Figure 1: Illustration of model 1 based on intermediate null allele (see Table 1 for model description). Numbered steps of model (1–5) are separated by dashed lines and ordered vertically. Individuals are represented by chromosome pairs as grey bars; avoidance locus is marked by solid black tick mark on grey chromosome. Alleles at avoidance locus are labeled as follows: : preference for ancestral habitat; : recessive null allele (i.e., no preference or avoidance); : avoidance for ancestral habitat; : avoidance for novel habitat. Arrow depicts shift from ancestral habitat 1 to novel habitat 2.