Acanthomintha duttonii
Encyclopedia
Acanthomintha duttonii is a species
of annual plant
endemic to San Mateo County, California
in the Lamiaceae
family. It is commonly called San Mateo Thornmint or Dutton's acanthomintha and is found growing on Serpentine soils near the Crystal Springs Reservoir
in a six mile (10 km) long strip on the east side of Montara Mountain
at elevations of approximately 150 to 300 meters.
on nearby Butano Ridge.
s in the inflorescence have marginal spines, thus the basis of the common name ‘thornmints’. All Acanthomintha have the upper three lobes of its calyx acuminate and the lower two lobes oblong in shape; furthermore, all Acanthomintha corollae are funnel shaped and white with occasional tinting of purple. Each Acanthomintha species has four stamens, with the upper two reduced. Thornmint styles are slender and their fruit is ovoid in shape with a smooth exterior texture.
is five to eight millimeters in length, while the corolla is 12 to 16 millimeters in extent. The white corolla is often tinged lavender in color; the corolla throat is cream colored and its upper lip is hooded, while the longer lower lip is reflexed and three-lobed. The upper lip is more diminutive than the lower, and is entire and shallowly hooded. The flower bracts are broadly ovate in shape with puberulent hairs and shiny. The bracts have seven to nine spines each. The anthers are short and hairy. The style is glabrous. Plants bloom in April into late June, with each flower when fertilized producing four nut-like seeds. Plants are self fertile. A. duttonii upper stamen
s are fertile, while the other species have sterile upper stamans. The presence of these fertile upper stamens is used to separate it as a different species from Acanthomintha obovata, in the past A. duttonii was referred to as subspecies of A. obovata (Acanthomintha obovata ssp. duttonii).
s in grassland communities that are generally species rich for serpentine soils, the area they are growing in on the San Francisco Peninsula
also contains sloping chaparral
. Others species that grow in the same area include Nasella pulchra, Lolium multiflorum, Delphinium hesperium, and Hemizonia congesta var. luzulifolia. The range of this species is sharply limited within a portion of central San Mateo County on the eastern lower slopes of the Santa Cruz Mountains
. Specific plant communities where this species is found are chaparral
as well as foothill or valley
grassland
s. San Mateo Thornmint populations occupy slopes or flatland with deep, heavy clay soil inclusions. The single remaining large population, in Edgewood County Park
, is a relict
of a more extensive colony damaged by off road motor-vehicle use. There is an introduced population at Pulgas Ridge Open Space Preserve
, and native fragments along the lower slopes above Crystal Springs Reservoir
in a six mile (10 km) long fragmented strip that includes the Edgewood colony.
This species is only known to grow on Serpentine soils. Serpentine soils normally provide an inhospitable environment for most plants. Several factors contribute to serpentine soils being inhospitable to plant growth including a low calcium
-magnesium
ratio, lack of essential nutrient
s namely nitrogen
, potassium
, and phosphorus
, and high concentrations of heavy metals. Many species that have adapted to grow on serpentine soils are not adapted to compete with other plants and do not survive well under competition in other soils that tend to have denser plant numbers, in serpentine soils plant densities are lower resulting in less direct competition for resources like light, water etc.
lists San Mateo Thornmint as "rare, threatened, or endangered in California" under List 1B.1, and further classifies this plant as "seriously endangered in California". A state of California endangerment rank of S1.1 has been assigned, implying that there are fewer than six occurrences, fewer than 1000 individuals or fewer than 2000 acres (8 km²). In the case of A. duttonii, the criteria of occurrences and area may both be present. A global rank of G1 (Critically imperilled globally) has been attached to this wildflower.
Significant threats to the limited population of A. duttonii exist due to continuing urbanization of the San Francisco Peninsula
, an inherently fragmented population and off road vehicle use. Two and possibly three colonies of San Mateo Thornmint have been eradicated in the last two decades by off road vehicle use and road maintenance crews.
