Abstract
Penstemon luculentus R.L.Johnson & M.R.Stevens, nom. nov. replaces Penstemon fremontii var. glabrescens Dorn & Lichvar. The varietal name glabrescens was not elevated because it was already occupied by Penstemon glabrescens Pennell, a different species. This new arrangement is supported by molecular and morphological evidence. An analysis of genetic diversity in populations of both varieties of Penstemon fremontii Torr. & A. Gray (glabrescens and fremontii) from the Piceance Basin, Colorado, using SSR (simple sequences repeats) or microsatellites markers, revealed significant genetic differentiation between the two. Penstemon fremontii var. glabrescens was also genetically different from Penstemon gibbensii Dorn and Penstemon scariosus var. garrettii (Pennell) N.H. Holmgren. The combination of hirtellous stems, glabrous leaves, non-glandular inflorescence, and long anther hairs distinguish Penstemon luculentus from other morphologically similar species.