Figure 1

Sampling locations in France. Both C. elegans and C. briggsae were found in the locations where extensive sampling was performed (large disks), except in the Western France (Plougasnou) location. Locations with names in black are those in Table 1. Others are from [9, 52] or new locations that have been only occasionally and sparsely sampled (small symbols and fonts) (Credits: Bergerac: Victor Nigon [53]; Buzançais: Jean-Baptiste Pénigault; Marseille, Nice, Antibes: Christian Braendle).