Camissonia benitensis
Encyclopedia
Camissonia benitensis is a species of evening primrose
known by the common name San Benito evening primrose (oddly, it blooms only in the early morning). It is endemic to California
, where its range includes far southern San Benito County
, far western Fresno County
, and far eastern Monterey County
. The species is a strict serpentine
endemic, meaning that it is always found growing on serpentine soils. Serpentine is an ultramafic rock. It weathers to produce soils with characteristically low levels of nutrients like nitrogen
, phosphorus
, potassium
, and calcium
, and high levels of magnesium
and heavy metals including nickel
and chromium
. A major, consistent chemical feature of serpentine soil is a bioavailable calcium:magnesium ratio much less than 1. Most nonserpentine soils have a ratio far greater than 1 (more calcium and much less magnesium). The extreme chemical characteristics of serpentine soils give rise to uniquely-adapted and rare serpentine endemic plant species such as San Benito evening primrose.
on the New Idria serpentine mass (BLM Clear Creek Management Area) and scientifically described in 1969. The plant's specific epithet, "benitensis", commemorates its discovery in San Benito County. It is a diminutive annual herb that rarely grows larger than 10 centimeters in field conditions, but can become multi-branched and exceed 30 centimeters in diameter within a horticultural
setting. Its reddish stems bear plentiful linear leaves less than 1 centimeter long and minutely toothed along the edges. Plants bear four-petaled yellow flowers approximately 6 millimeters in diameter. Flowering occurs in April and May, opening in the morning and closing in early afternoon. The species is fully self-pollinating. The fruit is a cylindrical capsule up to 4 centimeters in length. The fruits remain largely closed at maturity and spring open upon wetting with the first fall rains, dispersing seeds. Seeds are tiny (1 millimeter long, 0.5 millimeter wide) and black to brown in color. The seeds have a smooth seed coat and weigh approximately 0.1 milligram each. Long-distance dispersal
likely occurs as seeds in mud stuck to animals or vehicles. Seeds germinate
with the first rains in fall or winter.
Camissonia benitensis bears a close resemblance to Camissonia contorta
. The two species are virtually indistinguishable with the naked eye when plants are small (under 6 centimeters), as is common in their native habitat, where they occur together. Camissonia strigulosa
also grows in this range but is distinguishable by its smaller flowers and prostrate habit. They dichotomous keys in The Jepson Manual
are not detailed enough to make certain positive identifications. One key characteristic that can help distinguish the three species is the morphology
of the trichome
s on the distal inflorescence
s. C. contorta has trichomes that look like transparent glassy rods. C. strigulosa has white linear or lance-shaped blades. C. benitensis has both kinds of trichomes. This characteristic will be included in the forthcoming edition of the Jepson Manual.
A Camissonia which resembles either C. contorta or C. benitensis growing on serpentine soil in upland geologic transition zone habitat or serpentine stream terrace habitat within serpentine masses is virtually always C. benitensis. A Camissonia resembling either of the two species on serpentine stream terraces outside of serpentine masses or mixed alluvium stream terraces could be either C. contorta or C. benitensis.
, it was long believed that its only habitat type consisted of serpentine alluvial stream terraces adjacent to perennial streams and rivers, a very rare type of habitat. Until 2010 few populations of the species had been found in any other habitat. In 2010 numerous additional populations were discovered on other land forms including ancient serpentine alluvium deposits (upland hills), serpentine landslides originating from tectonic masses (upland), and serpentine soils on the periphery of large tectonic serpentine (ultramafic) masses (upland). These recently discovered habitat types are collectively called the "geologic transition zone." This habitat type is now know to constitute the majority of the habitat area and contains most of the known populations of the species. Populations found near Priest Valley in 2010 extended the previously known range 15 kilometers to the southeast.
