Mentzelia humilis var. guadalupensis
(Guadalupe stickleaf)
[taxon report][distribution map][photos][line drawing]
Family: Loasaceae
Scientific Name: Mentzelia humilis (A. Gray) J. Darlington var. guadalupensis Spellenberg
Synonyms: None
Vernacular Name: Guadalupe stickleaf
R-E-D Code: 3-1-3
Description: Densely tufted perennial 5-25 cm tall, covered with minute, harsh, retrorsely barbed hairs that give the surface the texture of shark skin or a cat's tongue; basal leaves spatulate, dentate, with 2-4 teeth per side, or sometimes the smallest leaves nearly entire; midstem leaves 3-8.5 cm long, 8-21 mm wide, the blade spatulate or lanceolate in outline, tapering gradually to a slender petiole, the blade from shallowly to deeply dentate or pinnatisect, 3-7 teeth or lobes per side, when pinnatisect or deeply dentate the rachis 2-8 mm wide and the lobes straight or sometimes falcate, tapering from base to acute tip; inflorescence congested; flowers symmetrical, petals about 10, white or pale cream when fresh, 10-13 mm long, intergrading with outer stamens (which have broad filaments); capsule cupulate, 5-8 mm long, 5-6 mm wide, the calyx lobes on capsules narrowly triangular-subulate; seeds narrowly winged. Flowers July through September.
Similar Species: Mentzelia humilis var. humilis differs in its entire leaves, or leaves that are pinnately lobed with lobes that have parallel edges and a rounded tip. Other Mentzelia in the region have larger flowers, flowers that are yellow when fresh, capsules that are proportionately longer, or the plants are not densely clumped.
Distribution: New Mexico, southeastern Otero County, west slope of the Guadalupe Mountains.
Habitat: Open gypsum outcrops of the Yeso Formation, with limestone cobble, at about 1,350-1,550 m (4,425-5,080 ft).
Remarks: This plant is locally abundant within its restricted habitat, a series of gypsum outcrops that occur for about a dozen kilometers on the west face of the northern portion of the Guadalupe Mountains. Its closest relative, Mentzelia humilis var. humilis, occurs east of the Guadalupe Mountains, also on gypseous soils.
Conservation Considerations: Guadalupe stickleaf is highly restricted geographically, in part because of edaphic specificity. Ranching activities on Crow Flats, the valley to the west of the populations, do not affect the species because, as one rancher noted, cattle do not go onto its habitat. Water sources are distant. No impact on these plants by domestic or wild animals have been noted.
Important Literature (*Illustration):
Darlington, J. 1934. A monograph of the genus Mentzelia. Annals of the Missouri Botanical Garden 21:103-222.
Spellenberg, R. and T. Wootten. 1999. Vascular plants on a gypsum outcrop in southern New Mexico: A listing, a new variety and taxonomic realignments in the Anulocaulis leiosolenus complex (Nyctaginaceae), and a new variety of Mentzelia humilis (Loasaceae). Sida 18(4):987-999.
Thompson, H.J. and A.M. Powell. 1981. Loasaceae of the Chihuahuan Desert region. Phytologia 49:16-32.
Information Compiled By: Richard Spellenberg, 1999
Agency Status:
