Chloroplast Studies in Sagebrush

Big sagebrush (Artemisia tridentata), dominates the landscapes of the western United States—it is the most common shrub in the West, covering 8.7 million ha of the Great Basin. However, despite its ubiquity, taxonomic identification of big sagebrush subspecies has been a source of contention among botanists. Debate stems from variation in morphological characters caused by polyploidy and hybridization. A traditional method of constructing phylogenies in plants is by building relationships from targeting the plastid genome. However, both species of Artemisia and subspecies of Artemisia tridentata lacked a strong phylogenetic signal based on 40 amplicons of the Artemisia chloroplast. The signal is further complicated because the amplicon data suggest evidence of heteroplasmy in Artemisia. Extraction and de novo assembly of whole chloroplast genomes may reveal a stronger phylogenetic signal not previously revealed by targeted enrichment. It may also reveal the presence or absence of heteroplasmy. Accurate phylogenies can then be used to better understand hybrid relationships between species and subspecies of Artemisia. An understanding of the complex evolutionary relationships and processes of polyploidization in Artemisia tridentata and related species would provide a foundation for developing restoration plans needed to sustain sage grouse and other wildlife species.