Phylogeographic relationships within Packera sanguisorboides (Asteraceae), a narrow endemic species that straddles a major biogeographic boundary.

Packera sanguisorboides is endemic to the Sangre de Cristo and Sacramento Mountains of New Mexico, USA. As such, its distribution spans the boundary between two major floristic regions: the southern Rocky Mountain region and the Madrean region. Chloroplast DNA haplotype polymorphism patterns in populations from both regions show that most of the molecular variance exists among populations rather than between mountain ranges and that hybridization with at least one other Packera species containing distinct cpDNA haplotypes has contributed to the cpDNA diversity within P. sanguisorboides. Based on morphological and cpDNA data, the closest relatives to P. sanguisorboides are thought to be mesic species similar to P. glabella and P. sanguisorbae.