DRAFT
March 2012
PLANTS
Thorne’s Buckwheat (Eriogonum thornei)
Thorne’s Buckwheat
(Eriogonum thornei)
Legal Status
State: Endangered; S1.11
California Rare Plant Rank:
1B.22
Federal: Bureau of Land
Photo courtesy of Hartmut Wisch.
Management Sensitive
Critical Habitat: N/A
Recovery Planning: N/A
Notes: Previously a candidate for federal listing (58 FR 64828–
64845) but was removed from candidacy on February 28, 1996, in a
notice of review (61 FR 7597–7613).
Taxonomy
Thorne’s buckwheat (Eriogonum thornei) was originally described by
Reveal and Henrickson (1975) as Eriogonum ericifolium var. thornei
and was reclassified as Eriogonum thornei in 1998 (Shultz 1998; IPNI
2005). The taxonomic revision was intended to more accurately
reflect phylogenetic relationships based primarily on species
distribution: the two other varieties of E. ericifolium (ericifolium and
pulchrum) are associated with the Colorado Plateau in Arizona, while
Thorne’s buckwheat is associated with the Mojave Desert in California
(Shultz 1998). Thorne’s buckwheat is in the Polygonaceae family
(Jepson Flora Project 2011). It is a small perennial shrub
approximately 0.4 to 1 decimeter (1.6 to 3.9 inches) in diameter. A full
physical description of the species can be found in the Jepson Flora
Project (2011).
1
2
S1: Critically imperiled; X.1: Very threatened.
1B: Rare, threatened, or endangered in California and elsewhere; X.2: Fairly endangered in California.
1
6668
March 2012
DRAFT
March 2012
PLANTS
Thorne’s Buckwheat (Eriogonum thornei)
Distribution
General
There are two occurrences recorded in the California Natural
Diversity Database (CNDDB) (CDFG 2012a). Thorne’s buckwheat is
known from Fourth of July Canyon along a ridge southeast of Cliff
Canyon Spring in the New York Mountains in San Bernardino County
(Reveal and Henrickson 1975; Reveal 1989). The type locality lies
within the Mojave National Preserve and a second occurrence (which
may be a mis-mapping of the type locality) is recorded a tenth of a
mile to the northeast within BLM land (CDFG 2012a; Figure SP-P32).
This species occurs at elevations from 1,800 to 1,830 meters (5,400 to
5,490 feet) (CNPS 2011).
Distribution and Occurrences within the Plan Area
Historical
The type locality was first recorded in 1973 and lies within the Mojave
National Preserve, and is also the only recent occurrence in the
CNDDB, as discussed below. A second occurrence that dates from
1979 (and which may be a mis-mapping of the type locality) is
recorded a tenth of a mile to the east within BLM land (CDFG 2012a;
Figure SP-P32). Figure SP-P32 shows the type locality as a recent
occurrence.
Recent
The type locality was last seen in 2008 and the record last updated in
2009 (CDFG 2012a). The second occurrence has not been seen since
first reported in 1979 and may be a mis-mapping of the type locality.
As reported above, the type locality occurs within the Mojave National
Preserve and the second occurrence lies within BLM property (CDFG
2012a; Figure SP-P32).
2
6668
March 2012
DRAFT
March 2012
PLANTS
Thorne’s Buckwheat (Eriogonum thornei)
Natural History
Habitat Requirements
Thorne’s buckwheat grows in pinyon and juniper woodland
communities on gravelly substrates (see Table 1; Reveal and
Henrickson 1975; CNPS 2011). The type locality occurs on a
northwest–southeast trending ridgeline. The pinyon and juniper
woodland at the type locality included Utah juniper (Juniperus
osteosperma), pinyon pine (Pinus monophylla), banana yucca (Yucca
baccata), prickly pear (Opuntia spp.) and other shrubs, as well as an
understory of Wright’s buckwheat (Eriogonum wrightii var. wrightii),
Nevada onion (Allium nevadensis var. cristatum), blue grama
(Bouteloua gracilis), rough menodora (Menodora scabra), fineleaf
hymenopappus (Hymenopappus filifolius var. eriopodus), and
viviparous foxtail cactus (Coryphantha vivpara var. rosea) (Reveal and
Henrickson 1975). The soils are sandy loam on quartz monzonite and
are high in copper (300 ppm) (CDFG 2012a; Reveal and Henrickson
1975). The second occurrence (which may be a mis-mapping of the
type locality) is simply listed as occurring along a dirt road near mine
shafts (CDFG 2012a).
Table 1. Habitat Associations for Thorne’s Buckwheat
Land Cover
Type
Pinyon and
juniper
woodland
Habitat
Designation
Primary
Habitat Parameters
Gravelly substrate (high
copper concentrations may
be important (300 ppm));
1,800–1,830 meters (5,400–
5,490 feet)
Supporting
Information
CNPS 2011; CDFG
2012a; Reveal
and Henrickson
1975
Reproduction
Thorne’s buckwheat is a perennial shrub that blooms from July to
August (CNPS 2011; Jepson Flora Project 2011; Reveal 1989). There is
no information available regarding pollinators, seed germination, seed
dispersal, or seedling establishment.