Common features of the stream terrace are friable serpentine soils that are stable, not eroding
, and not prone to frost heave. There is usually little or no clay
. The plant communities in the area include chaparral
and woodland with gaps in between where there are microclimate
s. San Benito evening primrose occurs in these gaps. Typical woody vegetation in the area includes Quercus douglasii (blue oak), Juniperus californica (California juniper), Quercus berberidifolia (scrub oak), Quercus durata
(leather oak), Arctostaphylos glauca
(bigberry manzanita) and Ceanothus cuneatus
(buckbrush). Gaps between the woody vegetation have sparse herbaceous plant cover. San Benito evening primrose is generally a poor competitor with other plant species, both native and exotic. Dense woody vegetation (closed shrub gaps) appears to be detrimental to San Benito evening primrose due to shading effects. Some areas of geologic transition zone habitat have been partially invaded by invasive annual grasses such as Bromus madritensis
. These infestations are usually sparse due to the extreme physical and chemical characteristics of the serpentine soils and the low level of tolerance of Bromus madritensis to those soil characteristics. Wildfire
generally has a positive effect on San Benito evening primrose by removing native and invasive vegetation. Prescribed fire is utilized by the Bureau of Land Management to control Centaurea solstitialis which once threatened to invade stream terrace habitat occupied by San Benito evening primrose near the confluence of Clear Creek and San Benito River. Some areas of geologic transition zone habitat on private land are grazed by cattle which like wildfire, is beneficial to San Benito evening primrose by removing competing vegetation, particularly invasive annual grasses.
The current estimated range for San Benito evening primrose is as follows:
with one cycle equal to 2 to 3 years. Total plant numbers for the species can fluctuate from a low of a few hundred plants to tens of thousands of plants during a cycle. The reason for the cycling is unknown but it may be related to predation
by some type of insect
that has a similar cycle. There is no obvious correlation with climate or human factors. Despite the cycling, the overall population remains stable and is slightly increasing.
San Benito evening primrose is well-buffered from extinction by enormous soil seed bank
100 - 1000 times that of the number of plants seen with a population in any given year. Seed in the soil seed bank has been documented to be viable for at least 20 years and likely is to be viable for much longer.
(mercury ore) within the New Idria serpentine mass (BLM Clear Creek Management Area). Numerous European prospectors and cattle ranchers settled throughout the area thereafter. Historic impacts to San Benito evening primrose have included logging
and mining (gravel, magnesite
, chromite
, cinnabar, and chrysotile asbestos). The relatively level stream terraces were historically favored by settlers for home sites and to stage industrial activities. A proposed mineral withdrawal for the New Idria serpentine mass will greatly limit any future mining in the area.
In more recent decades, the BLM Clear Creek Management Area became a popular motorized off-road vehicle
(ORV) recreation area. San Benito evening primrose was federally listed as Threatened in 1985. The primary threat cited by the Fish and Wildlife Service
was off-road vehicle
impacts to habitat. At the time, only nine populations of the species were known with most occurring on serpentine alluvial stream terraces within one of the highest ORV use areas at Clear Creek Manageemnt Area, Clear Creek Canyon. Nearly all of the stream terrace habitat in Clear Creek Canyon has since been fenced to exclude human impacts. A formal route designation in 2005 has further reduced ORV impacts.
The Clear Creek Management Area has been under a temporary Emergency Closure since May 1, 2008 when the Environmental Protection Agency reported that natural occurrences of chrysotile asbestos in the soil was above safe limits for people. As of February 2011, BLM lands within the area are still closed. The unmaintained public county road system through the area remains open.
Onagraceae
Onagraceae, also known as the Willowherb family or Evening Primrose family, are a family of flowering plants. The family includes about 640-650 species of herbs, shrubs, and trees in 20-24 genera...
known by the common name San Benito evening primrose (oddly, it blooms only in the early morning). It is endemic to California
California
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...
, where its range includes far southern San Benito County
San Benito County, California
San Benito County is a county located in the Coast Range Mountains of the U.S. state of California, south of San Jose. As of 2010 the population was 55,269. The county seat is Hollister, which includes nearly two-thirds of the county's population. El Camino Real passes through the county and...
