Physaria obcordata
Encyclopedia
Physaria obcordata is a rare species of flowering plant in the mustard family
known by the common names Dudley Bluffs twinpod and Piceance twinpod. It is endemic to Colorado
, where it is found only in the Piceance Basin
in Rio Blanco County
. It is threatened by the loss and degradation of its habitat. It is a federally listed threatened species of the United States.
This plant was discovered in 1982 and described to science in 1983. Its Piceance Basin habitat is open, barren, and made up of white shale
outcrops in the Green River Formation
. The topography
has been shaped by rivers cutting down through the substrate. Much of the rock is oil shale
covering deposits of natural gas
. Heavy petroleum exploration and extraction activities occur throughout the area, and the region is mined
for minerals such as nahcolite
and dawsonite
. This mining and surveying activity is the main threat to the species and its relative, the Dudley Bluffs bladderpod
(Lesquerella congesta). This threat is considered "imminent". 100% of the plant's habitat is potential territory for oil and mineral mining. The threat includes drilling activity as well as associated activities including road maintenance, pipeline installation, utilities, and construction of new housing and power plants. Increased pollution
and dust
may affect the plants.
The Dudley Bluffs twinpod is a perennial herb with a branching caudex
covered with the shredded remains of previous seasons' leaves. The erect stems grow 12 to 18 centimeters tall. The wide lance-shaped basal leaves are 4 to 8 centimeters long. The upper leaves are narrower but not much shorter. The inflorescence
is a loose raceme
of flowers with yellow-green sepal
s and yellow petals up to a centimeter in length. The heart-shaped fruit is a hanging, inflated silique
that is papery in texture and roughly half a centimeter long. The plant is pollinated
by bee
s of the genera Halictus
, Lasioglossum
, Dialictus, and Andrena
.
Though rare overall with a very small distribution, this plant is locally abundant, with 10,000 individuals at one site. There are ten occurrences and an estimated total of up to 27,800 individuals.
Brassicaceae
Brassicaceae, a medium sized and economically important family of flowering plants , are informally known as the mustards, mustard flowers, the crucifers or the cabbage family....
known by the common names Dudley Bluffs twinpod and Piceance twinpod. It is endemic to Colorado
Colorado
Colorado is a U.S. state that encompasses much of the Rocky Mountains as well as the northeastern portion of the Colorado Plateau and the western edge of the Great Plains...
, where it is found only in the Piceance Basin
Piceance Basin
The Piceance Basin is a geologic structural basin in northwestern Colorado, in the United States. It includes geologic formations from Cambrian to Holocene in age, but the thickest section is made up of rocks from the Cretaceous Period...
in Rio Blanco County
Rio Blanco County, Colorado
Rio Blanco County is the sixth most extensive of the 64 counties of the State of Colorado of the United States. The county population was 5,986 at U.S. Census 2000. The name of the county is the Spanish language name for the White River which runs through it...
. It is threatened by the loss and degradation of its habitat. It is a federally listed threatened species of the United States.
This plant was discovered in 1982 and described to science in 1983. Its Piceance Basin habitat is open, barren, and made up of white shale
Shale
Shale is a fine-grained, clastic sedimentary rock composed of mud that is a mix of flakes of clay minerals and tiny fragments of other minerals, especially quartz and calcite. The ratio of clay to other minerals is variable. Shale is characterized by breaks along thin laminae or parallel layering...
outcrops in the Green River Formation
Green River Formation
The Green River Formation is an Eocene geologic formation that records the sedimentation in a group of intermountain lakes. The sediments are deposited in very fine layers, a dark layer during the growing season and a light-hue inorganic layer in winter. Each pair of layers is called a varve and...
. The topography
Topography
Topography is the study of Earth's surface shape and features or those ofplanets, moons, and asteroids...
has been shaped by rivers cutting down through the substrate. Much of the rock is oil shale
Oil shale
Oil shale, an organic-rich fine-grained sedimentary rock, contains significant amounts of kerogen from which liquid hydrocarbons called shale oil can be produced...
covering deposits of natural gas
Natural gas
Natural gas is a naturally occurring gas mixture consisting primarily of methane, typically with 0–20% higher hydrocarbons . It is found associated with other hydrocarbon fuel, in coal beds, as methane clathrates, and is an important fuel source and a major feedstock for fertilizers.Most natural...
. Heavy petroleum exploration and extraction activities occur throughout the area, and the region is mined
Mining
Mining is the extraction of valuable minerals or other geological materials from the earth, from an ore body, vein or seam. The term also includes the removal of soil. Materials recovered by mining include base metals, precious metals, iron, uranium, coal, diamonds, limestone, oil shale, rock...
for minerals such as nahcolite
Nahcolite
Nahcolite is a soft, colourless or white carbonate mineral with the composition of sodium bicarbonate also called thermokalite. It crystallizes in the monoclinic system....
and dawsonite
Dawsonite
Dawsonite is a mineral composed of sodium aluminium carbonate hydroxide, chemical formula NaAlCO32. It crystallizes in the orthorhombic crystal system. It is not mined for ore. It was discovered in 1874 during the construction of the Redpath Museum in a feldspathic dike on the campus of McGill...
. This mining and surveying activity is the main threat to the species and its relative, the Dudley Bluffs bladderpod
Lesquerella congesta
Lesquerella congesta is a rare species of flowering plant in the mustard family known by the common name Dudley Bluffs bladderpod. It is endemic to western Colorado in the United States, where it is known only from seven occurrences in Rio Blanco County...
(Lesquerella congesta). This threat is considered "imminent". 100% of the plant's habitat is potential territory for oil and mineral mining. The threat includes drilling activity as well as associated activities including road maintenance, pipeline installation, utilities, and construction of new housing and power plants. Increased pollution
Pollution
Pollution is the introduction of contaminants into a natural environment that causes instability, disorder, harm or discomfort to the ecosystem i.e. physical systems or living organisms. Pollution can take the form of chemical substances or energy, such as noise, heat or light...
and dust
Dust
Dust consists of particles in the atmosphere that arise from various sources such as soil dust lifted up by wind , volcanic eruptions, and pollution...
may affect the plants.
The Dudley Bluffs twinpod is a perennial herb with a branching caudex
Caudex
A caudex is a form of stem morphology appearing as a thickened, short, perennial stem that is either underground or near ground level . It may be swollen for the purpose of water storage, especially in xerophytes...
covered with the shredded remains of previous seasons' leaves. The erect stems grow 12 to 18 centimeters tall. The wide lance-shaped basal leaves are 4 to 8 centimeters long. The upper leaves are narrower but not much shorter. 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 a loose raceme
Raceme
A raceme is a type of inflorescence that is unbranched and indeterminate and bears pedicellate flowers — flowers having short floral stalks called pedicels — along the axis. In botany, axis means a shoot, in this case one bearing the flowers. In a raceme, the oldest flowers are borne...
of flowers with yellow-green sepal
Sepal
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...
s and yellow petals up to a centimeter in length. The heart-shaped fruit is a hanging, inflated silique
Silique
A silique or siliqua is a fruit of 2 fused carpels with the length being more than three times the width. The outer walls of the ovary usually separate when ripe, leaving a persistent partition...
that is papery in texture and roughly half a centimeter long. The plant is 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 of the genera Halictus
Halictus
The genus Halictus is a large assemblage of bee species in the family Halictidae. The genus is divided into 15 subgenera, containing well over 300 species, primarily in the Northern Hemisphere...
, Lasioglossum
Lasioglossum
The sweat bee genus Lasioglossum is the largest of all bee genera, containing over seventeen hundred species in numerous subgenera worldwide. They are highly variable in size, coloration, and sculpture; among the more unusual variants, some are cleptoparasites, some are nocturnal, and some are...
, Dialictus, and Andrena
Andrena
Andrena is the largest genus in the family Andrenidae, and is nearly worldwide in distribution, with the notable exceptions of Oceania and South America. With over 1,300 species, it is one of the largest of all bee genera...
.
Though rare overall with a very small distribution, this plant is locally abundant, with 10,000 individuals at one site. There are ten occurrences and an estimated total of up to 27,800 individuals.