Erigeron bistiensis Nesom and Hevron


Family: Asteraceae

Description: Caespitose, perennial herbs in clumps up to 30 cm in diameter. Stems erect (7-15 cm) unbranched, gray green. Leaves gray-green. Heads terminal, solitary, radiate. Ray florets in a single series, white, drying white or pinkish to bluish, distinctly coiling with maturity.

Distribution: Nesom and Hevron (1995) describe E. bistiensis from a single population of 200-250 plants scattered over 3-4 acres in San Juan County (See type locality below). However, specimens determined by R.C. Sivinski are from other parts of San Juan County (see next section for locations) as are two populations recorded by the Navajo Natural Heritage Program: E of SR 44 and W side of Horn Canyon (Daniela Roth, personal communications).

Plants seen or cited: (holotype: UNM; isotypes: ARIZ, ASC, ASU, BRY, COLO, NMC, NY, TEX, UC, US, UT, UTC). R.C. Sivinski at UNM 3663 (Angel Peak Badlands), 3666 (E of Bloomfield), and 3781 (S side of Aztec). Heil 8433 (at or close to type locality).

Type locality: San Juan County: Navajo Indian Reservation. San Juan Basin NE of Bisti Trading Post. Elevation 6340 ft. Most plants past flower or near it. 5 June 1993. Collected by Bill Hevron.

Comments: Nesom and Hevron (1995) described E. bistiensis from the only known population in San Juan County. If it is a distinct species, E. bistiensis is likely the rarest Erigeron in New Mexico. However, the above publication did not describe the relationship of this species to the more common E. pulcherrimus Heller. I have concluded that E. bistiensis is not distinct from E. pulcherrimus that is common in New Mexico, Colorado, Utah, and Wyoming (Tonne 1999).

Conservation Considerations: I have included Nesom and Hevron's (1995) assessment of the threats to E. bistiensis:
"There are no signs of predation, herbivory or disease on Erigeron bistiensis. Grazing is intense in the area of the type locality, but livestock do not appear to pose a threat to the continued existence of the species, which appears to be relatively unpalatable. Oil and gas extraction, with associated road construction, represents the other major land use and may pose a significant threat. Based on its small population size and current threats, E. bistiensis will be proposed for listing under the Endangered Species Act."

Important Literature:

Nesom, Guy L. and Bill Hevron. 1995. Erigeron Bistiensis (ASTERACEAE: ASTEREAE): A New Species from Northwestern New Mexico. Madrono 42(1):12-18.

Tonne, Phil. 1999. A morphometric analysis of Erigeron pulcherrimus, Erigeron bistiensis, and related Erigeron species. M.S. Thesis, University of New Mexico Biology Department, Albuquerque, New Mexico.

Information Compiled By: Phil Tonne, 1998; updated 2007