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RESEARCH PRODUCT

Cd-resistance in field Gammarus populations: genetic adaptation, transgenerational effect, or selection of phylogenetic cryptic lineages?

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International audience; We have recently identified a field population of the crustacean Gammarus fossarum historically-exposed (geochemical background) to cadmium (Cd) that exhibits a resistance transmissible to offspring. This population constitutes a good case study to investigate mechanisms underlying population’s resistance to long-term exposure to contamination that are of deep concern for ERA, especially in the field. In order to gain insights into the determinism of the Cd-resistance observed in this historically-exposed population, we applied quantitative genetic protocols both in two Cd-naive populations and in the resistant one. In addition, because G. fossarum is known to constitute a complex of cryptic species with potentially heterogeneous sensitivities to contaminants, we also tested whether this resistance could be explained by the selection of a peculiar phylogenetic group among the Gammarus diversity (based on COI genotyping). Our work reveals that the Cd-resistant population does not belong to a specific lineage and sustains that its resistance to Cd is due to transgenerational maternal effect induced by exposure in the field. Whether this transmissible resistance is fixed (phenotypic plasticity) or transitory (flexibility) is still to be investigated to decipher the role of acclimation in population resistance. Also, parental effects seem to be a key endpoint to understand the modification of sensitivities to contaminants in the field, and taking into account this phenomenon is mandatory to improve the relevance of ERA.