Group-based structure of the large pine weevil larvae. Description of the 5 group-based structures defined for the two population genetic approaches. Rectangles: regions. Circles: host-plant groups; P = Pine, S = Spruce; sample size in parentheses. Structure 1: individuals were grouped according to their geographic origin: Finland, Limousin, Ardèche, and Landes (the four rectangles 1, 2, 3, 4). Structure 2: individuals were grouped according to their geographic origin and host-plant (7 circles) Structures 3, 4, 5: within each of the three regions (rectangles 1, 2, 3) where both alternative host-plants are found (Finland, Limousin, and Ardèche), pairwise comparisons of host-plant samples were performed. Two circles in rectangle 1, 2, 3 correspond to structures 3, 4, 5 respectively.