Species
In biology, a species is one of the basic units of biological classification and a taxonomic rank. A species is often defined as a group of organisms capable of interbreeding and producing fertile offspring. While in many cases this definition is adequate, more precise or differing measures are...
of annual plant
Annual plant
An annual plant is a plant that usually germinates, flowers, and dies in a year or season. True annuals will only live longer than a year if they are prevented from setting seed...
endemic to San Mateo County, California
San Mateo County, California
San Mateo County is a county located in the San Francisco Bay Area of the U.S. state of California. It covers most of the San Francisco Peninsula just south of San Francisco, and north of Santa Clara County. San Francisco International Airport is located at the northern end of the county, and...
in the Lamiaceae
Lamiaceae
The mints, taxonomically known as Lamiaceae or Labiatae, are a family of flowering plants. They have traditionally been considered closely related to Verbenaceae, but in the 1990s, phylogenetic studies suggested that many genera classified in Verbenaceae belong instead in Lamiaceae...
family. It is commonly called San Mateo Thornmint or Dutton's acanthomintha and is found growing on Serpentine soils near the Crystal Springs Reservoir
Crystal Springs Reservoir
Crystal Springs Reservoir is a pair of artificial lakes located in the northern Santa Cruz Mountains of San Mateo County, California situated in the rift valley created by the San Andreas Fault just to the west of the cities of San Mateo and Hillsborough, and I-280...
in a six mile (10 km) long strip on the east side of Montara Mountain
Montara Mountain
Montara Mountain, positioned between the unincorporated community of Montara, California to the southwest and the city of Pacifica, California to the north, forms the northern spur of the Santa Cruz Mountains, a narrow mountain range running the length of the San Francisco Peninsula that separates...
at elevations of approximately 150 to 300 meters.
Distribution
This rare annual species of wildflower has populations that fluctuates yearly with recorded population ranges from 50,000 plants to as few as 5,000 plants and is considered critically endangered due to the species narrow range of growing conditions and the fragmented nature of the populations over the limited habitat and by the encroachment of urban development. The species is named in honor of Harry Arnold Dutton (1873-1957), who, in 1949, located a patch of another rare plant Cupressus abramsianaCupressus abramsiana
Cupressus abramsiana is a cypress taxon of disputed status, placed in either the genus Cupressus or else Callitropsis...
on nearby Butano Ridge.
All Acanthomintha species
All four thornmint species are aromatic annual wildflowers native to the state of California in the USA. The species have square stems that are erect growing. The leaves are petioled with leaf veins conspicuous and the leaf margins are often spiny. The Inflorescences of the Acanthomintha genus are described as "head-like, in terminal clusters" by the genus authority James D. Jokerst. The flowers of this entire genus are like, most mints, two-lipped forming a tube with five sepals and the stamens enclosed with in the zygomorphic petals. The bractBract
In botany, a bract is a modified or specialized leaf, especially one associated with a reproductive structure such as a flower, inflorescence axis, or cone scale. Bracts are often different from foliage leaves. They may be smaller, larger, or of a different color, shape, or texture...
s in the inflorescence have marginal spines, thus the basis of the common name ‘thornmints’. All Acanthomintha have the upper three lobes of its calyx acuminate and the lower two lobes oblong in shape; furthermore, all Acanthomintha corollae are funnel shaped and white with occasional tinting of purple. Each Acanthomintha species has four stamens, with the upper two reduced. Thornmint styles are slender and their fruit is ovoid in shape with a smooth exterior texture.
