorphism. However, two specimens of L. s. soufia from the Var River were found to have mitochondria of the subspecies multicellus, while four Bevera River specimens of L. s. multicellus possessed the mitochondria of the subspecies agassizi. These data argue in favour of introgressive hybridization between L. s. soufia and L. s. multicellus, rejecting the hypothesis that an ancestral population was fragmented, generating three "subspecies" that retained the original polymorphism. We propose that L. s. soufia and L. s. agassizi be regrouped within the soufia subspecies. A calibrated molecular clock dates the separation of the remaining subspecies back to the Messinian (5 million years ago). Sea level fluctuations likely mediated their secondary contact and subsequent introgressive hybridization.Résumé : À cause de l'hybridation interspécifique, le statut taxonomique de nombreux membres de la famille des Cyprinidés est au coeur d'un important débat. Dans le cadre de la présente étude, les auteurs ont examiné les caractères morphologiques et génétiques de Leuciscus soufia, cyprinidé vivant dans le sud de la France et le nord de l'Italie, afin de vérifier l'existence de trois sous-espèces. L. s. agassizi diffère de L. s. multicellus sur le plan morphologique, par l'hétérozygotie observée à deux loci de diagnostic des allozymes et par des lignées distinctes de mitochondries. L. s. soufia est morphologiquement similaire à L. s. agassizi, mais présente un polymorphisme enzymatique moindre. Toutefois, chez deux spécimens de L. s. soufia du Var, on a trouvé des mitochondries appartenant à la sous-espèce multicellus, tandis que quatre spécimens de L. s. multicellus de la Bevera possédaient des mitochondries de la sous-espèce agassizi. D'après ces données, il y aurait eu une hybridation introgressive entre L. s. soufia et L. s. multicellus, et nous pouvons rejeter l'hypothèse selon laquelle une population ancestrale aurait été fragmentée, ce qui aurait produit trois « sous-espèces » retenant le polymorphisme original. Nous proposons de regrouper L. s. soufia et L. s. agassizi dans la sous-espèce soufia. Une horloge moléculaire étalonnée fait remonter la séparation de l'autre sous-espèce à l'époque messinienne (5 millions d'années). Les variations du niveau de la mer ont probablement été les médiateurs du contact secondaire des sous-espèces et de leur hybridation introgressive subséquente.[Traduit par la Rédaction] Gilles et al....

Annual monitoring of the apron Zingel asper in the Durance River, a tributary of the Rhône in which the fish is endemic, indicated its narrow diet range. Three types of prey made up the basic diet: Diptera (Simulidae and Chironomidae), mainly in winter, and Ephemeroptera (Baetidae) and Trichoptera (Hydropsychidae), during the rest of the year. Although some potential prey (Coleoptera and Gammaridae) were present in the substratum, they were not found in the stomach contents of the apron. In spring specific food items (Heptageneidae) appeared to be actively searched for as indicated by stomach contents. This period coincided with the renewal of growth. More than 80% of the annual occurred before the beginning of autumn.

