Arrival of the fittest: examining the underlying mechanisms of morphological plasticity in an adaptive radiation

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Studentship strategic priority area: BiodiversityKeywords: Evolution, plasticity, gene expression, boneAbstract: Phenotypic plasticity currently drives contentious debate in evolutionary biology. This debate deals with the role of environmental cues in generating biodiversity, species, and ultimately the utility of the standard Darwinian synthesis (or its extension). While plasticity is a topic of much empirical research with growing relevance to environmental change, we still lack a general understanding of the underlying mechanisms of plasticity in evolutionary systems. This studentship will draw on knowledge from bone biology to fill this gap, specifically focusing on how bones interpret the mechanosensory stimuli that instruct their growth and produce adaptive variation. A central dogma in bone biology is that osteocytes (mechanosensory cells) are the sole mechanism for bone to respond to mechanical stress. However, not all animals with bones possess osteocytes (most fishes having lost them), and there are emerging alternatives which our preliminary data point toward. Specifically, our previous research has identified variation in the magnitude of bone plasticity between related species of African cichlids. Cichlids are an exemplary system for evolutionary biologists in that they are derived from a recent common ancestor but exhibit vast amounts of adaptive skeletal variation. This variation appears to be controlled by a few mutations on a common genetic background. So far we have combined plasticity experiments with QTL mapping approaches to identify a number of candidate 'plasticity genes' in the craniofacial skeleton. These genes include members of signalling pathways previously implicated in bone development (Wnts, BMPs, FGFs), and structural genes including rootletin - a key component of the primary cilia and representative of a potential alternative mechanism for mechanosensory function. These findings provide a strong basis for understanding the molecular and cellular mechanisms involved in plasticity and their contribution to evolution.