Ambrosia pumila
(Nutt.) A. Gray
San Diego Ragweed
G1Critically ImperiledGlobal Rank
Very highThreat Impact
U.S. Fish & Wildlife Service, https://www.usa.gov/government-works
Identity
Unique IDELEMENT_GLOBAL.2.154697
Element CodePDAST0C0M0
Record TypeSPECIES
ClassificationSpecies
Classification StatusStandard
Name CategoryVascular Plant
Endemicoccurs (regularly, as a native taxon) in multiple nations
KingdomPlantae
PhylumAnthophyta
ClassDicotyledoneae
OrderAsterales
FamilyAsteraceae
GenusAmbrosia
Other Common Names
San Diego Ambrosia (EN)
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 MethodLegacy Rank calculation - Biotics v1
Review Date2020-02-28
Change Date1997-03-14
Edition Date2020-02-28
Edition AuthorsBittman, R.L., rev. D. Gries (1999), rev. L. Oliver and R. Bittman (2020)
Threat ImpactVery high
Range Extent20,000-200,000 square km (about 8000-80,000 square miles)
Number of Occurrences21 - 80
Rank Reasons
Ambrosia pumila is known from sixteen extant populations in Riverside and San Diego Counties, California, and Baja California, Mexico. Twenty-three populations have been extirpated in San Diego County. Only seven United States populations are considered secure and protected. There are many on-going threats to this species including development, physical destruction of plants from land-use and recreation, non-native plants and climate change. Given that this species is known to reproduce clonally, with low viable seed set, there are concerns that the genetic variability is low and hinder the species to adapt to future environmental changes.
Range Extent Comments
This species occurs in the United States and Mexico. In California, it occurs from northwest Riverside County south through western San Diego County, from Lake Hodges to the border, and to southern Baja California, Mexico (R. Bittman, pers. comm., n.d., USFWS, 2010 and Fish and Wildlife Service 1999).
Occurrences Comments
It is known from an estimated 53 documented historical and current populations. In San Diego County, California, of the 48 reported populations, 23 have been extirpated, 11 have been misidentified, leaving 14 extant populations. In Riverside County, California, there are two extant populations, and in Baja California, Mexico, there are three extant populations (Fish and Wildlife Service 1999). In 2010, there were 16 extant occurrences (USFWS 2010).
Threat Impact Comments
This species is highly threatened in California and moderately threatened in Baja California, Mexico. It is impacted by many threats, but the primary threat being habitat destruction from development. The USFWS (2010) lists many other threats including destruction of plants from land-use activities such as discing, mowing, plowing and grading. Other activities that damage plants include trampling by hikers, horses and grazing cattle. Invasive species and climate change are also threats (USFWS 2010). The Baja California populations are threatened by agricultural practices and urban development (U.S. Fish and Wildlife Service 1999). These threats are on-going.
Ecology & Habitat
Diagnostic Characteristics
Ambrosia pumila can be distinguished by its leaves canescently silky-pilose, finely dissected, the ultimate division about 1 mm wide; leaves pinnately lobed in bi- or tripinnatifid (Ferris, 1960).
Habitat
This species occurs in disturbed areas and vernal pools of coastal scrub, grasslands, open floodplains and low valley bottoms below 150 m elevation. It persists where disturbance has been superficial.