High mountain lakes are a network of sentinels, sensitive to any events occurring within their waterbodies, their surrounding catchments and their airsheds. By modifying nutrient balance and availability in water, both local and global changes are expected to alter primary productivity and to trigger strong ecological impacts in these ecosystems. Predicting ecological trajectories under future change is a key challenge for both scientists and conservation managers. French alpine lakes, in the most southern and western part of the European Alps, have received surprisingly little attention to date. In this article, we address how variations in nitrogen (N) and phosphorus (P) supply are likely to impact the area's phytoplankton growth. We performed N and/or P enrichment microcosm experiments under controlled conditions on 12 phytoplankton assemblages sampled during the summer 2016 in four French alpine lakes with contrasting catchments and N‐deposition regimes. The nutrients limiting phytoplankton growth varied according to the nutrient stoichiometry of the lake water. In the lakes exposed to high N‐deposition rates (≈700 kg N km–2 year–1), the water contained more N than P and phytoplankton growth in microcosms was either limited by P or not limited by either N or P. In the lakes exposed to low N‐deposition rates (≈500 kg N km–2 year–1), N availability relative to P was lower in the lake with vegetated catchment than in the lake with rocky catchment, resulting in a switch from P to NP colimitation of the phytoplankton in microcosms. Our data clearly indicate that French alpine lakes do not host the same diversity and structure of phytoplankton communities and that phytoplankton composition influenced phytoplankton growth in microcosms. First, we show that nonmotile colonial chlorophytes appeared in late summer assemblages, with lower growth rates but P‐storage abilities. Second, our findings indicate that the growth of phytoplankton assemblages dominated by diatoms was increasingly limited by silica (SiO2) throughout the summer, along with a 70% decrease in SiO2 concentration in lake water. The forecast global changes in the French Alps should increase phytoplankton growth in most high mountain lakes where P is the main limiting nutrient, before NP colimitation. These changes are likely to be of lesser extent in lakes with large vegetated catchments in the northern area with lower N‐deposition rates and of greater extent in the southern area with higher N‐deposition rates and future P‐deposition rates. By investigating the relationship between nutrient availability, phytoplankton composition and phytoplankton growth rate, this experimental laboratory microcosm study will help interpret current multifactorial data from in situ monitoring networks in the Alps. It will also be helpful to develop models to better predict the sentinel lake responses to local and global changes.

Plan Vianney lake, situated in the Oisans massif (French Alps) at an altitude of 2250 m, has a fish fauna composed of brook trout, Salvelinus fontinalis (Mitchell), and Artic charr, Salvelinus alpinus (L.). The present study examines the feeding behaviour of S. fontinalis in 1993–94 but also gives some data on S. alpinus. The brook trout represented 80% of the fish fauna of the lake. Dietary analysis showed that this species is an opportunistic feeder and revealed similarities in the trophic niches of S. fontinalis and S. alpinus and a low level of potentially available food resources. The annual growth of S. fontinalis was short and the growth rate was slow compared with other populations. Under these extreme conditions, female fish required several summers to replenish their reserves of energy and were only in condition to spawn once every 2 or 3 years. Although the fecundity of the population was low, it was sufficient to maintain the species in the lake which is not exploited.

High mountain lakes are a network of sentinels, sensitive to any events occurring within their waterbodies, their surrounding catchment and their airshed. In this paper, we investigate how catchments impact the taxonomic and functional composition of phytoplankton communities in high mountain lakes, and how this impact varies according to the atmospheric nutrient deposition regime. For two years, we sampled the post snow-melt and the late summer phytoplankton, with a set of biotic and abiotic parameters, in six French alpine lakes with differing catchments (size and vegetation cover) and contrasting nitrogen (N) and phosphorus (P) deposition regimes. Whatever the nutrient deposition regime, we found that the lakes with the smallest rocky catchments showed the lowest functional richness of phytoplankton communities. The lakes with larger vegetated catchments were characterized by the coexistence of phytoplankton taxa with more diverse strategies in the acquisition and utilization of nutrient resources. The nutrient deposition regime appeared to interact with catchment characteristics in determining which functional groups ultimately developed in lakes. Photoautotroph taxa dominated the phytoplankton assemblages under high NP deposition regime while mixotroph taxa were even more favored in lakes with large vegetated catchments under low NP deposition regime. Phytoplankton functional changes were likely related to the leaching of terrestrial organic matter from catchments evidenced by analyses of carbon (δ 13 C) and nitrogen (δ 15 N) stable isotope ratios in seston and zooplankton. Plankton δ 15 N values indicated greater water-soil interaction in lakes with larger vegetated catchments, while δ 13 C values indicated the effective mineralization of the organic matter in lakes. There is even more reason to consider the role played by catchments when seeking to determine the vulnerability of high altitude lakes to future changes, as catchments' own properties will vary under changes related to climate and airborne contaminants.