Meeting Abstract

144.4  Monday, Jan. 7  Developmental and genetic basis of a morphological novelty in East African cichlids CONCANNON, M.R.*; ALBERTSON, R.C.; UMass Amherst; UMass Amherst mrconcan@cns.umass.edu

The production of novel phenotypic variation provides new traits on which selection can act and is often associated with expanded ecological opportunity. For this reason the developmental and genetic origins of phenotypic novelty are key questions in evo-devo research. The massive adaptive radiation of East African (EA) cichlids is most commonly associated with convergence, but there are also several instances of novelty that have evolved in this group. Craniofacial variation is a major axis of divergence among EA cichlids, and a species at the far end of the phenotypic spectrum, Labeotropheus fuelleborni (LF), has an enhanced facial feature of unknown form and function. This novelty is a fleshy elongated snout (‘flap’) that rests on the upper jaw, and is absent from any other cichlid, including a phenotypically similar ecological competitor, Tropheops red cheek (TRC). We analyzed flap development in both species and found that it begins to diverge relatively late in development when fry are about 1.4 cm in standard length, at which point the flap continues to grow isometrically in LF and plateaus in TRC. We also generated an F2 hybrid mapping population from a cross between LF and TRC, and a high-resolution linkage map in order to perform quantitative trait loci (QTL) mapping for flap size. We identified three significant QTL, which is consistent with our estimated number of loci (Castle-Wright estimator = 4-5 factors). Further, our QTL model is consistent with both a dominant and additive mode of inheritance, with little evidence for epistasis. Given these data and the tractability of this system, we are poised to identify the specific genetic loci and developmental mode of action involved in the evolution of this trait as well as a foundation for its ecological and biological significance.