''Physaria obcordata'' is a rare species of flowering plant in the family Brassicaceae known by the common name Dudley Bluffs twinpod. It is similar in appearance to the more common Piceance twinpod, but can be distinguished by looking at the leaves through a hand lens. The Piceance twinpod, ''Physaria acutifolia'' has stellate hairs when viewed through a hand lens while ''Physaria ocordata'' has markings that look like a satellite dish, or a circle with a dot in the middle. It is

endemic Endemism is the state of a species being found in a single defined geographic location, such as an island, state, nation, country or other defined zone; organisms that are indigenous to a place are not endemic to it if they are also found elsew ...

Colorado Colorado (, other variants) is a state in the Mountain West subregion of the Western United States. It encompasses most of the Southern Rocky Mountains, as well as the northeastern portion of the Colorado Plateau and the western edge of t ...

, where it is found only in the

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. The basi ...

in Rio Blanco County.''Physaria obcordata''.

The Nature Conservancy The Nature Conservancy (TNC) is a global environmental organization headquartered in Arlington, Virginia. it works via affiliates or branches in 79 countries and territories, as well as across every state in the US. Founded in 1951, The Natu ...

. 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.Rollins, R. C. (1983). Studies in the Cruciferae of western North America. ''Journal of the Arnold Arboretum of Harvard University''. 64(4) 491-501 Its Piceance Basin habitat is open, barren, and made up of white

shale Shale is a fine-grained, clastic sedimentary rock formed from mud that is a mix of flakes of clay minerals (hydrous aluminium phyllosilicates, e.g. kaolin, Al2 Si2 O5( OH)4) and tiny fragments (silt-sized particles) of other minerals, especial ...

outcrops in the

Green River Formation The Green River Formation is an Eocene geologic formation that records the sedimentation in a group of intermountain lakes in three basins along the present-day Green River in Colorado, Wyoming, and Utah. The sediments are deposited in very fine ...

. The

topography Topography is the study of the forms and features of land surfaces. The topography of an area may refer to the land forms and features themselves, or a description or depiction in maps. Topography is a field of geoscience and planetary sci ...

has been shaped by rivers cutting down through the substrate. Much of the rock is oil shale covering deposits of

natural gas Natural gas (also called fossil gas or simply gas) is a naturally occurring mixture of gaseous hydrocarbons consisting primarily of methane in addition to various smaller amounts of other higher alkanes. Low levels of trace gases like carbo ...

. Heavy petroleum exploration and extraction activities occur throughout the area, and the region is mined for minerals such as

nahcolite Nahcolite is a soft, colourless or white carbonate mineral with the composition of sodium bicarbonate ( Na H C O3) also called thermokalite. It crystallizes in the monoclinic system. Nahcolite was first described in 1928 for an occurrence in a ...

and

dawsonite Dawsonite is a mineral composed of sodium aluminium carbonate hydroxide, chemical formula NaAlCO3(OH)2. It crystallizes in the orthorhombic crystal system. It is not mined for ore. It was discovered in 1874 during the construction of the Redpath ...

.USFWS
''Dudley Bluffs bladderpod and Dudley Bluffs twinpod Five-year Review.
June 2008. This mining and surveying activity is the main threat to the species''Physaria obcordata''.
Center for Plant Conservation. and its relative, the Dudley Bluffs bladderpod (''Physaria 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 is the introduction of contaminants into the natural environment that cause adverse change. Pollution can take the form of any substance (solid, liquid, or gas) or energy (such as radioactivity, heat, sound, or light). Pollutants, the ...

and

dust Dust is made of fine particles of solid matter. On Earth, it generally consists of particles in the atmosphere that come from various sources such as soil lifted by wind (an aeolian process), volcanic eruptions, and pollution. Dust in homes ...

may affect the plants. The Dudley Bluffs twinpod is a perennial herb with a branching

caudex A caudex (plural: caudices) of a plant is a stem, but the term is also used to mean a rootstock and particularly a basal stem structure from which new growth arises.pages 456 and 695 In the strict sense of the term, meaning a stem, "caudex" is m ...

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 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. Morphologically, it is the modified part of the shoot of seed plants where flowers are formed o ...

is a loose

raceme A raceme ( or ) or racemoid is an unbranched, indeterminate type of inflorescence bearing flowers having short floral stalks along the shoots that bear the flowers. The oldest flowers grow close to the base and new flowers are produced as the s ...

of flowers with yellow-green

sepal A sepal () is a part of the flower of angiosperms (flowering plants). Usually green, sepals typically function as protection for the flower in bud, and often as support for the petals when in bloom., p. 106 The term ''sepalum'' was coined b ...

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.''Physaria obcordata''.
Flora of North America. The plant is pollinated by

bee Bees are winged insects closely related to wasps and ants, known for their roles in pollination and, in the case of the best-known bee species, the western honey bee, for producing honey. Bees are a monophyly, monophyletic lineage within the ...

s of the genera ''

Halictus The genus ''Halictus'' is a large assemblage of bee species in the family Halictidae. The genus is divided into 15 subgenera, some of dubious monophyly, containing over 200 species, primarily in the Northern Hemisphere (a few species occur in Sou ...

'', ''

Lasioglossum The sweat bee genus ''Lasioglossum'' is the largest of all bee genera, containing over 1700 species in numerous subgenera worldwide.Gibbs, J., et al. (2012)Phylogeny of halictine bees supports a shared origin of eusociality for ''Halictus'' an ...

'', ''

Dialictus ''Dialictus'' is a subgenus of sweat bees belonging to the genus ''Lasioglossum''. Most of the members of this subgenus have a metallic appearance, while some are non-metallic. There are over 630 species worldwide. They are commonly found in the ...

'', 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.

References

External links

USDA Plants Profile for ''Physaria obcordata''
{{Taxonbar, from=Q7189517 obcordata Flora of Colorado Endemic flora of the United States Rio Blanco County, Colorado Critically endangered flora of the United States Plants described in 1983