Terrestrial Habitats
Shrubland/chaparralGrassland/herbaceous
Palustrine Habitats
TEMPORARY POOL
Other Nations (1)
United StatesN1
| Province | Rank | Native |
|---|---|---|
| California | S1 | Yes |
Threat Assessments
| Threat | Scope | Severity | Timing |
|---|---|---|---|
| 1 - Residential & commercial development | Large (31-70%) | Serious or 31-70% pop. decline | High (continuing) |
| 1.1 - Housing & urban areas | Large (31-70%) | Serious or 31-70% pop. decline | High (continuing) |
| 2 - Agriculture & aquaculture | Pervasive (71-100%) | Serious or 31-70% pop. decline | High (continuing) |
| 2.1 - Annual & perennial non-timber crops | Large (31-70%) | Serious or 31-70% pop. decline | High (continuing) |
| 2.1.4 - Scale unknown/unrecorded | Large (31-70%) | Serious or 31-70% pop. decline | High (continuing) |
| 2.3 - Livestock farming & ranching | Pervasive - large | Serious - slight | High (continuing) |
| 2.3.4 - Scale unknown/unrecorded | Pervasive - large | Serious - slight | High (continuing) |
| 6 - Human intrusions & disturbance | Large (31-70%) | Moderate or 11-30% pop. decline | High (continuing) |
| 6.1 - Recreational activities | Large (31-70%) | Moderate or 11-30% pop. decline | High (continuing) |
| 7 - Natural system modifications | Pervasive (71-100%) | Serious or 31-70% pop. decline | High (continuing) |
| 7.3 - Other ecosystem modifications | Pervasive (71-100%) | Serious or 31-70% pop. decline | High (continuing) |
| 8 - Invasive & other problematic species, genes & diseases | Pervasive (71-100%) | Moderate - slight | High (continuing) |
| 8.1 - Invasive non-native/alien species/diseases | Pervasive (71-100%) | Moderate - slight | High (continuing) |
| 8.1.1 - Unspecified species | Pervasive (71-100%) | Moderate - slight | High (continuing) |
| 11 - Climate change & severe weather | Pervasive (71-100%) | Unknown | High (continuing) |
Plant Characteristics
DurationPERENNIAL
Economic Value (Genus)No
Roadless Areas (7)
California (7)
| Area | Forest | Acres |
|---|---|---|
| Coldwater | Cleveland National Forest | 8,402 |
| Cutca Valley | Cleveland National Forest | 14,530 |
| Ladd | Cleveland National Forest | 5,300 |
| San Mateo Canyon | Cleveland National Forest | 65 |
| Trabuco | Cleveland National Forest | 23,341 |
| Wildhorse | Cleveland National Forest | 1,483 |
| Wildhorse | Cleveland National Forest | 1,483 |
References (9)
- Ferris, R.S. 1960. Illustrated flora of the Pacific states: Washington, Oregon, and California. Vol. IV. Bignoniaceae to Compositae. Stanford Univ. Press, Stanford, CA. 732 pp.
- Flora of North America Editorial Committee (FNA). 2006c. Flora of North America north of Mexico. Vol. 21. Magnoliophyta: Asteridae, part 8: Asteraceae, part 3. Oxford Univ. Press, New York. xxii + 616 pp.
- 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.
- Munz, P.A., with D.D. Keck. 1959. A California flora. Univ. California Press, Berkeley. 1681 pp.
- 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.
- Smith, J.P., and K. Berg. 1988. California native plant society's inventory of rare and endangered vascular plants of California. 4th edition. California Native Plant Society, Sacramento. 168 pp.
- U.S. Fish and Wildlife Service. 2010. <i>Ambrosia pumila </i>(Sand Diego ambrosia) 5-Year Review: summary and evaluation. U.S. Fish and Wildlife Service, Carlsbad Fish and Wildlife Office, Carlsbad, California. Accessed online on 1/7/2020 at: <a href="https://www.fws.gov/carlsbad/SpeciesStatusList/5YR/20100715_5YR_AMPU.pdf">https://www.fws.gov/carlsbad/SpeciesStatusList/5YR/20100715_5YR_AMPU.pdf</a>
- U.S. Fish and Wildlife Service (USFWS). 1999. Endangered and threatened wildlife and plants; 90-day finding for a petition to list the <i>Ambrosia pumila</i> (San Diego Ambrosia) as endangered. Federal Register 64(74):19108-19111.
- Wiggins, I.L. 1980. Flora of Baja California. Stanford Univ. Press, Stanford, California. 1025 pp.