Controlled crosses
From the wild-collected larvae, 74 females and 69 males (F0 generation) were used to establish 66 North x South crosses, producing the F1 generation (Supp. Fig. 1). A total of 92 female and 69 male F1 beetles were used to establish 66 full-sibling crosses, producing the F2 generation (Supp. Fig. 1). Of these full-sibling crosses, 22 (33%) failed to produce offspring and 10 (15%) produced three or fewer offspring. A further 20 (30%) of these F1 families were discarded due to insufficient brood size (<10 individuals) or evidence of gallery mixing (i.e., clear family units could not be identified). Thus, 14 (21%) F1 broods remained for producing an F2 generation. A total of 17 F1 and 212 F2 individuals were genotyped (N=229), while ten F1 specimens (nine males and one female) that were parents of the F2 broods were not recovered from their bolts (Supp. Tab. 3).