Can tentacle pigmentation help distinguish between non-native and native populations of <i>Gyraulus parvus</i> in Europe?

ABSTRACT The freshwater snail Gyraulus parvus is represented in Europe by two mitochondrial lineages, one of which corresponds to the native European population and the other to the invasive lineage of North American origin. These two lineages were traditionally considered as separate species based on morphological characters, one representing G. parvus and the other Gyraulus laevis. However, a recent molecular analysis has revealed the plasticity of morphological traits along with the conspecific nature of these two taxa, with the former having taxonomic priority. As the North American lineage is highly invasive in Europe and appears to be genetically displacing the rare European native lineage, easy identification of its origin in the field would significantly improve conservation decisions and, ultimately, help maintain intraspecific variation of this species. In this study, we investigated the potential of tentacle pigmentation as a reliable morphological character to distinguish between these two lineages. Genetic analyses consistently revealed two major haplogroups based on mitochondrial and nuclear markers. These haplogroups were significantly congruent with the pigmentation of the tentacles, with individuals of North American or European origin having pigmented or unpigmented tentacles, respectively. However, two types of deviations from this pattern were observed, suggesting possible mitochondrial introgression or intraspecific variation in this character. These results support previous conclusions about the conspecificity of the European and North American lineages. Despite the observed variation, tentacle pigmentation has proven useful in identifying the origin of G. parvus populations, especially because all individuals with unpigmented tentacles found so far in Europe belong to the rare native lineage.