This is the second thistle from western North America to be featured on BPotD recently that is endemic to only one mountain or small mountainous area. Cirsium peckii, or Steens Mountain thistle, can only be found on Steens Mountain or the nearby Pueblo Mountains of Oregon. Cirsium clokeyi, on BPotD nearly two months ago, is endemic to the Spring Mountains of Nevada. When a pattern like this becomes noticeable, it is certain to catch the attention of botanists – and it has. Dr. Dean Kelch of the Baldwin Lab at the University of California, Berkeley, has investigated these narrowly-distributed endemics within Cirsium. Despite having low genetic diversity (by measure of rDNA), the Cirsium display an unusual amount of ecological diversity. The conclusions? Cirsium in North America have either undergone a rapid ecological radiation (meaning new species have evolved quickly to fill ecological niches) or the rDNA of thistles is highly conserved across species (meaning that as species of thistles evolve, this particular type of DNA does not change as much as it would typically be expected to do given the patterns in other plant groups). See: Kelch, DG and Baldwin, B. 2003. Phylogeny and ecological radiation of New World thistles (Cirsium, Cardueae - Compositae) based on ITS and ETS rDNA sequence data. Molecular Ecology. 12: 141-151.

Photographs of Cirsium peckii in flower can be seen here and here.