CPC Plant Profile: San Mateo Thornmint
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Plant Profile

San Mateo Thornmint (Acanthomintha duttonii)

This annual herb (with purple-tinged white flowers) can grow to 20 cm tall. Photo Credit: Holly Forbes
Description
  • Global Rank: G1 - Critically Imperiled
  • Legal Status: Federally Endangered
  • Family: Lamiaceae
  • State: CA
  • Nature Serve ID: 135577
  • Date Inducted in National Collection: 08/30/1988

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.

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Updates
  • 09/01/2020
  • Orthodox Seed Banking

Based on an September 2020 extract of the California Plant Rescue Database, University of California Botanical Garden holds 21 accessions of Acanthomintha duttonii in orthodox seed collection. There are as many as 65530 seeds of this species in their collection - although some may have been used for curation testing or sent to back up.

  • 08/05/2020
  • Seed Collection

Based on an August 2020 extract of the California Plant Rescue Database, University of California Botanical Garden has collected 21 seed accessions of Acanthomintha duttonii from 2 plant occurrences listed in the California Natural Diversity Database. These collections together emcompass an unknown number of maternal plants

  • 08/04/2020
  • Orthodox Seed Banking

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.

  • 08/04/2020
  • Seed Collection

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.

  • 08/04/2020
  • Demographic Research

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).

  • 08/04/2020
  • Reintroduction

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).

Nature Serve Biotics
  • 05/02/2017

Only known from a narrow, 10 km stretch in San Mateo County in the San Francisco Bay area of California. Only 2 small populations are known extant. Historically, the species was found scattered infrequently throughout this area, but most populations are believed to have been destroyed by urban and associated highway development. The 2 small remaining populations are located in a county park and adjacent to the park on land managed by the San Francisco Water Department. However, they remain threatened by urban development, vehicles and vandalism.

Holly Forbes
  • 01/01/2010

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).

Holly Forbes
  • 01/01/2010

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.

Holly Forbes
  • 01/01/2010

The county park land is managed by San Mateo County. Nearby fencing helps restrict unauthorized vehicular access.

Holly Forbes
  • 01/01/2010

Studies of nutlet mortality and germination in the seed bank.

Holly Forbes
  • 01/01/2010

Additional collection of seeds to achieve genetic diversity representation in storage (planned for summer 2002).

Holly Forbes
  • 01/01/2010

Small areal extent Development Vandalism Potential change in local environmental conditions from nearby development disturbance by hikers and mountain bikers.

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Photos
Nomenclature
Taxon Acanthomintha duttonii
Authority (Abrams) Jokerst
Family Lamiaceae
CPC Number 20
ITIS 506815
USDA ACDU2
Common Names Dutton's acanthomintha | San Mateo thornmint | San Mateo thorn-mint
Associated Scientific Names Acanthomintha duttonii | Acanthomintha obovata ssp. duttonii
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 t
State Rank
State State Rank
California S1
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).

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).

Pollinators
Common Name Name in Text Association Type Source InteractionID
Bees
Medium to large size bees Confirmed Pollinator Link
Reintroduction
Lead Institution State Reintroduction Type Year of First Outplanting

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