Deciphering the evolutionary biology of freshwater fish using multiple approaches – insights for the biological conservation of the Vairone (Leuciscus souffia souffia)

International audienceThe organisation of genetic variability is of primary importance in designing conservation strategies. In this context, the conservation units are often defined using the concept of Evolutionary Significant Units (ESUs) what could appear as a useful guide but are very rarely used. Another difficulty arises when species hybridise as it is the case in cyprinid fishes for which the debate joins discussions on the species definitions. For example, the vairone, Leuciscus souffia (Teleostei: Cyprinidae) is a protected species (IUCN, Bern convention, Habitat directive) but current legislation does not take into account its ambiguous taxonomic status, neither its genetic variability nor its ecological preferences. In this paper, we examine the genetic structure and phylogeography of the subspecies Leuciscus souffia souffia in its range (France) with a combination of morphology, allozymes and mitochondrial DNA sequences using analyses mainly based on AMOVA and nested clade analysis. We then decipher the evolutionary biology of this fish as the combined analysis of morphology, nuclear and mitochondrial markers displays decoupling between morphological homogeneity and moderate genetic differentiation, suggesting that Management Units (following Moritz' definition) should be designed. We conclude by proposing directions both for the protection of endangered populations and for the conservation of evolutionary potential based on the evolutionary dynamics found for the examined populations in the light of the most-often used definitions of ESUs