Johnston's Frankenia

Frankenia johnstonii

Description

The perennial Johnston's frankenia, Frankenia johnstonii, is a low-growing, sprawling shrub, reaching a typical height of about 12 in (31 cm. Under ideal conditions it may grow up to 2 ft (62 cm) tall. Numerous stems grow thickly from woody roots. Stems and leaves are gray-green to blue-green with a covering of short, white hairs. The narrow, oblong leaves average 0.5 in (13 mm) in length. This shrub displays single, white five-petaled flowers from September to May. Bees and flies are the main pollinators, but the reproductive potential of wild plants is uncertain as seedlings are very rarely observed.

Habitat

Johnston's frankenia occurs in relatively small populations in a highly specialized habitat. It is found on rocky hillsides in gypsum-rich soil or on salt flats in the most saline soils of the Maverick series in Texas and Mexico where the climate is hot and semi-arid. The species is an associate of mesquite and blackbrush scrub within the South Texas Plains vegetation zone.

Distribution

The historic range of this frankenia extended through Zapata and Starr counties, Texas, into adjacent Nuevo Leon, Mexico.

There are five known populations in extreme southern Texas (Starr and Zapata counties) on privately-owned grazing land. As of 1984, a site in Starr County supported 200-400 plants scattered over no more than 20 acres (8 hectares). Two other Starr County populations supported several hundred shrubs, each in an area of less than 2.5 acres (1 hectare). In Zapata County, one population contained 50-100 plants within an area of less than 1.25 acres (0.5 hectare). A second population known in this county has not been relocated despite an extensive search and may no longer exist.

A population of several hundred plants scattered over about 5 acres (2 hectares) of privately-owned land occurs in Nuevo Leon, Mexico, near Monterey.

Altogether, the 1993 population was estimated at 1,500 plants from seven sites. It is believed that there are several hundred plants in Mexico on 5 acres (2 hectares) of privately owned land.

Threats

All populations of Johnston's frankenia are found on marginal rangeland. Most surveyed plants show signs of being browsed by cattle, which seem to relish the plant's new growth. Grazing probably prevents new seedlings from becoming established. Shrubs and seedlings could also be damaged by locally used range management techniques, such as chaining, plowing, or bulldozing. Fencing population sites and removing livestock would prove a great benefit to the frankenia.

Johnston's frankenia reproduces poorly. In fact, annual surveys conducted since 1980 have found little or no evidence of natural reproduction. Because of low numbers, the shrub also suffers from a reduced gene pool and diminished genetic variability, which in turn reduces chances for the plant's survival.

Conservation and Recovery

Efforts to pollinate plants by hand have resulted in a less than 50% seed set—low, but still a considerable improvement over the natural rate. The approved Recovery Plan is expected to recommend an expansion of the pollination efforts.

Contact

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

References

Correll, D. S. 1966. " Frankenia johnstonii Correll sp. Nov." Rhodora 68:424-425.

Turner, B. L. 1980. "Status Report on Frankenia johnstonii Correll." Office of Endangered Species, U.S. Fish and Wildlife Service, Albuquerque.

U.S. Fish and Wildlife Service. 1986. "Johnston's Frankenia Recovery Plant, Technical/Agency Review Draft." Endangered Species Office, Albuquerque.

U.S. Fish and Wildlife Service. 1984. "Final Rule to Determine Frankenia johnstonii to Be an Endangered Species." Federal Register 49:31418-31421.