Acanthomintha duttonii
A. duttonii has a stem which is generally unbranched and less than twenty centimeters in length; the stem may present short hairs or none at all. Leaves of this species are eight to twelve millimeters in length, lanceolate to obovate in shape. The margins of this spiny leaf are occasionally serrate. The terminal inflorescences have bracts of about five to eleven millimeters; moreover, these bracts are ovate and green at the flower, with five or seven marginal spines, each three to seven millimeters. The virtually hairless to sparse short haired calyxSepal
A sepal is a part of the flower of angiosperms . Collectively the sepals form the calyx, which is the outermost whorl of parts that form a flower. Usually green, sepals have the typical function of protecting the petals when the flower is in bud...
is five to eight millimeters in length, while the corolla is 12 to 16 millimeters in extent. The white corolla is often tinged lavender in color; the corolla throat is cream colored and its upper lip is hooded, while the longer lower lip is reflexed and three-lobed. The upper lip is more diminutive than the lower, and is entire and shallowly hooded. The flower bracts are broadly ovate in shape with puberulent hairs and shiny. The bracts have seven to nine spines each. The anthers are short and hairy. The style is glabrous. Plants bloom in April into late June, with each flower when fertilized producing four nut-like seeds. Plants are self fertile. A. duttonii upper stamen
Stamen
The stamen is the pollen producing reproductive organ of a flower...
s are fertile, while the other species have sterile upper stamans. The presence of these fertile upper stamens is used to separate it as a different species from Acanthomintha obovata, in the past A. duttonii was referred to as subspecies of A. obovata (Acanthomintha obovata ssp. duttonii).
Distribution and habitat
This species is normally associated with serpentine soilSerpentine soil
A serpentine soil is derived from ultramafic rocks, in particular serpentinite, a rock formed by the hydration and metamorphic transformation of ultramafic rock from the Earth's mantle....
s in grassland communities that are generally species rich for serpentine soils, the area they are growing in on the San Francisco Peninsula
San Francisco Peninsula
The San Francisco Peninsula is a peninsula in the San Francisco Bay Area that separates the San Francisco Bay from the Pacific Ocean. On its northern tip is the City and County of San Francisco. Its southern base is in Santa Clara County, including the cities of Palo Alto, Los Altos, and Mountain...
also contains sloping chaparral
Chaparral
Chaparral is a shrubland or heathland plant community found primarily in the U.S. state of California and in the northern portion of the Baja California peninsula, Mexico...
. Others species that grow in the same area include Nasella pulchra, Lolium multiflorum, Delphinium hesperium, and Hemizonia congesta var. luzulifolia. The range of this species is sharply limited within a portion of central San Mateo County on the eastern lower slopes of the Santa Cruz Mountains
Santa Cruz Mountains
The Santa Cruz Mountains, part of the Pacific Coast Ranges, are a mountain range in central California, United States. They form a ridge along the San Francisco Peninsula, south of San Francisco, separating the Pacific Ocean from San Francisco Bay and the Santa Clara Valley, and continuing south,...
. Specific plant communities where this species is found are chaparral
Chaparral
Chaparral is a shrubland or heathland plant community found primarily in the U.S. state of California and in the northern portion of the Baja California peninsula, Mexico...
as well as foothill or valley
Valley
In geology, a valley or dale is a depression with predominant extent in one direction. A very deep river valley may be called a canyon or gorge.The terms U-shaped and V-shaped are descriptive terms of geography to characterize the form of valleys...
grassland
Grassland
Grasslands are areas where the vegetation is dominated by grasses and other herbaceous plants . However, sedge and rush families can also be found. Grasslands occur naturally on all continents except Antarctica...
s. San Mateo Thornmint populations occupy slopes or flatland with deep, heavy clay soil inclusions. The single remaining large population, in Edgewood County Park
Edgewood County Park
Edgewood County Park and Natural Preserve is a 467-acre protected area located in San Mateo County, San Francisco, United States, and is best known for its spring wildflower displays...
, is a relict
Relict
A relict is a surviving remnant of a natural phenomenon.* In biology a relict is an organism that at an earlier time was abundant in a large area but now occurs at only one or a few small areas....
of a more extensive colony damaged by off road motor-vehicle use. There is an introduced population at Pulgas Ridge Open Space Preserve
Pulgas Ridge Open Space Preserve
Pulgas Ridge Open Space Preserve is a public recreation area in the Santa Cruz Mountains, San Mateo County in northern California. It is managed by the Midpeninsula Regional Open Space District ....
