''Potamogeton clystocarpus'' is a rare species of flowering plant in the pondweed family known by the common name Little Aguja pondweed. 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 ...

Texas Texas (, ; Spanish language, Spanish: ''Texas'', ''Tejas'') is a state in the South Central United States, South Central region of the United States. At 268,596 square miles (695,662 km2), and with more than 29.1 million residents in 2 ...

in the United States, where it is known only from one river canyon in Jeff Davis County. There is a single population of the

aquatic plant Aquatic plants are plants that have adapted to living in aquatic environments (saltwater or freshwater). They are also referred to as hydrophytes or macrophytes to distinguish them from algae and other microphytes. A macrophyte is a plant that ...

in Little Aguja Creek, and it has never been seen anywhere else. This is a federally listed

endangered species An endangered species is a species that is very likely to become extinct in the near future, either worldwide or in a particular political jurisdiction. Endangered species may be at risk due to factors such as habitat loss, poaching and inv ...

of the United States. This aquatic plant has a stem growing up to 57 centimeters long,''Potamogeton clystocarpus''.
Flora of North America. varying in length depending on the depth of the water.''Potamogeton clystocarpus''.
Texas Parks & Wildlife. The delicate, spirally arranged leaves are linear in shape and up to 7.8 centimeters in length by 1 or 2 millimeters wide. 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 the only part of the plant that is not submersed. It arises a few centimeters above the water's surface. The plant reproduces sexually via seed and

vegetatively Vegetative reproduction (also known as vegetative propagation, vegetative multiplication or cloning) is any form of asexual reproduction occurring in plants in which a new plant grows from a fragment or cutting of the parent plant or spec ...

via broken-off fragments of the stem, which can produce roots and anchor to form a new plant. Little else is known about the plant's life history.USFWS
''Potamogeton clystocarpus'' Recovery Plan.
June 1994. The plant has been noted and collected several times since its first collection in 1931. Though extremely restricted in distribution, it has usually appeared common to abundant in the one stream where it occurs. The Little Aguja Creek drains the

Davis Mountains The Davis Mountains, originally known as Limpia Mountains, are a range of mountains in West Texas, located near Fort Davis, after which they are named. The fort was named for then United States Secretary of War and later Confederate President Je ...

West Texas West Texas is a loosely defined region in the U.S. state of Texas, generally encompassing the arid and semiarid lands west of a line drawn between the cities of Wichita Falls, Abilene, and Del Rio. No consensus exists on the boundary betwee ...

. It is a very dynamic river, experiencing low levels during

drought A drought is defined as drier than normal conditions.Douville, H., K. Raghavan, J. Renwick, R.P. Allan, P.A. Arias, M. Barlow, R. Cerezo-Mota, A. Cherchi, T.Y. Gan, J. Gergis, D. Jiang, A. Khan, W. Pokam Mba, D. Rosenfeld, J. Tierney, an ...

, severe, scouring

flood A flood is an overflow of water ( or rarely other fluids) that submerges land that is usually dry. In the sense of "flowing water", the word may also be applied to the inflow of the tide. Floods are an area of study of the discipline hydrol ...

ing during high-drainage seasons, and changing

water quality Water quality refers to the chemical, physical, and biological characteristics of water based on the standards of its usage. It is most frequently used by reference to a set of standards against which compliance, generally achieved through tr ...

from chemical contamination and

livestock Livestock are the domesticated animals raised in an agricultural setting to provide labor and produce diversified products for consumption such as meat, eggs, milk, fur, leather, and wool. The term is sometimes used to refer solely to animals ...

upriver.''Potamogeton clystocarpus''.

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 ...

. In 1991 and 1992 heavy flooding scoured the canyon and the plant has not been seen since. Surveys have not relocated the plant.

References

{{Taxonbar, from=Q7234628 clystocarpus Flora of Texas Jeff Davis County, Texas