, far western Fresno County
Fresno County, California
Fresno County is a county located in the Central Valley of the U.S. state of California, south of Stockton and north of Bakersfield. As of the 2010 census, it is the tenth most populous county in California with a population of 930,450, and the sixth largest in size with an area of . The county...
, and far eastern Monterey County
Monterey County, California
Monterey County is a county located on the Pacific coast of the U.S. state of California, its northwestern section forming the southern half of Monterey Bay. The northern half of the bay is in Santa Cruz County. As of 2010, the population was 415,057. The county seat and largest city is Salinas...
. The species is a strict serpentine
Serpentinite
Serpentinite is a rock composed of one or more serpentine group minerals. Minerals in this group are formed by serpentinization, a hydration and metamorphic transformation of ultramafic rock from the Earth's mantle...
endemic, meaning that it is always found growing on serpentine soils. Serpentine is an ultramafic rock. It weathers to produce soils with characteristically low levels of nutrients like 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...
, 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...
, 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 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...
, and high levels of 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...
and heavy metals including nickel
Nickel
Nickel is a chemical element with the chemical symbol Ni and atomic number 28. It is a silvery-white lustrous metal with a slight golden tinge. Nickel belongs to the transition metals and is hard and ductile...
and chromium
Chromium
Chromium is a chemical element which has the symbol Cr and atomic number 24. It is the first element in Group 6. It is a steely-gray, lustrous, hard metal that takes a high polish and has a high melting point. It is also odorless, tasteless, and malleable...
. A major, consistent chemical feature of serpentine soil is a bioavailable calcium:magnesium ratio much less than 1. Most nonserpentine soils have a ratio far greater than 1 (more calcium and much less magnesium). The extreme chemical characteristics of serpentine soils give rise to uniquely-adapted and rare serpentine endemic plant species such as San Benito evening primrose.
Description
The species was discovered by Peter H. RavenPeter H. Raven
Peter Hamilton Raven is a botanist and environmentalist, notable as the longtime director, now President Emeritus, of the Missouri Botanical Garden.-Early life:...
on the New Idria serpentine mass (BLM Clear Creek Management Area) and scientifically described in 1969. The plant's specific epithet, "benitensis", commemorates its discovery in San Benito County. It is a diminutive annual herb that rarely grows larger than 10 centimeters in field conditions, but can become multi-branched and exceed 30 centimeters in diameter within a horticultural
Horticulture
Horticulture is the industry and science of plant cultivation including the process of preparing soil for the planting of seeds, tubers, or cuttings. Horticulturists work and conduct research in the disciplines of plant propagation and cultivation, crop production, plant breeding and genetic...
setting. Its reddish stems bear plentiful linear leaves less than 1 centimeter long and minutely toothed along the edges. Plants bear four-petaled yellow flowers approximately 6 millimeters in diameter. Flowering occurs in April and May, opening in the morning and closing in early afternoon. The species is fully self-pollinating. The fruit is a cylindrical capsule up to 4 centimeters in length. The fruits remain largely closed at maturity and spring open upon wetting with the first fall rains, dispersing seeds. Seeds are tiny (1 millimeter long, 0.5 millimeter wide) and black to brown in color. The seeds have a smooth seed coat and weigh approximately 0.1 milligram each. Long-distance dispersal
Biological dispersal
Biological dispersal refers to species movement away from an existing population or away from the parent organism. Through simply moving from one habitat patch to another, the dispersal of an individual has consequences not only for individual fitness, but also for population dynamics, population...
likely occurs as seeds in mud stuck to animals or vehicles. Seeds germinate
Germination
Germination is the process in which a plant or fungus emerges from a seed or spore, respectively, and begins growth. The most common example of germination is the sprouting of a seedling from a seed of an angiosperm or gymnosperm. However the growth of a sporeling from a spore, for example the...
with the first rains in fall or winter.
