Is it rare or common? Determining the phylogenetic position of Mirabilis rotundifolia, a potentially rare and endemic species in South Central Colorado

Mirabilis rotundifolia (Greene) Standley, or roundleaf four o’clock, is a perennial wildflower in the Nyctaginaceae family,  with ascending hairy stems, oval or round leaves, three purple flowers and pale olive green hairy fruit.  It is restricted to carbonate shale of Niobrara Formation found only in limited areas in the Arkansas River Valley in Pueblo and Fremont Counties in South Central Colorado. Given the limited distribution and proximity to development, M. rotundifolia is considered rare and threatened. Recently, the treatment by Richard Spellenberg in the Flora of North America discussed the potential that M. rotundifolia is merely a variant of the more widely distributed Mirabilis albida. We undertook a study using DNA sequence data to compare M. rotundifolia with the genus Mirabilis to examine its phylogenetic position and to determine if it is merly a variant of the more widespread M.albida. Understanding the phylogenetic position of M. rotundifolia will increase our knowledge of its taxonomic status and inform management decisions of this rare and endemic plant.