A Population Genetics Study of Rhododendron smokianum

Spears, Tara

ABSTRACT: The Great Smoky Mountains National Park (North Carolina/Tennessee, USA) is one of the most biodiverse places in the United States, with 19,000 species documented and an estimated tens of thousands more predicted to inhabit the 816 square miles of protected land. Scientists are continually studying the Park’s biodiversity, and the identification and delineation of species is important for how biodiversity is categorized for different management practices. Rhododendron smokianum, a newly described species of Rhododendron endemic to the Park, has not been sampled across its range, and lacks a comprehensive molecular genetic analysis to determine if it merits species status. Here we present a population genetic analysis of R.smokianum using RAD-seq, along with field observation and analysis. Using genome-level analyses of 44 putative R. smokianum specimens with four outgroup members of Rhododendron minus Subsect. Caroliniana–from which this species is derived–we assessed relative genetic diversity of R. smokianum to determine if the group merits distinction as a separate species. We found that genetic diversity specific to R. smokianum is consistent across all samples. There is some shared genetic diversity with the outgroups, but these are likely the result of hybridization or shared ancestry. Field observation and occurrence mapping revealed that R. smokianum grows on the Anakeesta and Thunderhead Sandstone Formations, and one occurrence possible on the Copperhill Formation. Our results support the separation of R. smokianum into a distinct species, describe its population genetic structure, and present additional element occurrences and geological occurrence information. This information can guide management practices for R. smokianum within Great Smoky Mountains National Park.