Lloyd's Mariposa Cactus

Echinomastus mariposensis

Description

Lloyd's mariposa cactus, Echinomastus mariposensis, grows as a single spherical or egg-shaped stem, about 3.5 in (9 cm) tall and 2 in (5 cm) in diameter. An immature plant begins with 13 smooth ribs and develops up to 21 wrinkled ribs as the plant matures. Spine clusters (areoles) consist of 26-32 short, off-white radial spines and from two to four tan central spines with blue or brown tips. Funnel-shaped, pinkish flowers, about 1.25 in (3.2 cm) in diameter, bloom in the spring. Yellowish green fruits are spherical or oblong and split open when ripe.

Other scientific appellations have been applied to this cactus, including Echinocactus mariposensis and Neolloydia mariposensis.

Habitat

A resident of the Chihuahuan Desert, this cactus grows on hills and lower slopes of very rocky, stable limestone gravel mesas in barren areas of thin soils overlaying hot, exposed limestone ridges. The habitat is 2,600-3,800 ft (790-1,160 m) in elevation.

Occurring in full sun in patches of limestone chips, the reflection from the white rocks raises the heat and light radiation to extremes. Rainfall averages 10-14 in (25-36 cm) annually.

Distribution

Lloyd's mariposa cactus is endemic to the Chihuahuan Desert, particularly Brewster and Presidio counties, Texas, and probably to northern Coahuila, Mexico. It has been found in low numbers along the Rio Grande River from Reagan Canyon in the east (Brewster County) to the Bofecillos Mountains in the west (Presidio County). Most populations occur on private land, although some plants are found within the Big Bend National Park. The plant's range almost certainly extends southward into Mexico, but the status of the Mexican population is unknown.

Threats

Lloyd's mariposa cactus declined in the 1940s when mining for mercury ore destroyed large sections of its habitat. Surviving plants are now widely scattered. Many plants have been destroyed or damaged by heavy livestock grazing in the dry, marginal habitat. Livestock-induced erosion has more recently been worsened by the intrusion of off-road vehicles, used as recreation or to develop mineral claims.

The habitat areas near Terlingua and Lajitas, Texas are being developed for resort homes; the populations at Dove Mountain, Reagan Canyon, and Big Canyon are subject to livestock grazing; and the Big Bend National Park population is exposed to camping, hiking, and road maintenance. As a rare show specimen, this cactus is always subject to collection.

Conservation and Recovery

This cactus has been collected in its more accessible locations, but the remoteness of most sites and its scattered distribution give it some protection. Collecting is prohibited within the Big Bend National Park, although enforcement is difficult. The cactus is protected by Texas laws, but there are no effective prohibitions against taking plants from private land with the landowners' permission.

Currently, the population is small but appears stable. The U. S. Fish and Wildlife Service (FWS) personnel will continue to monitor populations on a regular basis but will undertake no active recovery measures unless numbers decline steeply or unless a more immediate threat, such as coal or oil development, appears. The two known populations occur within Big Bend National Park on private lands mostly owned by the Lajita Museum and Desert Garden, which has an active interest in preserving the species.

The FWS recommends studying the soil and water requirements of the species, the role of animals in seed dispersal, habitat factors affecting seed dispersal, pollinators, and population dynamics. With this data, additional habitat areas might be established and populated.

Contact

Regional Office of Endangered Species
U.S. Fish and Wildlife Service
P.O. Box 1306
Albuquerque, New Mexico 87103
http://southwest.fws.gov/

References

Benson, L. 1982. The Cacti of the United States and Canada. Stanford University Press, Stanford, California.

U.S. Fish and Wildlife Service. 1987. "Endangered and Threatened Species of Texas and Oklahoma (with 1988 Addendum)." U.S. Fish and Wildlife Service, Albuquerque.

U.S. Fish and Wildlife Service. 1987. "Lloyd's Mariposa Cactus Recovery Plan." U.S. Fish and Wildlife Service, Albuquerque. 35 pp.