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Oxytheca watsonii

Torr. & Gray

Watson's Oxytheca

G2Imperiled Found in 3 roadless areas NatureServe Explorer →
G2ImperiledGlobal Rank
HighThreat Impact
Identity
Unique IDELEMENT_GLOBAL.2.131777
Element CodePDPGN0J070
Record TypeSPECIES
ClassificationSpecies
Classification StatusStandard
Name CategoryVascular Plant
Endemicendemic to a single nation
KingdomPlantae
PhylumAnthophyta
ClassDicotyledoneae
OrderPolygonales
FamilyPolygonaceae
GenusOxytheca
Concept Reference
Kartesz, J.T. 1994. A synonymized checklist of the vascular flora of the United States, Canada, and Greenland. 2nd edition. 2 vols. Timber Press, Portland, OR.
Conservation Status
Rank Method Rank calculation - Biotics v2
Review Date2025-03-05
Change Date2025-03-05
Edition Date2025-03-04
Edition AuthorsD. Gries; M. Martinez; R. Bittman (7/98), rev. Johnson, J. (2025)
Threat ImpactHigh
Range Extent20,000-200,000 square km (about 8000-80,000 square miles)
Number of Occurrences21 - 80
Rank Reasons
Oxytheca watsonii is a small, annual herb native to the western Great Basin in Nevada and California, United States. Approximately half of the small, scattered populations are threatened by livestock grazing, off-road vehicle use, and solar energy development.
Range Extent Comments
Oxytheca watsonii is native to the western Great Basin from western and central Nevada to eastern California, United States. Range extent was estimated using herbarium specimens and NatureServe Network occurrence data collected between 1994 and 2025 (RARECAT 2024, GBIF 2025, NatureServe 2025, SEINet 2025, CNDDB 2025).
Occurrences Comments
By applying a 1 km separation distance to herbarium specimens, photo-based observations, and NatureServe Network occurrence data documented between 1994 and 2025, it is estimated that there are 17 occurrences rangewide (RARECAT 2024, GBIF 2025, iNaturalist 2025, NatureServe 2025, SEINet 2025, CNDDB 2025).
Threat Impact Comments
Populations in California occur in protected areas such as Death Valley National Park and Sacatar Trail Wilderness area and face few threats. Populations in Nevada are threatened by livestock and feral horse grazing. While the animals probably do not select for these plants, the associated trampling and weed introduction likely impact them. The flat, sandy habitat is easily impacted by recreational vehicles. The flat, valley-bottom habitat is also valuable for solar energy developments. While no occurrences are currently within a proposed solar development, several Nevada populations are within areas identified as available for solar development or transmission corridors (BLM 2024, BLM 2025). While most of the occurrences in Nevada and Death Valley National Park are close to roads, this likely due to survey bias and not an indication of threats due to road construction.
Ecology & Habitat

Habitat

Joshua tree "woodland", Mohavean desert scrub, and saltbush communities on sandy flats and slopes (Skinner, 1997, FNA 2005). Occurrences in the southern Sierra Nevada mountains are found on decomposing granite in open confer woodland (SEINet 2025).
Terrestrial Habitats
Woodland - MixedDesert
Other Nations (1)
United StatesN2
ProvinceRankNative
NevadaS3Yes
CaliforniaS1Yes
Threat Assessments
ThreatScopeSeverityTiming
2 - Agriculture & aquacultureLarge (31-70%)Moderate or 11-30% pop. declineHigh (continuing)
2.3 - Livestock farming & ranchingLarge (31-70%)Moderate or 11-30% pop. declineHigh (continuing)
3 - Energy production & miningRestricted (11-30%)Serious or 31-70% pop. declineModerate (short-term)
3.3 - Renewable energyRestricted (11-30%)Serious or 31-70% pop. declineModerate (short-term)
4 - Transportation & service corridorsRestricted (11-30%)Moderate or 11-30% pop. declineModerate (short-term)
4.2 - Utility & service linesRestricted (11-30%)Moderate or 11-30% pop. declineModerate (short-term)
6 - Human intrusions & disturbanceLarge (31-70%)Moderate or 11-30% pop. declineHigh (continuing)
6.1 - Recreational activitiesLarge (31-70%)Moderate or 11-30% pop. declineHigh (continuing)

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Plant Characteristics
DurationANNUAL
Economic Value (Genus)No
Roadless Areas (3)
California (2)
AreaForestAcres
Domeland Add.Sequoia National Forest3,046
South SierraInyo National Forest41,853
Nevada (1)
AreaForestAcres
Toquima CaveHumboldt-Toiyabe National Forest43,147
References (15)
  1. Bittman, R. 1998. Lead Botanist, California Natural Diversity Database. Unpublished notes on fifty rare plants of California for purposes of updating Element Global Ranking (EGR) forms. California Natural Heritage Division, Dep. of Fish & Game, Sacramento, California, U.S.A.
  2. Bureau of Land Management (BLM). 2024. Utility-Scale Solar Energy Development Programmatic Environmental Impact Statement. DOI-BLM-HQ-3000-2023-0001-RMP-EIS. https://eplanning.blm.gov/eplanning-ui/project/2022371/510
  3. Bureau of Land Management (BLM). 2025. Greenlink West Transmission Project EIS. DOI-BLM-NV-0000-2022-0004-EIS. https://eplanning.blm.gov/eplanning-ui/project/2017391/510
  4. California Natural Diversity Database (CNDDB). 2025. RareFind Version 5.3.0. California Department of Fish and Game, Sacramento.
  5. Flora of North America Editorial Committee (FNA). 2005. Flora of North America north of Mexico. Vol. 5. Magnoliophyta: Caryophyllidae: Caryophyllales, Polygonales, and Plumbaginales. Oxford Univ. Press, New York. vii + 656 pp.
  6. Global Biodiversity Information Facility (GBIF). 2025. Global Biodiversity Information Facility (GBIF) data portal. Online. Available: https://www.gbif.org/ (accessed 2025).
  7. Hickman, J. C., ed. 1993. The Jepson manual: Higher plants of California. University of California Press, Berkeley, CA. 1400 pp.
  8. iNaturalist. 2025. Online. Available: https://www.inaturalist.org (accessed 2025).
  9. Kartesz, J.T. 1988. A flora of Nevada. Ph.D. dissertation. Univ. of Nevada, Reno. 3 volumes. 1729 pp.
  10. Kartesz, J.T. 1994. A synonymized checklist of the vascular flora of the United States, Canada, and Greenland. 2nd edition. 2 vols. Timber Press, Portland, OR.
  11. Mozingo, H.N., and M. Williams. 1980. The threatened and endangered plants of Nevada. U.S. Fish and Wildlife Service and Bureau of Land Management, Portland, OR. 268 pp.
  12. NatureServe. 2025. NatureServe Network Biodiversity Location Data. NatureServe, Arlington, Virginia.
  13. NatureServe's Rapid Analysis of Rarity and Endangerment Conservation Assessment Tool (RARECAT). 2024. Version: 1.1.1 (released Oct 01, 2024).
  14. Skinner, M.W., and B.M. Pavlik, eds. 1997 (1994). Inventory of rare and endangered vascular plants of California. 1997 Electronic Inventory Update of 1994 5th edition, California Native Plant Society, Special Publication No. 1, Sacramento.
  15. Southwest Environmental Information Network (SEINet). 2025. Collections Databases. Online. Available: https://swbiodiversity.org/seinet/collections/index.php (accessed 2025).