 |
Conserving and restoring
America's native plants |
|
CPC National Collection Plant Profile
|
|
|
Acanthomintha duttonii
| Family: |
Lamiaceae (Mint Family) |
| Common Names: |
Dutton's acanthomintha, San Mateo thornmint |
| Taxon Synonym: |
Acanthomintha obovata ssp. duttonii |
| Author: |
(Abrams) Jokerst |
| Growth
Habit: |
Annual |
| CPC
Number: |
20 |
|
| |
| Primary
custodian for this plant in the CPC National Collection of Endangered
Plants is: |
| |
| Holly Forbes contributed to this Plant Profile. |
Acanthomintha duttonii
|
San Mateo thornmint is found only in serpentine grassland in a small area south of San Francisco, in San Mateo County, California. This annual herb grows erect up to 20 cm. tall; its leaves are 8-12 mm. long, usually with toothed margins. Bracts in the inflorescence have marginal spines and the flowers are white, sometimes tinged with purple. This species is known from only one naturally occurring, fragmented population. The larger fragment occurs on county park land; the smaller fragment, with fewer than 50 plants, is on adjacent land owned by the San Francisco Water Department. Historically, the species was scattered infrequently throughout this area, but most populations (three known) were destroyed by urban and associated highway development.
| Distribution
& Occurrence |
|
State Range
Habitat
| |
This species grows on open substrate on mesic grassland slopes in soils derived from serpentine rock at elevations below 300 m. It grows in a species-rich forb association, including Nasella pulchra, Lolium multiflorum, Delphinium hesperium, and Hemizonia congesta var. luzulifolia (Pavlik and Espeland 1998). |
Distribution
| |
San Mateo thornmint is known only from one fragmented population in San Mateo County, California. It was never collected beyond a narrow, 6-mile long strip from Lower Crystal Springs Reservoir south to Woodside (Jokerst 1991). |
Number Left
| |
The numbers of this annual herb vary by year, from over 53,000 in 1994 to a low of 5,289 in 1997 (Pavlik and Espeland 1998). |
State/Area
Protection
| |
State/Area |
Rank |
Status |
Date |
|
| |
California |
S1.1 |
1 |
|
|
| Conservation,
Ecology & Research |
|
Ecological
Relationships
| |
The species is primarily self-pollinating (Steeck 1995). Each flower can produce up to 4 nutlets. Nutlets from the seed bank can produce plants after 8 years of quiescence during periods of extraordinary annual rainfall (Pavlik and Espeland 1998). |
Threats
| |
• Small areal extent
• Development
• Vandalism
• Potential change in local environmental conditions from nearby development disturbance by hikers and mountain bikers. |
Current Research Summary
| |
An in-depth demographic study and reintroduction attempt was performed from 1990-1997. The natural population significantly and progressively increased in abundance and density between 1990 and 1994, then began a decline that lasted through 1997. In general, high density and high yield (reproductive plants produced from previous year's nutlet production) were associated with average or below-average years of precipitation while low densities and yield were associated with above-average rainfall years. During the entire study period, survivorship to reproduction remained fairly high and consistent, indicating that population trends were due to variations in nutlet production and the influence of cryptic factors that operate in the seed bank. The experimental population differed in several critical respects from the natural population, including low germination, low and variable survivorship, low nutlet production and perhaps high nutlet mortality. These features reduced the potential for self-sustained growth in the experimental population, which is likely to be extirpated within the next few years. This failure to produce a self-sustaining population of Acanthomintha duttonii emphasizes the urgent need for in situ preservation of self-sustaining natural populations of serpentinite species. (Pavlik and Espeland 1998).
Seeds were put into long-term storage at the National Seed Storage Laboratory in 1988 and another collection will be made in 2002 in collaboration with the U.S. Fish & Wildlife Service. |
Current Management Summary
| |
• The county park land is managed by San Mateo County.
• Nearby fencing helps restrict unauthorized vehicular access. |
Research Management Needs
| |
Studies of nutlet mortality and germination in the seed bank. |
Ex Situ Needs
| |
Additional collection of seeds to achieve genetic diversity representation in storage (planned for summer 2002). |
|
| Books (Single Authors)
|
| |
| Thomas, J.H. 1961. Flora of the Santa Cruz Mountains of California. Stanford, California: Stanford University Press. |
| |
| Books (Sections)
|
| |
| Pavlik, B.M. 1994. Demographic monitoring and the recovery of endangered plants. In: Bowles, M.L.; Whelan, C., editors. Recovery and Restoration of Endangered Species. Cambridge University Press. Cambridge. p 322-350. |
| |
| Electronic Sources
|
| |
| CalPhotos. (2002). CalPhotos: Berkely Digital Library Project. University of California, Berkeley. http://elib.cs.berkeley.edu/photos/. Accessed: 2002. |
| |
| USFWS. (2002). Some Threatened & Endangered Plants Found Mainly in California. Sacramento Fish and Wildlife Office, U.S. Fish and Wildlife Service. http://sacramento.fws.gov/es/plant_spp_accts/acctplant.htm. Accessed: 2002. |
| |
| Journal Articles
|
| |
| Jokerst, J.D. 1991. A revision of Acanthomintha obovata (Lamiaceae) and a key to the taxa of Acanthomintha. Madroño. 38: 278-286. |
| |
| Pavlik, B.M.; Espeland, E.K. 1998. Demography of natural and reintroduced populations of Acanthomintha duttonii, an endangered serpentinite annual in Northern California. Madroño. 45: 31-39. |
| |
| USFWS. 1976. Proposed Endangered Status for 1700 U.S. Plants. Federal Register. 41: 24523-24572. |
| |
| USFWS. 1985. Determination of endangered status for Acanthominta obovata ssp. duttonii (San Mateo thornmint). Federal Register. 50, 181: 37858-37863. |
| |
| Reports
|
| |
| USFWS. 1998. Recovery Plan for Serpentine Soil Species of the San Francisco Bay Area. Portland, Oregon: U.S. Fish and Wildlife Service. p.330 + appendices. |
| |
| Theses
|
| |
| Steeck, D.M. 1995. Reproductive biology of a rare California annual, Acanthomintha duttonii, and its congener, Acanthomintha obovata ssp. cordata. [MasterÆs thesis]: University of California. Davis, CA. |
| |
|
