DISSERTATION RESEARCH: The species versus subspecies conundrum: quantitative assessment from integrating multiple data types under a single Bayesian framework in Hercules beetles

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Are there differences in how species and subspecies are designated among different groups of organisms? If so, surveys of biodiversity could be biased, potentially either under- or over-estimating levels of species diversity. Researchers will address this issue using genetic and morphological data from two groups of Hercules beetles (genus Dynastes), where diversity patterns differ between North and South America, perhaps because of differing applications of species versus subspecies designations. Through quantitative assessments of the observed differences among taxa, researchers will test if genetic and morphological differences between species are more pronounced than those found among subspecies. Knowledge gained by this research will demonstrate how taxonomy can be assessed consistently, objectively, and quantitatively across distinct groups of organisms and between geographic regions. Such a standardized approach is critical to avoiding potential biases in biodiversity surveys of species diversity and the identification of taxa in need of conservation. One graduate student will be trained in diverse systematic methods and a website will be established to broadly disseminate the species delimitation methods developed by the researchers.While considerable recent research has focused on quantitative methods for objectively delimiting species, an overlooked, but equally important, issue regards the nature of the taxonomic entities being delimited. A model-based approach will be applied to test whether species and subspecies of Hercules beetles are statistically equivalent. Researchers will also test if currently recognized taxa represent different points along the speciation continuum and whether levels of differentiation fit with expectations based on the time taxa have been diverging. Because both phenotypic and genetic data will be analyzed in a Bayesian framework, the research will be able to determine whether disagreements in species boundaries among data types reflect (i) discordance with the actual history of lineage splitting, or (ii) differences in the amount of time required for differentiation to become apparent among the taxa in different data types (specifically, different rates of evolutionary change in genetic versus morphological data). This work advances biodiversity studies by making it possible for the theoretical view of speciation as a continuous process to be applied in practice in a quantitative manner such that the taxonomic equivalent units of biodiversity can be determined for comparisons of species diversity in different geographic regions and across different groups of organisms.