Evolution and development of skeletal patterning

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The research program will examine the developmental and evolutionary biology of the vertebrate skeleton across large scale evolutionary transitions. Specifically, it will explore the interplay between developmental and evolutionary integration and variation in the skeleton across the fish to tetrapod and dinosaur to bird transitions using quantitative methods of shape description and gene expression. The two transitions are chosen because of their rich fossil record and wealth of developmental biology of relevant extant species. A set of complimentary projects are designed to bridge a broad interdisciplinary program that researches a spectrum from genetic evolution, to developmental mechanics, to biological imaging and quantitative phenomics, to evolutionary patterns, rates, and variation. Research will focus on the development and evolution of paired appendages (fins and limbs) and the axial column (spine and tail). Both have undergone dramatic evolutionary changes across the fish-tetrapod and dinosaur-bird transitions and are expected to have had equally dramatic developmental changes. The first phase of projects will reconstruct the evolutionary changes of these anatomies across these two transitions. This will be done by adding qualitative and quantitative data to existing datasets to estimate rates and types of anatomical evolution at these transitions. The second phase will image the skeletal development (from undifferentiated mesenchyme, to condensations, to chondrified, and then ossified bone) of the endoskeleton of these two anatomical regions in extant embryos of selected fishes, amphibians, mammals, reptiles, and birds. This imaging will make intensive use soft tissue imaging with a new nano-focus micro CT machine under my supervision recently awarded in a CFI Innovation Fund (PI: Vogel, An integrated quantitative biology initiative [IQBI]). The third phase will test for genetic and epigenetic (environmental) control of early stages of skeletal patterning in these regions. Some results are expected to highlight developmental switch points that may be associated with rapid rates of evolutionary change whereas others may highlight developmental conservation. This research will derive a working model of skeletal development and evolution. The results will have application to our understanding of how biological systems evolve and how developmental biology influences large scale evolutionary change. Other applications are the development of an efficient work flow for imaging, quantifying, and comparing anatomical data. This has enormous implications for objectively estimating evolutionary relationships, describing developmental variation, and medical imaging.