Penstemon luculentus R.L.Johnson & M.R.Stevens, 2016

Johnson, Robert L., Stevens, Mikel R., Johnson, Leigh A., Robbins, Matthew D., Anderson, Chris D., Ricks, Nathan J. & Farley, Kevin M., 2016, Molecular and morphological evidence for Penstemon luculentus (Plantaginaceae): a replacement name for Penstemon fremontii var. glabrescens, PhytoKeys 63, pp. 47-62 : 48

Penstemon luculentus R.L.Johnson & M.R.Stevens nom. nov.

Penstemon luculentus R.L.Johnson & M.R.Stevens, nom. nov. ≡ Penstemon fremontii Torr. & A. Gray var. glabrescens Dorn & Lichvar, Madroño 37(3): 195-199, f. 1, 2 [map]. 1990. (non Penstemon glabrescens Pennell in Contributions from the United States National Herbarium 20: 375-376. 1920). Type: USA. Colorado: Garfield Co, Douglas Pass, 8000 ft., 7 July 1987, R. Dorn 4656 (holotype RMS!).

Note.

Elevating Penstemon fremontii var. glabrescens to a species using the epithet glabrescens was not possible because Penstemon glabrescens is already occupied ( Pennell 1920).

Etymology.

Penstemon luculentus is derived from the Latin " luculentus ," meaning brilliant or bright. The name was chosen to reflect the brilliant blue flower color, which is particularly striking in the field contrasting against the whitish or tan shale background typically associated with the species (Fig. 1A, B ).

Remarks.

Penstemon luculentus (≡ Penstemon fremontii var. glabrescens ) grows almost exclusively on steep slopes composed of Green River shale or sometimes intermixed with sandstone fragments from overlying strata. It is locally common on road cuts. It occurs primarily within the Piceance drainage with populations occurring abundantly on exposed shale along Piceance Creek and the adjacent tributaries, including the Yellow Creek drainage in Rio Blanco Co., CO. (Fig. 2 ). It also occurs on shale slopes of the Roan Creek drainage in Garfield Co., CO. The Colorado Natural Heritage Program (CNHP) gives this taxon a global rank of G3G4T2 and a state rank of S2 due to threats from gas and oil drilling throughout its habitat in the Piceance Basin ( CNHP 2015). The ranking of G3G4 indicates a status between vulnerable and apparently secure. The rank of S2 specifies a state status of "imperiled - at high risk of extinction due to very restricted range, very few populations (often 20 or fewer), recent and widespread declines, or other factors" ( Rondeau et al. 2011). Currently oil and gas drilling have not had a noticeable impact on its populations, but that could change if oil extraction begins to include the mining of oil shale.

Figures

Figure 1. A Penstemon luculentus in its commonly found native whitish or tan shale habitat B An individual Penstemon luculentus plant growing in its typical shale habitat.

Figure 2. Map showing known distribution of Penstemon luculentus in Rio Blanco and Garfield counties Colorado.