Ecological Adaptation and Speciation: The Evolutionary Significance of Habitat Avoidance as a Postzygotic Reproductive Barrier to Gene Flow

Figure 2

Illustration of model 2 based on epistasis between habitat preference and avoidance loci. Numbered steps of model (1–4) are separated by dashed lines and ordered vertically. Individuals are represented by chromosome pairs as grey bars; preference locus (on left) and avoidance locus (on right) are marked by two pairs of vertical black tick marks on grey chromosomes. Alleles at preference locus are labeled as follows: 𝑎⁺: preference for ancestral habitat; 𝑛⁺: preference for novel habitat. Alleles at avoidance locus are labeled as follows: 𝑛⁻: avoidance for novel habitat; 𝑎⁻: avoidance for ancestral habitat. Arrow depicts shift from ancestral habitat 1 to novel habitat 2.