3
6668
March 2012
DRAFT
March 2012
PLANTS
Thorne’s Buckwheat (Eriogonum thornei)
Ecological Relationships
As described in Habitat Requirements, Thorne’s buckwheat is associated
with pinyon and juniper woodland communities on gravelly substrates
(CNPS 2011). This species has a very limited geographic distribution and
little is known of its life history and ecological relationships. Information
regarding pollination, seed germination, dispersal, or seedling
establishment has not been reported for this species.
Population Status and Trends
Global: G1, Critically Imperiled (CDFG 2012b)
State: S1.1, Critically Imperiled (CDFG 2012b)
Thorne’s buckwheat is known from two occurrences in Fourth of July
Canyon. Abundance at the type locality varies from locally abundant
in 1973, to more than100 plants observed in 1981, to “very localized”
in 1983, to 1,500 plants observed in 2005, to an unknown number of
plants in 2008. There is no abundance information for the second
occurrence (which may have been a mis-mapping of the type locality)
(CDFG 2012a). The plant seems to be persistent at the type locality
although factors affecting abundance have not been identified.
Threats and Environmental Stressors
Information regarding threats and environmental stressors has not been
reported for this species. This species is tolerant of high (300 ppm)
copper levels in the soil (CDFG 2012a; Reveal and Henrickson 1975).
Conservation and Management Activities
The type locality occurs within the Mojave National Preserve and the
second occurrence (likely a mis-mapping of the type locality) occurs
on BLM land (CDFG 2012a). There is no information on the
management of Thorne’s buckwheat by the National Park Service or
the BLM; however, the occurrences are presumably afforded some
protection from development based on land ownership.
4
6668
March 2012
DRAFT
March 2012
PLANTS
Thorne’s Buckwheat (Eriogonum thornei)
Data Characterization
The general distribution of Thorne’s buckwheat is well known based
on its very limited geographic distribution (Fourth of July Canyon).
Little is known regarding the species’ pollination, seed germination,
seed dispersal, and recruitment, but the population appears to be
stable or increasing (CDFG 2012a).
Management and Monitoring Considerations
Protection should focus on the two currently known occurrences in
Fourth of July Canyon, one of which occurs in the Mojave National
Preserve and one of which occurs on BLM land (CDFG 2012a).
Additional surveys to confirm the suspected second occurrence, as
well as to identify additional occurrences in the area, would be useful.
Predicted Species Distribution in Plan Area
There are 480 acres of modeled suitable habitat for Thorne’s
buckwheat in the Plan Area. Thorne’s buckwheat has a well-known
distribution and is a narrow endemic species. Therefore, no suitable
expert-based habitat model was developed. Instead, the actual
occurrence data was used to circumscribe its range. Appendix C
includes a figure showing the species’ range in the Plan Area.
Literature Cited
CDFG (California Department of Fish and Game). 2012a. “Eriogonum
thornei.” Element Occurrence Query. California Natural
Diversity Database (CNDDB). RareFind, Version 4.0
(Commercial Subscription). Sacramento, California: CDFG,
Biogeographic Data Branch. Accessed February 2012.
http://www.dfg.ca.gov/biogeodata/cnddb/mapsanddata.asp.
CDFG. 2012b. Special Vascular Plants, Bryophytes, and Lichens List.
California Natural Diversity Database (CNDDB). January 2012.
Accessed March 2012. http://www.dfg.ca.gov/biogeodata/
cnddb/plants_and_animals.asp.
5
6668
March 2012
DRAFT
March 2012
PLANTS
Thorne’s Buckwheat (Eriogonum thornei)
CNPS (California Native Plant Society). 2011. “Eriogonum thornei.”
Inventory of Rare and Endangered Plants (online edition, v801a). Sacramento, California: California Native Plant Society.
Accessed May 2011. http://www.cnps.org/inventory.
IPNI (International Plant Names Index). 2005. “Plant Name Details:
Eriogonum thornei.” Accessed May 2011.
http://www.ipni.org/ipni/idPlantNameSearch.do;jsessionid=7
89C6A9CE58E82A4A5CDD58F55FEA200?id=10023961&back_page=%2Fipni%2FeditSimplePlantNameSearch.do%3
Bjsessionid%3D789C6A9CE58E82A4A5CDD58F55FEA200%3
Ffind_wholeName%3Deriogonum%2Bthornei%26output_for
mat%3Dnormal.
Jepson Flora Project. 2011. “Eriogonum thornei.” The Jepson Online
Interchange: California Floristics. Berkeley, California:
University of California. Accessed May 2011.
http://ucjeps.berkeley.edu/interchange.html.
Reveal, J.L. and J. Henrickson. 1975. “A New Variety of Eriogonum
Ericifolium (Polygonaceae).” Madroño 23(4):205–209.
Reveal, J.L. 1989. “The Eriogonoid Flora of California (Polygonaceae:
Eriogonoideae).” Phytologia 66(4):295–414. Accessed June 6,
2011. http://www.biodiversitylibrary.org/item/47411.
Schultz, L.M. 1998. “A New Species of Eriogonum (Polygonaceae:
Eriogonoideae) from Utah and Nevada.” Harvard Papers in
Botany 3(1):49–52.
6
6668
March 2012