Impact of quarrying on genetic diversity: an approach across landscapes and over time

Land conversion is one of the major global changes that threaten population viability. As with many industrial activities, quarrying highly modifies land cover, destroying previous habitats but also creating new conditions potentially supporting functioning and connectivity of pioneer species. Using a multi-landscape and -temporal approach, we assessed the impact of quarrying on the genetic diversity of two amphibians with contrasted ecological constraints: the common toad ( Bufo bufo ) and the natterjack toad ( Bufo calamita ), favouring vegetated and pioneer environments, respectively. The study was conducted across six areas of ca. 250 km 2 each. Mixed effect models were used to determine which landscape features affect the genetic diversity of the two species. These analyses were performed at three time points (1940s, 1970s and 2000s). Genetic diversity of B. bufo was found to increase with the area of semi-wooded and herbaceous vegetation, and decrease with the area of roads and urbanized areas. Genetic diversity of B. calamita increased with the area of bare ground and of quarries, and decreased with the area of dense woods. We found no effect of quarrying on B. bufo , unlike for B. calamita in which genetic diversity was favoured by quarrying at all three time-points. Despite having similar generation times, B. bufo ’s diversity was best explained by 1940s landscape and that of B. calamita by 2000s landscape. This study enlightens the genetic conservation value of quarries for pioneer species and the possible delays between landscape changes and their effects on the populations of some, but not all, species.