Fig. 4: Hypothesized three stages of epigenetically associated Astatotilapia ecomorph speciation in Lake Masoko.
From: Epigenetic divergence during early stages of speciation in an African crater lake cichlid fish
(1) Colonization of the shallow habitats of Lake Masoko by the generalist riverine Astatotilapia population approximately 10,000 years ago (Malinsky et al.16). (2) Occupancy of shallow, reedy and highly oxygenated habitats by fish with a high level of depth philopatry. Phenotypic plasticity, partially linked to global methylome changes, enables utilization of littoral macroinvertebrate prey. (3) Colonization of deep, zooplankton-rich and lowly oxygenated habitats by the shallow population approximately 1,000 years ago (Malinsky et al.16). Extreme methylome changes in the benthic population associated with diet (for example, fatty acid metabolism) and environment (for example, hemoglobin composition) are shown. Epialleles are reciprocally fixed in the two populations, plausibly leading migrants, and those of intermediate epi-genotypes, to suffer a fitness disadvantage. Eventually, selection leads to differential fixation of genomic variation.
