Fig. 2.

Mapping of lower jaw mechanical advantage in cichlids. The QTL for relative height of the articular process (i.e., mechanical advantage of jaw closing, “MA-closing”) maps to LG21 and peaks over a marker on physical scaffold number 31 (A). A schematic of a primary cilium is shown in (A) as well, where “ax” is the axoneme, “bb” is the basal body, and “rt” illustrates the striated rootlet. The SNP at the QTL peak (red asterisk) encodes a nonsynonymous (A/V) polymorphism within Crocc2, where the A allele is conserved across African cichlids (B), and is associated with two predicted interruptions (arrowheads, C) in the heptad repeat (i.e., denoted, and color-coded, a–g). The V allele in LF is predicted to result in contiguous heptad repeats in this region of the protein (C). With additional markers every ∼0.5 Mb, we queried the phenotype–genotype relationship along scaffold 31, and show that the peak association remains at ∼2.9 Mb (red asterisk, D). We sought to refine the interval even further using markers every ∼100-200 kb, between ∼2–4 Mb on scaffold 31, and find that the peak association holds at the crocc2 SNP (red asterisk, D). Further, this marker is nearly alternatively fixed between -wild populations of LF and TRC (e.g., F_ST = 9.5).