Meeting Abstract
The pharyngeal jaw (PJ) apparatus is important for prey processing in fishes, and variation in this structure is associated with species divergence into distinct foraging niches. Differences in PJ shape are typically studied within the context of broad ecological niche-shifts (e.g., molluscivore vs piscivore). Comparatively little is known about patterns of variation in this structure within a foraging niche. In this study, we examined PJ morphology in two herbivorous cichlid species from Lake Malawi, Labeotropheus fuelleborni (LF) and Maylandia zebra (MZ). We detected measurable differences for a range of PJ traits, which suggests that species with broadly overlapping diets have distinct PJ shapes. We next assayed the same phenotypes in an F2 population generated from crossing LF and MZ, which enabled us to genetically map loci associated with variation in PJ shape (i.e., QTL analysis). In total, 42 QTL were detected. For most QTL the allele effects were in the expected direction, which is consistent with PJ evolution via divergent selection. There was also a fair amount of overlap between QTL for different PJ traits, including at least two “hotspots”. One of these hotspots contains the regulatory gene, ptch1, which has been previously associated with oral jaw divergence between LF and MZ. In all, we find that subtle PJ shape variation has a tractable genetic basis, which may allow for future investigations into the molecular mechanisms that underlie divergence in this important trait.
