Bigelow's Tansyaster (Dieteria bigelovii (A.Gray) D.R.Morgan & R.L.Hartm.)

Also classified as Machaeranthera bigelovii (A. Gray) Greene.

POWO and BONAP both list Machaeranthera bigelovii (A. Gray) Greene as a synonym of the specific subvariety Dieteria bigelovii var. bigelovii and not the species itself. However, those other two varieties already had been classified under that old species name, and both schemes have a total of three varieties with a 1-1 correspondence between them. This is one of many instances where commonly-used conventions of plant taxonomy obfuscate, rather than clarify, the relationships between the taxa in question. The 1-1 correspondence is between Machaeranthera bigelovii and Dieteria bigelovii, and the relationship between the taxa described by the names Machaeranthera bigelovii (A.Gray) Greene, and Dieteria bigelovii var. bigelovii, is one of containment.