Cochise Pincushion Cactus

Coryphantha robbinsorum

Description

Cochise pincushion cactus, Coryphantha robbinsorum, is a small, spiny, unbranched cactus that, as its name implies, resembles a founded pincushion. It lacks central spines and typically has 11-17 sharp, radial spines. The flowers, which appear in March and April, are a pale yellow-green with a slight bronze cast. Fruits ripen to orange-red in July and August, but quickly turn a dull red.

Most of the stem is underground, with usually only 0.4 in (1 cm) protruding above ground level. During the spring and fall, when droughts normally occur, the plants shrink. The proportion of plant exposed during drought periods depends on the microsite. Plants growing on bedrock will shrink during droughts but cannot retract into the soil. In microsites with some accumulated soil, the plant surface can be flush with the substrate surface when retracted.

This species has a much lower reproductive potential than other related cacti. Each plant produces an average of three fruits annually, each containing about 20 seeds. A dynamic balance between the disappearance of colonies from localized sites and the emergence of new colonies nearby seems a natural feature of its biology.

The species has been known by two other scientific names: Cochiseia robbinsorum Earle, and Escobaria robbinsorum.

Habitat

This pincushion cactus grows in semidesert grassland on limestone hills at an elevation of 4,200 ft (1,280 m). Dominant associated species are sandpaper bush, ocotillo, desert spoon, snakeweed, Palmer agave, amole, and prickly pear.

Distribution

The Cochise pincushion cactus is endemic to the Sonoran Desert of southwestern Arizona and Mexico. Reports of populations in neighboring Sonora, Mexico, would suggest that this cactus was once distributed over a wider area. Today, it is found on several isolated hills in Cochise County, Arizona, at sites averaging about 2.5 acres (1 hectare) each. Density of plants on these limestone hills varies greatly. Plants are rare and scattered throughout most of the hilly area but small, isolated clusters of 100-1,000 plants occur sporadically.

All known populations are on privately owned ranchland or public land held in trust and managed by the Arizona State Land Department. A population has been reported in adjacent Sonora, Mexico, but its status is unknown. There are no current population estimates, other than an indication that numbers are low.

Threats

The bulk of the Cochise County population is located on an active cattle ranch. Cattle have been known to graze on and trample this species. Limestone quarrying and oil drilling in the habitat are also potential threats to the cactus. Quarries are currently active in the region, and new areas are slated for mineral development.

Significant climatic changes can also affect the cactus; several researchers involved in the annual U. S. Fish and Wildlife Service (FWS) monitoring project during the late 1980s and early 1990s observed during data collection that many plants appeared stressed, and it was concluded that lower-than-average rainfalls during the winters of 1987 through 1991 were probably responsible for the stress to the plants.

Predation is another threat. Insects, such as cactus specialist moths (which use the plants as larval food, frequently killing the host plant) and large cactus specialist beetles (which always kill the host plant), are a real danger to the cactus. Mammal predators who feed on the cactus include the woodrat and other rodents, rabbits and javelina.

Because of its size, rarity, and beauty, Cochise pincushion cactus is sought by plant collectors. If collectors are patient, however, they will not have to contribute to the species' decline by taking collecting wild plants. The cactus has been successfully propagated in the greenhouse, and seeds as well as cultivated plants will be made commercially available within the next few years.

Conservation and Recovery

The FWS published its recovery plan for the Cochise pincushion cactus in 1993, calling for a number of actions, including the stricter enforcement of laws banning collection and trade. Other recovery efforts deemed necessary to achieve the goal of delisting the species within a decade include the development and implementation of a habitat management plan in cooperation with private and state landowners; the study of population biology to determine the effects of management; protection from loss of individuals and habitat; and the establishment of conservation and research programs. The plan also calls for the definition of range and distribution of Cochise pincushion cactus and biological studies necessary for effective species management.

The 1993 plan notes that recovery of the species will require permanent protection and management of the habitat, trade protection through retention of the species on the Highly Safeguarded Lists of the Arizona Native Plant Law and CITES list following delisting, and demonstration through years of monitoring that viable populations are being maintained.

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

Earle, W. H. 1976. "Cochiseia Earle, Genus Novum."Saguaroland Bulletin 30:65-66.

Lopresti, V. 1984. "Coryphantha robbinsorum in Mexico." Cactus and Succulent Journal of Mexico29:81.

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

U.S. Fish and Wildlife Service. 1993. "Chochise Pincushion Cactus Recovery Plan." U.S. Fish and Wildlife Service, Albuquerque.

Zimmerman, A. D. 1978. "The Relationships ofCochiseia robbinsorum Earle." Cactus and Succulent Journal (U.S.) 50:293-297.