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Habitat preferences, intraspecific variation, and restoration of a rare soil specialist in northern Nevada
AuthorMcClinton, Jamey D.
Environmental and Natural Resource Sciences
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Edaphic specialization in plants is associated with the development of novel adaptations that frequently lead to speciation, causing unique edaphic environments to be associated with rare and endemic plant species worldwide. These species contribute significantly to global biodiversity, but are especially vulnerable to disturbance and climate change because of their inherently patchy distributions and locally adapted populations. Successful conservation of these species depends upon understanding their habitat requirements and the amounts and distributions of genetic and phenotypic diversity among populations. Little is known about the habitat requirements or levels of genetic and phenotypic diversity of edaphic specialists in the Great Basin of the western United states. Therefore, to improve understanding of edaphic specialization in this region, and to create a foundation of knowledge for species conservation, we used phenotypic measurements in the field, greenhouse common garden studies, and next-generation genetic sequencing techniques to investigate the associations between soil variation and plant phenotypes, and between genetic and phenotypic diversity in Eriogonum crosbyae, a rare edaphic specialist on soils developed from hydrothermally altered volcanic ash in the north-western Great Basin. We found that soil properties were poor predictors of site occupation among outcrops of known or potential habitat in our study area, and that site occupation could change over time. E. crosbyae showed phenotypically plastic responses to soil variation in the greenhouse, and there were associations between soil properties and plant form in the field. Growth was generally better in relatively milder and more fertile field soils when grown without competition, and differences in seedlings’ ability to establish in different soil types may partially explain the species’ patchy distribution in potential habitat. Our genetic analyses revealed high levels of nucleotide diversity and the presence of three highly differentiated genetic groups that often co-occurred within individual sites. The distribution of these groups across the landscape may be consistent with periods of allopatric diversification and subsequent secondary contact. Phenotypic diversity varied more clearly among groups than among sites dominated by a single group, and this variation was more apparent in seedlings grown in the greenhouse than in mature plants measured in the wild. Further studies exploring growth responses to variation in individual soil properties and plant performance in the presence of competition would improve understanding of the mechanisms underlying edaphic specialization in this species. Additionally, more information on the evolutionary history and taxonomy of the genetic groups and how they relate to other edaphically specialized Eriogonum in this region would improve understanding of diversity in these unique edaphic habitats in the Great Basin. Our results highlight the potential for simple-seeming systems to contain significant levels of cryptic diversity, and suggest that caution is warranted when considering potential impacts to these unique habitats.