Deinandra conjugens
Encyclopedia
Deinandra conjugens is a rare species of flowering plant in the aster family
known by the common names Otay tarplant and Otay tarweed. It is native to a small section of far northern Baja California
in Mexico, its range extending north into San Diego County, California
, in the United States. It is threatened by habitat destruction
and degradation. It was federally listed as a threatened species in 1998.
This is an annual herb growing up to about half a meter in maximum height with a solid, bristly, gland-dotted stem. The lower leaves are hairy and lobed or toothed, and measure up to about 4.5 centimeters long. The inflorescence
is made up of one or more flower heads
, sometimes with many heads in clusters. The underside of the head is covered in phyllaries
with many glands. Each head has 7 to 10 yellow ray florets no more than 6 millimeters long. Most ray florets have three tiny lobes at the tips. The center of the head is filled with yellow disc florets tipped with black, dark purple or red anthers
. The flowers are most often pollinated
by bee
s. The fruit is an achene
. The achenes arising from the disc florets have pappi
of white scales. Disc achenes germinate
sooner than those from ray florets. Many achenes drop into the soil seed bank
.
Most of the known occurrences of this plant are in San Diego County in the United States. They are located in the southern part of the county in areas such as Otay Mesa and Proctor Valley
. The city of San Diego
has a conservation plan for this species and monitors it. There are about 34 to 37 occurrences remaining; some known occurrences are thought to have been extirpated
since the plant was federally listed. It grows in clay
soils in several types of habitat, including grassland
and maritime
and inland coastal sage scrub
. It tolerates some disturbance in its habitat, and low levels of grazing
and road maintenance activities such as mowing
are probably beneficial.
The region in which the plant lives is heavily impacted by development and other processes and exists now in a fragmented
state. 70% of the plant's habitat within its range has been destroyed. Much of the territory previously threatened by development has been conserved
within a number of reserves
. Many are protected under a San Diego county ordinance
. The San Diego National Wildlife Refuge
created the Otay Tarplant Preserve and Caltrans
reserved a section of land for the plant near a busy highway. While many California populations are now protected, there are still many that are in danger of destruction. The status and distribution of this plant within Mexico are unknown.
Besides outright habitat destruction, the plant is affected by several processes of habitat degradaton. Introduced weeds
have invaded
the habitat, including brome grasses
(Bromus spp.), wild oats
(Avena spp.), and ryegrass
(Lolium perenne). Off-road vehicle
s are used on some land that contains the plant, and trash
dumping has been known to occur. The maintenance of rural roads that lead to utility outposts may affect the land. Many occurrences are near the international border, and Border Patrol
activities affect the habitat there.
Asteraceae
The Asteraceae or Compositae , is an exceedingly large and widespread family of vascular plants. The group has more than 22,750 currently accepted species, spread across 1620 genera and 12 subfamilies...
known by the common names Otay tarplant and Otay tarweed. It is native to a small section of far northern Baja California
Baja California
Baja California officially Estado Libre y Soberano de Baja California is one of the 31 states which, with the Federal District, comprise the 32 Federal Entities of Mexico. It is both the northernmost and westernmost state of Mexico. Before becoming a state in 1953, the area was known as the North...
in Mexico, its range extending north into San Diego County, California
San Diego County, California
San Diego County is a large county located in the southwestern corner of the US state of California. Hence, San Diego County is also located in the southwestern corner of the 48 contiguous United States. Its county seat and largest city is San Diego. Its population was about 2,813,835 in the 2000...
, in the United States. It is threatened by habitat destruction
Habitat destruction
Habitat destruction is the process in which natural habitat is rendered functionally unable to support the species present. In this process, the organisms that previously used the site are displaced or destroyed, reducing biodiversity. Habitat destruction by human activity mainly for the purpose of...
and degradation. It was federally listed as a threatened species in 1998.
This is an annual herb growing up to about half a meter in maximum height with a solid, bristly, gland-dotted stem. The lower leaves are hairy and lobed or toothed, and measure up to about 4.5 centimeters long. The 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...
is made up of one or more flower heads
Head (botany)
The capitulum is considered the most derived form of inflorescence. Flower heads found outside Asteraceae show lesser degrees of specialization....
, sometimes with many heads in clusters. The underside of the head is covered in phyllaries
Bract
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...
with many glands. Each head has 7 to 10 yellow ray florets no more than 6 millimeters long. Most ray florets have three tiny lobes at the tips. The center of the head is filled with yellow disc florets tipped with black, dark purple or red anthers
Stamen
The stamen is the pollen producing reproductive organ of a flower...
. The flowers are most often pollinated
Pollination
Pollination is the process by which pollen is transferred in plants, thereby enabling fertilisation and sexual reproduction. Pollen grains transport the male gametes to where the female gamete are contained within the carpel; in gymnosperms the pollen is directly applied to the ovule itself...
by bee
Bee
Bees are flying insects closely related to wasps and ants, and are known for their role in pollination and for producing honey and beeswax. Bees are a monophyletic lineage within the superfamily Apoidea, presently classified by the unranked taxon name Anthophila...
s. The fruit is an achene
Achene
An achene is a type of simple dry fruit produced by many species of flowering plants. Achenes are monocarpellate and indehiscent...
. The achenes arising from the disc florets have pappi
Pappus (flower structure)
The pappus is the modified calyx, the part of an individual disk, ray or ligule floret surrounding the base of the corolla, in flower heads of the plant family Asteraceae. The pappus may be composed of bristles , awns, scales, or may be absent. In some species, the pappus is too small to see...
of white scales. Disc achenes 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...
sooner than those from ray florets. Many achenes drop into the soil seed bank
Soil Seed Bank
The soil seed bank refers to the natural storage of seeds, often dormant, within the soil of most ecosystems. The study of soil seed banks started in 1859 when Charles Darwin observed the emergence of seedlings using soil samples from the bottom of a lake. The first scientific paper on the subject...
.
Most of the known occurrences of this plant are in San Diego County in the United States. They are located in the southern part of the county in areas such as Otay Mesa and Proctor Valley
Proctor Valley
Proctor Valley is a region in the southeast corner of San Diego County, California, in the United States. Proctor Valley Road runs through the valley and connects Jamul to Eastlake. This area, which is home to myriad unique forms of plant and animal life, is quickly being consumed by suburban...
. The city of San Diego
San Diego, California
San Diego is the eighth-largest city in the United States and second-largest city in California. The city is located on the coast of the Pacific Ocean in Southern California, immediately adjacent to the Mexican border. The birthplace of California, San Diego is known for its mild year-round...
has a conservation plan for this species and monitors it. There are about 34 to 37 occurrences remaining; some known occurrences are thought to have been extirpated
Local extinction
Local extinction, also known as extirpation, is the condition of a species which ceases to exist in the chosen geographic area of study, though it still exists elsewhere...
since the plant was federally listed. It grows in 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...
soils in several types of habitat, including 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...
and maritime
Coast
A coastline or seashore is the area where land meets the sea or ocean. A precise line that can be called a coastline cannot be determined due to the dynamic nature of tides. The term "coastal zone" can be used instead, which is a spatial zone where interaction of the sea and land processes occurs...
and inland coastal sage scrub
Coastal sage scrub
Coastal sage scrub is a low scrubland plant community found in the California chaparral and woodlands ecoregion of coastal California and northern Baja California. It is characterized by low-growing aromatic, and drought-deciduous shrubs adapted to the semi-arid Mediterranean climate of the...
. It tolerates some disturbance in its habitat, and low levels of grazing
Grazing
Grazing generally describes a type of feeding, in which a herbivore feeds on plants , and also on other multicellular autotrophs...
and road maintenance activities such as mowing
Mower
A mower is a machine for cutting grass or other plants that grow on the ground. Usually mowing is distinguished from reaping, which uses similar implements, but is the traditional term for harvesting grain crops, e.g...
are probably beneficial.
The region in which the plant lives is heavily impacted by development and other processes and exists now in a fragmented
Habitat fragmentation
Habitat fragmentation as the name implies, describes the emergence of discontinuities in an organism's preferred environment , causing population fragmentation...
state. 70% of the plant's habitat within its range has been destroyed. Much of the territory previously threatened by development has been conserved
Habitat conservation
Habitat conservation is a land management practice that seeks to conserve, protect and restore, habitat areas for wild plants and animals, especially conservation reliant species, and prevent their extinction, fragmentation or reduction in range...
within a number of reserves
Nature reserve
A nature reserve is a protected area of importance for wildlife, flora, fauna or features of geological or other special interest, which is reserved and managed for conservation and to provide special opportunities for study or research...
. Many are protected under a San Diego county ordinance
Local ordinance
A local ordinance is a law usually found in a municipal code.-United States:In the United States, these laws are enforced locally in addition to state law and federal law.-Japan:...
. The San Diego National Wildlife Refuge
San Diego National Wildlife Refuge
San Diego National Wildlife Refuge is a National Wildlife Refuge in California. It is part of the San Diego National Wildlife Refuge Complex.A variety of habitats from coastal sage scrub and chaparral to oak woodland and freshwater marsh describe this inland refuge in San Diego's backcountry.The...
created the Otay Tarplant Preserve and Caltrans
California Department of Transportation
The California Department of Transportation is a government department in the U.S. state of California. Its mission is to improve mobility across the state. It manages the state highway system and is actively involved with public transportation systems throughout the state...
reserved a section of land for the plant near a busy highway. While many California populations are now protected, there are still many that are in danger of destruction. The status and distribution of this plant within Mexico are unknown.
Besides outright habitat destruction, the plant is affected by several processes of habitat degradaton. Introduced weeds
Introduced species
An introduced species — or neozoon, alien, exotic, non-indigenous, or non-native species, or simply an introduction, is a species living outside its indigenous or native distributional range, and has arrived in an ecosystem or plant community by human activity, either deliberate or accidental...
have invaded
Invasive species
"Invasive species", or invasive exotics, is a nomenclature term and categorization phrase used for flora and fauna, and for specific restoration-preservation processes in native habitats, with several definitions....
the habitat, including brome grasses
Bromus
Bromus is a large genus of the grass family . Estimates in the scientific literature of the number of species have ranged from 100 to 400, but plant taxonomists currently recognize around 160–170 species...
(Bromus spp.), wild oats
Avena
The oats are a genus of 10-15 species of true grasses . They are native to Europe, Asia and northwest Africa. One species is widely cultivated elsewhere, and several have become naturalized in many parts of the world...
(Avena spp.), and ryegrass
Lolium perenne
Lolium perenne, common name Perennial Ryegrass, is a grass from the family Poaceae. It is native to Europe, Asia and northern Africa, but is widely cultivated and naturalised around the world.-Description:...
(Lolium perenne). 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...
s are used on some land that contains the plant, and trash
Waste
Waste is unwanted or useless materials. In biology, waste is any of the many unwanted substances or toxins that are expelled from living organisms, metabolic waste; such as urea, sweat or feces. Litter is waste which has been disposed of improperly...
dumping has been known to occur. The maintenance of rural roads that lead to utility outposts may affect the land. Many occurrences are near the international border, and Border Patrol
United States Border Patrol
The United States Border Patrol is a federal law enforcement agency within U.S. Customs and Border Protection , a component of the Department of Homeland Security . It is an agency in the Department of Homeland Security that enforces laws and regulations for the admission of foreign-born persons to...
activities affect the habitat there.