A sample of floral variation in Eriastrum:

E. diffusum.  The photo on the far right is probably E. eremicum subsp. yageri.

E. sapphirinum subsp. dasyanthum, at least, people think they’re all the same thing.  The photo on the far right is E. virgatum.

Diagram of corolla distance measurements from a pilot study.  Measurements in red were significantly different between E. tracyi and E. brandegeae (Mann-Whitney U test, p≤0.05).