Otay Mesa Mint

Pogogyne nudiuscula

Description

Otay mesa mint, Pogogyne nudiuscula, is an annual herb in the mint family (Lamiaceae). It can reach 12 in (30 cm) or more in height, has bright green leaves, and typically blooms from May or June through early July. The plant usually does not have many branches, and the vegetative and floral portions of the plant give off a strong, turpentine mint odor. In contrast to P. abramsii the vegetative portions of the plant do not develop a reddish tinge until the plant is past the flowering period. The flowers are purple with a white throat. P. nudiuscula typically has six flowers (occasionally more) per stem node, a glabrous to minutely pubescent (hairy) calyx, and bracts and leaves that are wider than P. abramsii.

Habitat

The species occurs in vernal pools which form in areas with Mediterranean climates where slight depressions become seasonally wet or inundated following fall and winter rains. Water remains in these pools for a few months at a time, due to an impervious layer such as hard pan, clay, or basalt beneath the soil surface. Gradual drying occurs during the spring. The pools form on mesa tops or valley floors and are interspersed among very low hills usually referred to as mima mounds.

Distribution

Otay Mesa mint once occurred from Otay Mesa of San Diego County to immediately south of the international border in Baja California, Mexico. The historic range may have extended to the mesas east of Balboa Park and south of Mission Valley in San Diego where vernal pools contain P. abramsii, another endangered vernal pool plant. The species was never known to occur further north than Otay Mesa. The sites in extreme northern Baja California, Mexico—where the Tijuana International Airport is now located—were very likely extirpated.

As of the late 1990s, P. nudiuscula existed only in seven vernal pool complexes on Otay Mesa. The species' numbers were low and scattered across its range.

A large population of Pogogyne was found in 1995 by Reid Moran in Valle de las Palmas, in Baja California, Mexico, about 20 mi (32 km) south of the Tecate Border crossing; this population, however, is considered a unique species. It can be distinguished from P. nudiuscula on Otay Mesa by the calyx to corolla ratio, the number of flowers per node, and the general size of the floral parts.

Threats

The U. S. Fish and Wildlife Service determined that the species' range was being rapidly reduced and that the continued existence of the species was threatened by habitat loss and degradation due to urban and agricultural development, livestock grazing, off-road vehicle use, trampling, invasions from weedy non-native plants, road development, military activities, and water management activities. The recovery priority of 2C indicates that it is a species facing a high degree of threat but has a high potential for recovery. The species may, however, be in conflict with construction or development projects. Many pool groups were entirely eliminated and replaced with urban or agricultural developments.

Conservation and Recovery

P. nudiuscula was listed by the State of California as endangered in July 1987, under the California Endangered Species Act, and is currently recognized as such.

Contacts

U. S. Fish and Wildlife Service
Regional Office, Division of Endangered Species
Eastside Federal Complex
911 N. E. 11th Ave.
Portland, Oregon 97232-4181
Telephone: (503) 231-6121
http://pacific.fws.gov/

U. S. Fish and Wildlife Service
Sacramento Fish and Wildlife Office
2800 Cottage Way, Room W-2605
Sacramento, California 98525-1846
Telephone: (916) 414-6600
Fax: (916) 460-4619

U. S. Fish and Wildlife Service
Ventura Fish and Wildlife Office
2493 Portola Rd., Suite B
Ventura, California 93003-7726
Telephone: (805) 644-1766

References

U. S. Fish and Wildlife Service. 3 August 1993. "Endangered Status for Three Vernal Pool Plants and the Riverside Fairy Shrimp." Federal Register 58 (147): 41384-41392.

U. S. Fish and Wildlife Service. 1998. "Recovery Plan for Vernal Pools of Southern California." U. S. Fish and Wildlife Service, Portland. 160 pp.