, and native fragments along the lower slopes above Crystal Springs Reservoir
Crystal Springs Reservoir
Crystal Springs Reservoir is a pair of artificial lakes located in the northern Santa Cruz Mountains of San Mateo County, California situated in the rift valley created by the San Andreas Fault just to the west of the cities of San Mateo and Hillsborough, and I-280...
in a six mile (10 km) long fragmented strip that includes the Edgewood colony.
This species is only known to grow on Serpentine soils. Serpentine soils normally provide an inhospitable environment for most plants. Several factors contribute to serpentine soils being inhospitable to plant growth including a low calcium
Calcium
Calcium is the chemical element with the symbol Ca and atomic number 20. It has an atomic mass of 40.078 amu. Calcium is a soft gray alkaline earth metal, and is the fifth-most-abundant element by mass in the Earth's crust...
-magnesium
Magnesium
Magnesium is a chemical element with the symbol Mg, atomic number 12, and common oxidation number +2. It is an alkaline earth metal and the eighth most abundant element in the Earth's crust and ninth in the known universe as a whole...
ratio, lack of essential nutrient
Nutrient
A nutrient is a chemical that an organism needs to live and grow or a substance used in an organism's metabolism which must be taken in from its environment. They are used to build and repair tissues, regulate body processes and are converted to and used as energy...
s namely nitrogen
Nitrogen
Nitrogen is a chemical element that has the symbol N, atomic number of 7 and atomic mass 14.00674 u. Elemental nitrogen is a colorless, odorless, tasteless, and mostly inert diatomic gas at standard conditions, constituting 78.08% by volume of Earth's atmosphere...
, potassium
Potassium
Potassium is the chemical element with the symbol K and atomic number 19. Elemental potassium is a soft silvery-white alkali metal that oxidizes rapidly in air and is very reactive with water, generating sufficient heat to ignite the hydrogen emitted in the reaction.Potassium and sodium are...
, and phosphorus
Phosphorus
Phosphorus is the chemical element that has the symbol P and atomic number 15. A multivalent nonmetal of the nitrogen group, phosphorus as a mineral is almost always present in its maximally oxidized state, as inorganic phosphate rocks...
, and high concentrations of heavy metals. Many species that have adapted to grow on serpentine soils are not adapted to compete with other plants and do not survive well under competition in other soils that tend to have denser plant numbers, in serpentine soils plant densities are lower resulting in less direct competition for resources like light, water etc.
Conservation
This species became state of California listed as endangered in July 1979 and federally listed as endangered on October 18, 1989. The state of CaliforniaCalifornia
California is a state located on the West Coast of the United States. It is by far the most populous U.S. state, and the third-largest by land area...
lists San Mateo Thornmint as "rare, threatened, or endangered in California" under List 1B.1, and further classifies this plant as "seriously endangered in California". A state of California endangerment rank of S1.1 has been assigned, implying that there are fewer than six occurrences, fewer than 1000 individuals or fewer than 2000 acres (8 km²). In the case of A. duttonii, the criteria of occurrences and area may both be present. A global rank of G1 (Critically imperilled globally) has been attached to this wildflower.
Significant threats to the limited population of A. duttonii exist due to continuing urbanization of the San Francisco Peninsula
San Francisco Peninsula
The San Francisco Peninsula is a peninsula in the San Francisco Bay Area that separates the San Francisco Bay from the Pacific Ocean. On its northern tip is the City and County of San Francisco. Its southern base is in Santa Clara County, including the cities of Palo Alto, Los Altos, and Mountain...
, an inherently fragmented population and off road vehicle use. Two and possibly three colonies of San Mateo Thornmint have been eradicated in the last two decades by off road vehicle use and road maintenance crews.