Ambrosia cheiranthifolia
Encyclopedia
Ambrosia cheiranthifolia is a rare species of flowering plant known by the common names South Texas ambrosia and Rio Grande ragweed. It is native to the coast of South Texas
and the Mexican state of Tamaulipas
, where it occurs in coastal prairie
, grassland
, and mesquite
shrubland habitat. It has declined because its native habitat has been cleared for development, with remaining open savanna
invaded by non-native grasses
such as buffelgrass (Cenchrus ciliaris). Today there are perhaps 20 populations remaining, but some of these may have very few genetic individuals because the species is clonal
, with many cloned plants attached by one rhizome
. It is not certain that the plant still exists in Mexico. This is a federally listed endangered species
of the United States.
This is a rhizomatous perennial herb growing erect to a maximum height around 40 centimeters. Several clones usually grow in a dense patch. The stems and herbage are silvery green with a coating of rough gray hairs. The oblong leaves are 3 to 7 centimeters long and oppositely arranged on the lower plant but alternate on the upper stems. The inflorescence
contains staminate
flower heads
in clusters with a few pistillate
heads in leaf axils below the clusters.
This plant sometimes occurs alongside slender rush-pea
(Hoffmannseggia tenella), another endangered species.
South Texas
South Texas is a region of the U.S. state of Texas that lies roughly south of and including San Antonio. The southern and western boundary is the Rio Grande River, and to the east it is the Gulf of Mexico. The population of this region is about 3.7 million. The southern portion of this region is...
and the Mexican state of Tamaulipas
Tamaulipas
Tamaulipas officially Estado Libre y Soberano de Tamaulipas is one of the 31 states which, with the Federal District, comprise the 32 Federal Entities of Mexico. It is divided in 43 municipalities and its capital city is Ciudad Victoria. The capital city was named after Guadalupe Victoria, the...
, where it occurs in coastal prairie
Coastal prairie
Coastal prairie may refer to either:* The California coastal prairie, a plant community found along the coasts of California and Oregon* The Western Gulf coastal grasslands of Louisiana, Texas, and Tamaulipas...
, 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 mesquite
Mesquite
Mesquite is a leguminous plant of the Prosopis genus found in northern Mexico through the Sonoran Desert and Chihuahuan Deserts, and up into the Southwestern United States as far north as southern Kansas, west to the Colorado Desert in California,and east to the eastern fifth of Texas, where...
shrubland habitat. It has declined because its native habitat has been cleared for development, with remaining open savanna
Savanna
A savanna, or savannah, is a grassland ecosystem characterized by the trees being sufficiently small or widely spaced so that the canopy does not close. The open canopy allows sufficient light to reach the ground to support an unbroken herbaceous layer consisting primarily of C4 grasses.Some...
invaded by non-native grasses
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...
such as buffelgrass (Cenchrus ciliaris). Today there are perhaps 20 populations remaining, but some of these may have very few genetic individuals because the species is clonal
Cloning
Cloning in biology is the process of producing similar populations of genetically identical individuals that occurs in nature when organisms such as bacteria, insects or plants reproduce asexually. Cloning in biotechnology refers to processes used to create copies of DNA fragments , cells , or...
, with many cloned plants attached by one rhizome
Rhizome
In botany and dendrology, a rhizome is a characteristically horizontal stem of a plant that is usually found underground, often sending out roots and shoots from its nodes...
. It is not certain that the plant still exists in Mexico. This is a federally listed endangered species
Endangered species
An endangered species is a population of organisms which is at risk of becoming extinct because it is either few in numbers, or threatened by changing environmental or predation parameters...
of the United States.
This is a rhizomatous perennial herb growing erect to a maximum height around 40 centimeters. Several clones usually grow in a dense patch. The stems and herbage are silvery green with a coating of rough gray hairs. The oblong leaves are 3 to 7 centimeters long and oppositely arranged on the lower plant but alternate on the upper stems. 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...
contains staminate
Stamen
The stamen is the pollen producing reproductive organ of a flower...
flower heads
Head (botany)
The capitulum is considered the most derived form of inflorescence. Flower heads found outside Asteraceae show lesser degrees of specialization....
in clusters with a few pistillate
Gynoecium
Gynoecium is most commonly used as a collective term for all carpels in a flower. A carpel is the ovule and seed producing reproductive organ in flowering plants. Carpels are derived from ovule-bearing leaves which evolved to form a closed structure containing the ovules...
heads in leaf axils below the clusters.
This plant sometimes occurs alongside slender rush-pea
Hoffmannseggia tenella
Hoffmannseggia tenella is a rare species of flowering plant in the legume family known by the common name slender rushpea. It is endemic to Texas, where it is known from only two counties. It persists in small remnants of its gulf coastal prairie habitat...
(Hoffmannseggia tenella), another endangered species.