Abstract
Earthworms represent an important part of soil macrofauna. Their activity has direct and indirect impacts on the water, nutrients and carbon cycles; it conditions the structure and fertility of soils. That is why earthworms are considered the engineers of the soil ecosystem. Earthworms feed on organic matter on the surface and in the soil; this organic matter tends to form chemical complexes with the soil metals. That is why worms were adopted by the international community for ecosystem diagnosis, and particularly for the study of the potential environmental impact of metal contaminants in the soil. In this context, this project focuses on three earthworm species of the Lumbricus kind. We propose first to determine, in these three species, if the colonisation of polluted sites has had consequences on the distribution of neutral genetic diversity in the population. A species’ genetic diversity indeed determines its response capacity to natural or anthropogenic changes. An erosion of this diversity can be observed after a chemical contamination of the habitat, either because of the selection of genotypes which tolerate it, or of demographic events. In order to evaluate the demographic consequences of metallic pollution, we will compare the diversity and neutral genetic differentiation in populations from polluted and non polluted sites. In addition, we propose to determine if a long term exposure to trace metals of anthropogenic origin can constitute sufficient selection pressure to affect the genetic diversity structure of selected genes (like metal detoxification). This will allow us to test if certain target genes could have been involved in the evolution of an adaptation to metals in populations that have been living on polluted soils for several generations.
France