Molecular Characterization of Local Adaptation of Natural Flowering Dogwood Populations (C. florida) to Fungal Pathogens and Environmental Stress

Pais, Andrew

ABSTRACT: Next-generation-sequencing and untargeted metabolite markers offer promising contributions for the study of natural diversity at the genetic, phenotypic, and species level. In particular, the study of ecologically valuable non-model systems has advanced because of the rapidly decreasing costs to obtain large high-quality genomic data for many biological replicates. In the presence of both natural and anthropogenic changes to the environment, evolutionary ecologists are able to better characterize and monitor the health of natural populations via estimates of genetic diversity, phenotypic diversity, and quantitative measures of abiotic-biotic pressures. In the study of the flowering dogwood tree (Cornus florida L.), the focal species of this dissertation, innovations in the collection and analysis of molecular marker data have aided in identification of specific genomic regions that may be responsible for or associated with functionally adaptive traits. Phytochemical traits, which are important to plant defense and interaction with other organisms, can now be characterized with high-throughput LC-MS methods for studying the influence of ecological pressures (e.g. abiotic stress and fungal pathogens) on plant health and secondary metabolism, relationships of genetic and phytochemical diversity, and the ecology of pathogen-host and herbivore-plant relationships. We are interested in how natural populations of flowering dogwoods have responded to different environments including variable degrees of soil leaching, heat-light intensity, and drought as well as different assemblages of fungal foliar pathogens within the phyllosphere of C. florida (inside and on leaf surface). Additionally, I have tested the effects of genetic variation and environmental factors on phytochemical diversity (measured by untargeted metabolomics profiling). Among sampled populations facing varying abiotic-biotic selective pressures, I have found highly differentiated alleles putatively under positive selection and chemical biomarkers predictive of plant health and disease. The patterns of genetic and chemical variation, candidate loci under selection, and chemical biomarkers represent new discovery and evidence of local adaptations in C. florida. The evidence provided will inform conservation and future ecological-genomic research on the flowering dogwood tree. By prioritizing the conservation of genetic diversity in natural populations of C. florida, intraspecific functional diversity may be preserved along with biodiversity associated with the species.