The following Participating Institutions are custodians for this species in the CPC National Collection:
The Arboretum at Flagstaff
The conservation of Astragalus cremnophylax var. cremnophylax is fully sponsored.
Joyce Maschinski, Ph.D. contributed to this Plant Profile.
Sentry milk-vetch is a rock-hugging plant that literally grows in sites that overlook the Grand Canyon. It's scientific name means 'gorge watchman'. The population where this plant was first collected was threatened by trampling from the millions of visitors to Grand Canyon National Park. In 1990, the Park Service erected a fence to re-route traffic around the sentry milk-vetch. Since protection, this population has thrived, increasing in numbers 4-fold. New locations where plants grow along the rim have been discovered; one site has only 2 plants growing on a Kaibab limestone platform about the size of a dinner table. A second site, on the north rim of Grand Canyon, is fairly remote and free from trampling pressure. (Maschinski & Rutman 1993)
Distribution & Occurrence
This species grows on a white layer of Kaibab limestone with little or no soil in unshaded openings in the pinyon-juniper-cliffrose plant community (Maschinski & Rutman 1993).
Sentry milk-vetch grows in association with rock mat (Petrophytum caespitosum). (Maschinski & Rutman 1993)
|The three populations of this species are located within Grand Canyon National Park. Two known populations occur on the South Rim of the Grand Canyon, where one site has 2 living individuals and the other site has approximately 1000. On the north rim on several Kaibab limestone fingers jutting into the canyon, there are approximately 1500 individuals. The north rim populations are undergoing taxonomic scrutiny to determine if they are in fact the same variety. (Maschinski & Rutman 1993)|
Conservation, Ecology & Research
Low genetic variation
Poor seed production
(NatureServe Explorer 2002)
The Center for Research of Endangered Wildlife is investigating using tissue culture techniques to propagate sentry milk-vetch.
Reproductive success and the possibility of inbreeding depression in the wild populations is being investigated by Allphin et al. (in prep).
Allphin, L.; Weins, D.; Brian, N.J.; Randall, P. Reproductive success and genetic divergence among varieties of the rare and endangered Astragalus cremnophylax from Arizona, USA. (Oral presentation). 3rd Southwestern Rare and Endangered Plant Conference;
Harrington, H.D. 1964. Manual of the plants of Colorado. Chicago, IL: The Swallow Press Inc. 666p.
Maschinski, J. Integrated conservation strategies for recovery of Astragalus cremnophylax var. cremnophylax at the South Rim of Grand Canyon National Park. First Biennial Conference on Research at Flagstaff; 1991; Flagstaff, AZ.