Lobelia oahuensis

No Common Name

Description

Lobelia oahuensis is a stout, erect, and unbranched shrub in the bellflower family that reaches a height of 3-10 ft (0.9-3.0 m). The elliptic leaves, 16-24 in (40.6-60.9 cm) long and 1.6-2.4 in (4.1-6.1 cm) wide, are typically stalkless and form a very dense rosette at the end of the stem. The upper surface of the leaves is hairless and the lower surface is covered with rather coarse, grayish or greenish hairs. The inflorescence is branched three to five times from its base, with each erect spike 3-5 ft (0.9-1.5 m) tall and comprised of 50-200 flowers. Each flower measures 1.7-1.8 in (4.3-4.6 cm) long and about 0.2 in (0.5 cm) wide, with a 1.2-in (3.1-cm) long bract just below it. The linear calyx lobes are about 0.6 in (1.5 cm) long and 0.1 in (0.3 cm) wide. The fruits, 0.4-0.7 in (1.1 cm-1.8 cm) long and about 0.4 in (1.1 cm) wide, are hairy, oval capsules that contain numerous brownish seeds. This species was observed in flower during November 1991.

L. oahuensis differs from other members of the genus in having erect stems 3-10 ft (0.9-3.0 m) long, dense rosettes of leaves at the end of stems, lower leaf surfaces covered with coarse grayish or greenish hairs, and flowers 1.7-1.8 in (4.3-4.6 cm) long.

Habitat

L. oahuensis grows on tree trunks on summit cliffs in 'ohi'a-dominated, cloud-swept wet forests or in areas of low shrub cover that are frequently exposed to heavy wind and rain. The 11 populations occur at elevations between 2,800 and 3,500 ft (853.4 and 1,066.8 m). The vegetation in those areas usually includes kanawao, uluhe, 'uki, hame, and kopiko.

Distribution

L. oahuensis had historical occurrences on Oahu from Kahana Ridge, Kipapa Gulch, and the southeastern Koolau Mountains. The species currently grows on steep slopes along Koolau Mountain ridgetops from Waikane and Halawa to Mount Olympus and the summit ridges above Kuliouou and Wainmanalo, a distance of about 17 mi (27.4 km). A single mature individual was discovered in 1995 on the boundary between state land and Schofield Barracks Military Reservation, extending the distribution of this species to the Waianae Mountain Range of Oahu.

The 11 extant populations are located on private and state land and in areas on the boundary of private, state, and Federal land. These occurrences totaled about 110 individuals in 1996. Except for two populations that contained between 30-40 individuals, the remaining nine populations at Mount Olympus, Kohahuanui, Puu o Kona, Aiea-Halawa Valley summit ridge, Kaneohe-Moanalua summit, Kapakahi-Waimanalo summit ridge, Puu Kalerm, Eleao, and Moanalua all contained less than 10 individuals.

Threats

The primary threat to L. oahuensis is the noxious alien plant Koster's curse because it effectively competes for water, space, light and nutrients. Additional threats are habitat degradation and predation by feral pigs, predation by rats and slugs, and a risk of extinction from random natural events and reduced reproductive vigor due to the small number of remaining individuals.

Conservation and Recovery

Seeds of L. oahuensis have been collected by the National Botanic Garden. It is currently being propagated by the Lyon Arboretum.

Enclosures should be constructed, where practicable, around the known populations of L. oahuensis to reduce impacts from feral pigs. Subsequent control or removal of pigs from these areas will alleviate their impact on native ecosystems. Specific efforts should be made, where feasible, to immediately fence, weed, and otherwise protect the nine populations noted above that have only a few remaining individuals. A commitment should be developed for long-term stewardship and conservation of these areas once they have been enclosed. Where fencing is not deemed feasible due to topography or potential damage to sensitive summit habitat, judicious use of snaring should be used as a means of ungulate control.

Populations of L. oahuensis are seriously threatened by rat predation. A management plan to control rats should be developed and implemented. This should include the use of the currently approved diphacinone bait blocks and ultimately a more broad-scale method such as aerial dispersal of rodenticide.

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/

Senior Resident Agent Office
U.S. Fish and Wildlife Service
300 Ala Moana Boulevard, Room 7-235
P.O. Box 50223
Honolulu, Hawaii 96850-5000
Telephone: (808) 541-2681
Fax: (808) 541-3062

Reference

U.S. Fish and Wildlife Service. 28 March 1994. "Endangered and Threatened Wildlife and Plants: Endangered Status for 11 Plant Species from the Koolau Mountain Range, Island of Oahu, HI." Federal Register 59 (59): 14482-14492.