San Rafael cactus
[Pediocactus bradyi subsp. despainii (S.L. Welsh & Goodrich) Hochstätter, more]
Plants typically unbranched. Stems subglobose to obovoid, 3.8-6 × 3-9.5 cm; areoles circular to oval, villous to glabrate. Spines smooth, relatively hard, all radial, 9-15 per areole, spreading, white, 2-6 mm. Flowers 1.5-2.5 × 1.8-2.5 cm; scales and outer tepals minutely toothed to entire and undulate; outer tepals yellow-bronze to peach-bronze or pink with purple midstripes, 4-10 × 3-6 mm; inner tepals yellow-bronze to peach-bronze (rarely pink), 6-12 × 4-6 mm. Fruits green, drying reddish brown, turbinate, 9-11 × 10-12 mm. Seeds black, 3.5 × 2.5 mm, shiny, papillate and rugose. Flowering spring. Desert pavements of cobble or pebble in pinyon-juniper woodlands; of conservation concern; 1500-1800 m; Utah. Population-level studies of chloroplast DNA (J. M. Porter et al. unpubl.) confirm a close relationship between Pediocactus despainii and P. winkleri. Genetic relationships among populations correspond to geographic features of the region: populations with the San Rafael Swell represent one group of related populations, and populations south of the San Rafael Swell represent another group of related populations. This pattern conflicts in some ways with morphology. While all of the populations south of the San Rafael Swell are classified as P. winkleri, within the Swell some populations are P. despainii, several are P. winkleri, and a few are morphologically intermediate.
Addendum: Since the above was published, plants that are a good match for P. despainii have been found just barely into northwestern Wayne County, S/SW of the primary range of the species. Global distribution of this species is therefore in Emery and Wayne Cos. in Utah. These plants are nonetheless still remote from plants recognized as P. winkleri. So the dividing line between the species in part may be from west to east with P. despainii tending to occupy somewhat higher elevation sites and in somewhat different plant community rather than simply north to south. Cacti in most genera tend to readily hybridize when they come into contact with one another, so morphologically intermediate plants would be expected. While known elevational range is in the 1450m to 1800m range as reported, plants are also known from as high as almost 2075m. Plants tend to flower later than P. winkleri.
This project made possible by National Science Foundation Award 1410069