The genomic architecture of convergent snail crushing jaws in cichlid fishes

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Convergent phenotypes that arise during adaptive radiation could often result from similar changes in genomic architecture. The goal of this proposal is to test hypotheses regarding the genomic architecture of convergence in crushing pharyngeal morphology in several lineages of cichlid fish. The outlined approach integrates mapping of the position of genomic regions affecting traits such as tooth size, muscle mass, and jaw suturing within the genome. The proposal addresses three major questions:Objective 1: What genomic region(s) are associated with the polymorphism in tooth size found in H. minckleyi? Using a hybrid F2 mapping cross, we will determine if there is a single locus of large effect or alternatively multiple regions of the genome associated with bimodal size of the pharyngeal teeth in H. minckleyi. Objective 2: Do the QTL for other pharyngeal jaw traits associated with the tooth size polymorphism in wild-caught H. minckleyi co-localize to tooth size QTL? We will use the QTL identified in Objective 1 to determine if QTL identified for other pharyngeal jaw traits associated with the molariform versus papilliform tooth size dichotomy co-localize to homologous regions of the genome where tooth size QTL(s) are present. We will also evaluate whether the genomic architecture for these additional traits themselves are exceptionally co-localized to similar regions of the genome.Objective 3: Is the genomic architecture associated with the crushing phenotypes in other cichlid lineages similar to that found in H. minckleyi? We will use four additional hybrid crosses of species that differ along a molariform to papilliform axis to determine if species pairs that span cichlid diversity exhibit the same number of QTLs, same degree of co-localization, as well as QTL in the homologous genomic locations that we recovered for the pharyngeal jaw divergence in polymorphic populations of H. minckleyi.The QTL studies performed in a number of lineages that have diverged along a similar phenotypic axis should provide a test of whether similar or very distinct genomic loci have generated pharyngeal jaw convergence within populations and across species of cichlid fishes.