Camissonia benitensis bears a close resemblance to Camissonia contorta
Camissonia contorta
Camissonia contorta is a species of evening primrose known by the common name plains evening primrose. It is native to western North America from British Columbia to California to Idaho, where it grows in many habitat types. It is an annual herb producing a slender, bending to curling red or green...
. The two species are virtually indistinguishable with the naked eye when plants are small (under 6 centimeters), as is common in their native habitat, where they occur together. Camissonia strigulosa
Camissonia strigulosa
Camissonia strigulosa is a species of flowering plant in the evening primrose family known by the common name sandysoil suncup. It is native to California and Baja California, where it grows in sandy areas, such as beaches and desert. This is an annual herb with a tough, slender, hairy stem which...
also grows in this range but is distinguishable by its smaller flowers and prostrate habit. They dichotomous keys in The Jepson Manual
The Jepson Manual
The Jepson Manual, Higher Plants of California is a collection of identification keys to help biologists identify the vascular plants within the state of California...
are not detailed enough to make certain positive identifications. One key characteristic that can help distinguish the three species is the morphology
Morphology (biology)
In biology, morphology is a branch of bioscience dealing with the study of the form and structure of organisms and their specific structural features....
of the trichome
Trichome
Trichomes are fine outgrowths or appendages on plants and certain protists. These are of diverse structure and function. Examples are hairs, glandular hairs, scales, and papillae.- Algal trichomes :...
s on the distal inflorescence
Inflorescence
An inflorescence is a group or cluster of flowers arranged on a stem that is composed of a main branch or a complicated arrangement of branches. Strictly, it is the part of the shoot of seed plants where flowers are formed and which is accordingly modified...
s. C. contorta has trichomes that look like transparent glassy rods. C. strigulosa has white linear or lance-shaped blades. C. benitensis has both kinds of trichomes. This characteristic will be included in the forthcoming edition of the Jepson Manual.
A Camissonia which resembles either C. contorta or C. benitensis growing on serpentine soil in upland geologic transition zone habitat or serpentine stream terrace habitat within serpentine masses is virtually always C. benitensis. A Camissonia resembling either of the two species on serpentine stream terraces outside of serpentine masses or mixed alluvium stream terraces could be either C. contorta or C. benitensis.
Range and Habitat
Based upon its original discovery on a serpentine alluvial stream terraceStream terrace
Fluvial terraces are elongated terraces that flank the sides of floodplains and fluvial valleys all over the world. They consist of a relatively level strip of land, called a “tread,” separated from either an adjacent floodplain, other fluvial terraces, or uplands by distinctly steeper strips of...
, it was long believed that its only habitat type consisted of serpentine alluvial stream terraces adjacent to perennial streams and rivers, a very rare type of habitat. Until 2010 few populations of the species had been found in any other habitat. In 2010 numerous additional populations were discovered on other land forms including ancient serpentine alluvium deposits (upland hills), serpentine landslides originating from tectonic masses (upland), and serpentine soils on the periphery of large tectonic serpentine (ultramafic) masses (upland). These recently discovered habitat types are collectively called the "geologic transition zone." This habitat type is now know to constitute the majority of the habitat area and contains most of the known populations of the species. Populations found near Priest Valley in 2010 extended the previously known range 15 kilometers to the southeast.
Common features of the stream terrace are friable serpentine soils that are stable, not eroding
Erosion
Erosion is when materials are removed from the surface and changed into something else. It only works by hydraulic actions and transport of solids in the natural environment, and leads to the deposition of these materials elsewhere...
, and not prone to frost heave. There is usually little or no clay
Clay
Clay is a general term including many combinations of one or more clay minerals with traces of metal oxides and organic matter. Geologic clay deposits are mostly composed of phyllosilicate minerals containing variable amounts of water trapped in the mineral structure.- Formation :Clay minerals...
