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
