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Dietary studies are critical for understanding foraging strategies and have important applications in conservation and habitat management. We applied a robust metabarcoding protocol to characterize the diet of the critically endangered freshwater fish Zingel asper and conducted modelling and simulation analyses to characterize and identify some of the drivers of individual trophic trait variation in this species. We found that intra-specific competition and ontogeny had minor effects on the trophic niche of Z. asper. Instead, our results suggest that the majority of trophic niche variation was driven by seasonal variation in ecological opportunity (in our case, the seasonal variation in the availability of preferred prey types). Overall, our results are in line with the optimal foraging theory and suggest that Z. asper is specialized on a few ephemeropteran prey species (Baetis fuscatus and Ecdyonurus) but adapts its foraging by becoming more opportunistic as its favoured prey seasonally decline. Despite the now widespread usage of metabarcoding, very few studies have attempted to study inter- and intra-populational individual trophic traits variation with metabarcoding data. This study illustrates how metabarcoding data obtained from feces can be combined with modelling and simulation approaches to test hypotheses in the conventional analytic framework of trophic analysis.

International audience

International audience; Investigating processes and timing of differentiation of organisms is critical in the understanding of the evolutionary mechanisms involved in microevolution, speciation, and macroevolution that generated the extant biodiversity. From this perspective, the Telestes genus is of special interest: the Telestes species have a wide distribution range across Europe (from the Danubian district to Mediterranean districts) and have not been prone to translocation. Molecular data (mtDNA: 1,232 bp including the entire Cyt b gene; nuclear genome: 11 microsatellites) were gathered from 34 populations of the Telestes genus, almost encompassing the entire geographic range. Using several phylogenetic and molecular dating methods interpreted in conjunction with paleoclimatic and geomorphologic evidence, we investigated the processes and timing of differentiation of the Telestes lineages. The observed genetic structure and diversity were largely congruent between mtDNA and microsatellites. The Messinian Salinity Crisis (Late Miocene) seems to have played a major role in the speciation processes of the genus. Focusing on T. souffia, a species occurring in the Danube and Rhone drainages, we were able to point out several specific events from the Pleistocene to the Holocene that have likely driven the differentiation and the historical demography of this taxon. This study provides support for an evolutionary history of dispersal and vicariance with unprecedented resolution for any freshwater fish in this region. Citation: Dubut V, Fouquet A, Voisin A, Costedoat C, Chappaz R, et al. (2012) From Late Miocene to Holocene: Processes of Differentiation within the Telestes Genus (Actinopterygii: Cyprinidae). PLoS ONE 7(3): e34423.

CorrespondAnce: Emmanuel Corse, E-mail: emmanuel.corse@ univ-provence.fr; André Gilles, E-mail: andre.gilles@univ-provence. fr; International audience; The development of DNA barcoding from faeces represents a promising method for animal diet analysis. However, current studies mainly rely on prior knowledge of prey diversity for a specific predator rather than on a range of its potential prey species. Considering that the feeding behaviour of teleosts may evolve with their environment, it could prove difficult to establish an exhaustive listing of their prey. In this article, we extend the DNA barcoding approach to diet analysis to allow the inclusion of a wide taxonomic range of potential prey items. Thirty-four ecological clade-specific primer sets were designed to cover a large proportion of prey species found in European river ecosystems. Selected primers sets were tested on isolated animal, algal or plant tissues and thereafter on fish faeces using nested PCR to increase DNA detection sensitivity. The PCR products were sequenced and analysed to confirm the identity of the taxa and to validate the method. The methodology developed here was applied to a diet analysis of three freshwater cyprinid species that are assumed to have similar feeding behaviour [Chondrostoma toxostoma toxostoma (Vallot 1837), Chondrostoma nasus nasus (Linnaeus, 1758) and Barbus barbus, (Linneaus 1758)]. These three species were sampled in four different hydrographic basins. Principal Component Analysis based on prey proportions identified distinct perilithon grazer and benthophagous behaviours. Furthermore, our results were consistent with the available literature on feeding behaviour in these fish. The simplicity of the PCR-based method and its potential generalization to other freshwater organisms may open new perspectives in food web ecology

International audience; Étude de l'hybridation introgressive entre Chondrostoma t. toxostoma et Chondrostoma n. nasus (tÉlÉostÉen, Cyprinidae) en utilisant une approChe multiple par Caroline COSTEDOAT (1), Nicolas PECH (1), Rémi CHAPPAZ (1), Marie Dominique SALDUCCI (1), Puy LIM (2) & André GILLES (1) rÉsumÉ.-L'introduction d'espèces envahissantes et la destruction d'habitats naturels sont les principales causes de l'extinction des téléostéens durant le siècle dernier. L'introduction d'espèces peut représenter un danger pour la survie des espèces endémiques, tant au niveau écologique (compétition, prédation,…) que sur le plan génétique, notamment suite aux phénomènes d'hybridation et d'introgression qui ne font qu'exacerber la situation. C'est le cas de l'espèce endémique Chondrostoma t. toxostoma qui s'hybride avec l'espèce Chondrostoma n. nasus (introduite en 1860). Pour en étudier les conséquences génétiques, nous avons utilisé sept populations de C. t. toxostoma, six populations de C. n. nasus et deux zones hybrides, représentant 568 spécimens. Nous avons utilisé quatre caractères méristiques, 18 loci enzymatiques et 500 pb du gène mitochondrial cytochrome b. Nous démontrons l'absence de barrière reproductive entre les deux espèces de chondrostomes, la capacité introgressive de leur génome tant au niveau mitochondrial que nucléaire et la survie des individus hybrides. La combinaison de ces trois différents marqueurs constitue un outil puissant dans la détection des différents niveaux d'hybridation. Cette étude est la première à tenir compte de l'hybridation afin de protéger et de conserver l'espèce endémique Chondrostoma t. toxostoma. abstraCt.-Study of introgressive hybridization between Chondrostoma t. toxostoma and Chondrostoma n. nasus (Teleostei, Cyprinidae) using multiple approaches.