. The plant communities in the area include 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...
and woodland with gaps in between where there are microclimate
Microclimate
A microclimate is a local atmospheric zone where the climate differs from the surrounding area. The term may refer to areas as small as a few square feet or as large as many square miles...
s. San Benito evening primrose occurs in these gaps. Typical woody vegetation in the area includes Quercus douglasii (blue oak), Juniperus californica (California juniper), Quercus berberidifolia (scrub oak), Quercus durata
Quercus durata
Quercus durata is an oak endemic to California.Quercus durata var. durata is a strict serpentine endemic that occurs in the Coast Range and northern Sierra Nevadas. It is often a component of serpentine chaparral...
(leather oak), Arctostaphylos glauca
Arctostaphylos glauca
Arctostaphylos glauca is a species of manzanita known by the common name bigberry manzanita. It is native to California and Baja California, where it grows in the chaparral and woodland of coastal and inland hills.-Description:...
(bigberry manzanita) and Ceanothus cuneatus
Ceanothus cuneatus
Ceanothus cuneatus is a species of flowering shrub known by the common names Buckbrush and wedgeleaf ceanothus.-Distribution:...
(buckbrush). Gaps between the woody vegetation have sparse herbaceous plant cover. San Benito evening primrose is generally a poor competitor with other plant species, both native and exotic. Dense woody vegetation (closed shrub gaps) appears to be detrimental to San Benito evening primrose due to shading effects. Some areas of geologic transition zone habitat have been partially invaded by invasive annual grasses such as Bromus madritensis
Bromus madritensis
Bromus madritensis is a species of brome grass known by the common name compact brome.It is native to Europe but it has been widely introduced elsewhere, such as North America, where it is found in many areas. It is now known nearly worldwide...
. These infestations are usually sparse due to the extreme physical and chemical characteristics of the serpentine soils and the low level of tolerance of Bromus madritensis to those soil characteristics. Wildfire
Wildfire
A wildfire is any uncontrolled fire in combustible vegetation that occurs in the countryside or a wilderness area. Other names such as brush fire, bushfire, forest fire, desert fire, grass fire, hill fire, squirrel fire, vegetation fire, veldfire, and wilkjjofire may be used to describe the same...
generally has a positive effect on San Benito evening primrose by removing native and invasive vegetation. Prescribed fire is utilized by the Bureau of Land Management to control Centaurea solstitialis which once threatened to invade stream terrace habitat occupied by San Benito evening primrose near the confluence of Clear Creek and San Benito River. Some areas of geologic transition zone habitat on private land are grazed by cattle which like wildfire, is beneficial to San Benito evening primrose by removing competing vegetation, particularly invasive annual grasses.
The current estimated range for San Benito evening primrose is as follows:
- The northern limit of the species is Cerro Bonito south of Panoche Valley, and possibly as far north as Del Puerto Canyon.
- The southern edge of its distribution is around Priest Valley and Charley Mountain, possibly as far south as Table Mountain and ParkfieldParkfield, CaliforniaParkfield is an unincorporated community in Monterey County, California. It is located on Little Cholame Creek east of Bradley, at an elevation of 1529 feet...
. - The eastern limit is San Benito MountainSan Benito MountainSan Benito Mountain is a mountain located in the Diablo Range of California. The mountain, which rises to an elevation of , is the highest point in San Benito County and the Diablo Range and is also the highest point in the San Francisco Bay Area, though due to distance from other cities and the...
. This limit is quite certain because the nearest serpentine soil east of there is 150 kilometers away. - The western limit is the southern terminus of California State Route 25California State Route 25State Route 25 is a state highway in the U.S. state of California between Gilroy and State Route 198. This route is part of the California Freeway and Expressway System and is eligible for the State Scenic Highway System.-Route description:...
.
Population dynamics
San Benito evening primrose exhibits cyclic population dynamicsPopulation dynamics
Population dynamics is the branch of life sciences that studies short-term and long-term changes in the size and age composition of populations, and the biological and environmental processes influencing those changes...
with one cycle equal to 2 to 3 years. Total plant numbers for the species can fluctuate from a low of a few hundred plants to tens of thousands of plants during a cycle. The reason for the cycling is unknown but it may be related to predation
Predation
In ecology, predation describes a biological interaction where a predator feeds on its prey . Predators may or may not kill their prey prior to feeding on them, but the act of predation always results in the death of its prey and the eventual absorption of the prey's tissue through consumption...
by some type of insect
Insect
Insects are a class of living creatures within the arthropods that have a chitinous exoskeleton, a three-part body , three pairs of jointed legs, compound eyes, and two antennae...
that has a similar cycle. There is no obvious correlation with climate or human factors. Despite the cycling, the overall population remains stable and is slightly increasing.
