DISSERTATION RESEARCH: Phenotypic plasticity and evolution in the pharyngeal jaw apparatus

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Phenotypic plasticity, developmental change within genetically similar individuals in response to environmental stimuli, could be a key feature in biological diversification. Cichlid fishes are an exceptionally diverse group that also might be unusually phenotypically plastic. This work is investigating the evolutionary consequences of phenotypic plasticity in morphology, gene expression, and evolution of protein-coding genes in these fishes. The current work is focused on a group that exhibits two alternative morphologies in the same populations that differ extensively in jaw characters. This type of variation could represent an intermediate stage in how evolutionary divergence begins, and species with this type of polymorphism might generally be more plastic than non-polymorphic species. Plasticity in the jaws of these fish will be examined using experimental manipulations of diet. Changes in the level of gene expression in the jaw muscles in response to diet will be quantified using high-throughput sequencing and compared to gene expression in a non-polymorphic species. These analyses will shed light on whether gene expression in a polymorphic species is greater than plasticity in gene expression in a less variable species. This project will produce broad insight into the origin and pace of morphological divergence among species. This work will also provide a better understanding of the molecular pathways involved in muscle growth and atrophy that are shared across all vertebrates. Students will be trained, and K-12 outreach will occur.