CAREER: Flexibility, constraints, and selection in repeated ear loss and regain in toads

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Most frogs and toads vocalize to communicate, and females typically use hearing to locate mates. Despite how essential tympanic ears are for hearing sound in air, outer and middle ear structures have been lost and regained many times in frogs and toads. This project integrates anatomy, physiology, development, and phylogenetic analyses to investigate the independent gains and losses of ear structures. Relating ear morphology to hearing ability will reveal novel mechanisms of hearing and will characterize the costs and benefits of various anatomical features for hearing low and high pitch sounds. Because the development of ear structures is linked to the development of other skull features, this project will identify changes in the size and shape of skull bones that accompany changes in ear structures. Moreover, developmental analyses will determine specific genetic and cellular changes that cause the loss of outer and middle ear structures, a type of ear defect that is a common cause of human deafness.Integrative analyses of skull features will assess whether associated changes in skulls facilitate the diversity of ear structures, with data publicly available at Digimorph (http://www.digimorph.org/) and the CSU Digital Repository (http://lib.colostate.edu/repository/). The research in this proposal includes natural opportunities to better educate the general public and university students about hearing, biodiversity, and conservation. Within the US, this proposal will be integrated into undergraduate classes as part of a new laboratory approach to teach students to conduct and interpret statistical analyses. In addition, US undergraduates will participate in the research efforts and participate in developing a bilingual museum exhibition about frogs that will be displayed at one or more US science museums. The Ecuadorian toad breeding program and a related Ecuadorian museum exhibition will contribute to amphibian conservation at a key moment when road-building and resource extraction threaten to have major impacts on wildlife in Ecuador.