San Benito evening primrose is well-buffered from extinction by enormous soil seed bank
Seed bank
Seed bank may refer to:*Seedbank, a repository of preserved seeds*The store of viable plant seed in an ecosystem; for example:** Soil seed bank, the viable seed present in the soil;...
100 - 1000 times that of the number of plants seen with a population in any given year. Seed in the soil seed bank has been documented to be viable for at least 20 years and likely is to be viable for much longer.
Conservation
The town of New Idria was founded in 1848 with the discovery of cinnabarCinnabar
Cinnabar or cinnabarite , is the common ore of mercury.-Word origin:The name comes from κινναβαρι , a Greek word most likely applied by Theophrastus to several distinct substances...
(mercury ore) within the New Idria serpentine mass (BLM Clear Creek Management Area). Numerous European prospectors and cattle ranchers settled throughout the area thereafter. Historic impacts to San Benito evening primrose have included logging
Logging
Logging is the cutting, skidding, on-site processing, and loading of trees or logs onto trucks.In forestry, the term logging is sometimes used in a narrow sense concerning the logistics of moving wood from the stump to somewhere outside the forest, usually a sawmill or a lumber yard...
and mining (gravel, magnesite
Magnesite
Magnesite is magnesium carbonate, MgCO3. Iron substitutes for magnesium with a complete solution series with siderite, FeCO3. Calcium, manganese, cobalt, and nickel may also occur in small amounts...
, chromite
Chromite
Chromite is an iron chromium oxide: FeCr2O4. It is an oxide mineral belonging to the spinel group. Magnesium can substitute for iron in variable amounts as it forms a solid solution with magnesiochromite ; substitution of aluminium occurs leading to hercynite .-Occurrence:Chromite is found in...
, cinnabar, and chrysotile asbestos). The relatively level stream terraces were historically favored by settlers for home sites and to stage industrial activities. A proposed mineral withdrawal for the New Idria serpentine mass will greatly limit any future mining in the area.
In more recent decades, the BLM Clear Creek Management Area became a popular motorized off-road vehicle
Off-road vehicle
An off-road vehicle is considered to be any type of vehicle which is capable of driving on and off paved or gravel surface. It is generally characterized by having large tires with deep, open treads, a flexible suspension, or even caterpillar tracks...
(ORV) recreation area. San Benito evening primrose was federally listed as Threatened in 1985. The primary threat cited by the Fish and Wildlife Service
United States Fish and Wildlife Service
The United States Fish and Wildlife Service is a federal government agency within the United States Department of the Interior dedicated to the management of fish, wildlife, and natural habitats...
was off-road vehicle
Off-road vehicle
An off-road vehicle is considered to be any type of vehicle which is capable of driving on and off paved or gravel surface. It is generally characterized by having large tires with deep, open treads, a flexible suspension, or even caterpillar tracks...
impacts to habitat. At the time, only nine populations of the species were known with most occurring on serpentine alluvial stream terraces within one of the highest ORV use areas at Clear Creek Manageemnt Area, Clear Creek Canyon. Nearly all of the stream terrace habitat in Clear Creek Canyon has since been fenced to exclude human impacts. A formal route designation in 2005 has further reduced ORV impacts.
The Clear Creek Management Area has been under a temporary Emergency Closure since May 1, 2008 when the Environmental Protection Agency reported that natural occurrences of chrysotile asbestos in the soil was above safe limits for people. As of February 2011, BLM lands within the area are still closed. The unmaintained public county road system through the area remains open.