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-State Species Abstract-Wyoming Natural Diversity DatabaseYERMO XANTHOCEPHALUS
DESERT YELLOWHEAD
Family: Asteraceae
Status:
US Fish & Wildlife Service: Threatened
(2002).
Agency Status: Recognized as Threatened.
Heritage Rank:
Global: G1
State: S1
WYNDD Plant List: State Endemic (Very
High Conservation Priority)
Description: Desert yellowhead is a taprooted, glabrous perennial herb with leafy
stems to 30 cm high. The leathery leaves are
alternate, lance-shaped to oval, 4-25 cm long,
and often folded along the midvein. Leaf
edges are smooth or toothed. Flower heads
are numerous (25-180) and crowded
in a broad terminal inflorescence. Each head
contains 4-6 yellow disk flowers (ray flowers
are absent) surrounded by five yellow, keeled
involucre bracts. The pappus consists of
numerous white bristles (Fertig 1995).
Similar Species: Rayless species of
groundsel (such as Senecio hydrophilus and
S. rapifolius) can be distinguished by their
more numerous and green involucre bracts.
Dorn considers Yermo to be most closely
related to species of Cacalia, a genus native
to forests of eastern North America.
Flowering/Fruiting Period: June-July.
Reproduces by seed. Annual fruit production
appears to be low due to insect and droughtinduced abortion. Mature plants may spread
by rhizomes (although this remains to be
shown). Seed germination experiments by Dr.
Dick Scott have shown that seeds have a
Above: Yermo xanthocephalus by Jane Dorn.
Below: Y. xanthocephalus by Jennifer Whipple.
higher germination rate when given a warm
treatment rather than a cold treatment. This
suggests that seeds may germinate the same
season they are produced.
Distribution: Endemic to the Sweetwater
River Plateau in Fremont County, Wyoming.
Habitat: Yermo xanthocephalus occurs in
sparsely vegetated cushion plant communities
on low slopes, rim margins, colluvial fans,
and bottoms within deflation hollows.
Associated species include Arenaria hookeri,
Astragalus kentrophyta, Cryptantha
caespitosa, Haplopappus nuttallii, Ivesia
gordonii, Phlox muscoides, P. pungens, &
Senecio canus. It is typically absent from
surrounding areas dominated by Wyoming
big sagebrush, bluebunch wheatgrass, and
needle-and-thread. Y. xanthocephalus is
occasionally found in beds of seldom-used
two-tracks. Soils occupied by this species are
dry, shallow, silty-clay entisols derived from
the Miocene-age Split Rock Formation
(Fertig 1994).
Occurrences in Wyoming: Known from a
single occurrence in Wyoming (and globally),
last observed in 2001. Surveys from 19902001 have failed to document additional sites.
Abundance: The population was originally
reported as ca 500 individuals by Dorn
(1991). This did not include all
subpopulations and underestimated
nonflowering plants. Richard Scott of Central
Wyoming College has been conducting
annual population censuses since 1995 and
has documented an increase from 9293 plants
to 13,244 plants in 2000 (Scott 2000).
Trends: Monitoring by Richard Scott (19952001) found the population trends to be
relatively stable and increasing overall.
Protection status: The Cedar Rim site is
managed for multiple use. The area has been
recommended for ACEC status by Fertig
(1995).
Threats: Potential threats include
construction associated with oil and gas
development (including trampling or blasting
by seismic studies), off-road vehicle
trampling, mining, and trampling by
livestock. The plant's small population size
and range makes it extremely vulnerable to
extinction due to chance, natural events or
human-induced disturbances
Above: Habitat of Yermo xanthocephalus at base of
slopes and washes in silty clays. Photo by W. Fertig.
Managed Areas: Occurs on lands managed
by the BLM Lander Field Office.
Fertig, W., C. Refsdal, and J. Whipple. 1994.
Wyoming Rare Plant Field Guide. Wyoming
Rare Plant Technical Committee, Cheyenne
Wyoming.
Heidel, B. 2002. Status report on Desert
Yellowhead (Yermo xanthocephalus) in
Wyoming. Prepared for the Bureau of Land
Management by the Wyoming Natural
Diversity Database, Laramie.
#
Wyoming distribution of Yermo xanthocephalus.
References:
Barkley, T.M. 1999. The segregates of
Senecio, s.l. and Cacalia, s.l., in the flora of
North America north of Mexico. Sida
18:661-672.
Breckenridge, C. 1999. Desert yellowhead
(Yermo xanthocephalus) Conservation
agreement, asessment, and strategy (draft).
USDI Bureau of Land Management and US
Fish and Wildlife Service.
Dorn, R.D. 1991. Yermo xanthocephalus
(Asteraceae: Senecioneae): A new genus and
species from Wyoming. Madrono 38(3): 198201.
Fertig, W. 1995. Status report on Yermo
xanthocephalus in central Wyoming.
Unpublished report prepared for the BLM
Wyoming State Office and Rawlins District
by the Wyoming Natural Diversity Database.
Scott, R.W. 2000. Field studies on Yermo
xanthocephalus Dorn. Report prepared for the
Bureau of Land Management. Department of
Biology, Central Wyoming College,
Riverton, WY.
Scott, R. and B. Hoster. 2000. On the
germination and viability of Yermo
xanthocephalus achenes. Castilleja 19(1): 46.
USDI Fish and Wildlife Service. 1998.
Endangered and Threatened Wildlife and
Plants: Threatened status for the plant Yermo
xanthocephalus. Federal Register 63(245):
70745-70751.
USDI Fish and Wildlife Service. 2002.
Endangered or Threatened species; Listing
the Desert Yellowhead as Threatened. Federal
Register 67(50): 11442-11449.
Author: Walter Fertig and Bonnie Heidel
Updated: 02-03-30