DISSERTATION RESEARCH: Developmental mechanisms of morphological novelty and adaptation in the hindlimbs of bats (Chiroptera)

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This project seeks to better understand evolutionary novelty and anatomical diversity through an investigation of the bat calcar, a skeletal element found in bat feet but not in the feet of other mammals. The calcar is a 'neomorphism,'it suddenly appears in the earliest bats but is not found in their ancestors: its appearance in the fossil record is difficult to explain. The bat calcar is particularly exceptional because it varies extensively across bat species, suggesting that anatomical variation may have functional and ecological implications. Therefore, the calcar offers a unique model system for studying the processes that generate anatomical novelty and diversity in vertebrates. In this project, the researchers will link approaches from developmental biology and biomechanics in order to explain the evolution of the calcar and to explore its functional relevance across the global radiation of bats. The researchers will also create education and outreach activities that will promote the utility of interdisciplinary research for solving enduring questions in biology.The researchers' primary goal is to use the calcar of bats (Chiroptera) to understand how developmental modifications can lead to the formation of novel skeletal structures and to functionally-relevant variability in those structures. The specific objectives of this project are to 1) reveal the developmental origin of the calcar and discern its homology among bats, and 2) identify developmental processes that lead to differences in connective tissue composition among calcars (i.e., why some calcars calcify or ossify while others do not). These objectives will be addressed using histochemical and immunofluorescent assays of bat embryos representing phylogenetically, morphologically, and ecologically diverse species. These experiments will expand on the researchers' recent work on calcar functional anatomy and biomechanics. This project will strengthen the ability of the researchers to test their overarching hypothesis: the evolution of the calcar resulted from modifications in developmental regulation of chondrogenesis and ossification leading to adaptive evolution.