'Awiwi

Centaurium sebaeoides

Description

Centaurium sebaeoides, the only species of the gentian family (Gentianaceae) native to the Hawaiian Islands, is an annual herb that reaches a height of about 2.4-8 in (6-20 cm). The leaves are clasping, rather fleshy, inversely ovate or elliptic, and 0.3-1.3 in (7.6-33 mm) long by less than 1 in (25.4 mm) wide. Flowers are stalkless and are arranged along the stems near their ends. The fused sepals are 0.3 in (7.6 mm) long and are divided into uneven lobes. The white or pale pink petals are fused into a tube up to 0.4 in (10 mm) long, with lobes up to 0.2 in (5 mm) long. The cylindrical capsules are up to 0.4 in (10 mm) long and contain numerous tiny brown seeds. This species is distinguished from C. erythraea, which is naturalized in Hawaii, by its fleshy leaves and the unbranched arrangement of the flower cluster. C. sebaeoides has been observed flowering in April. Flowering may be induced by heavy rainfall. Populations are found in dry areas, and plants are more likely to be found following heavy rains.

On the basis of a collection of specimens by Berthold Carl Seeman of what is now called C. sebaeoides,August Grisebach named a new genus of plants, Schenkia, in 1853, giving it the specific epithet of sebaeoides to indicate its resemblance to a species of Sabaea, another genus in the gentian family. The species was transferred to the genus Erythraea in 1862 by Asa Gray, then to the genus Centaurium by G. Claridge Druce in 1917.

Habitat

C. sebaeoides typically grows in volcanic or clay soils or on cliffs in arid coastal areas below 400 ft (120 m) in elevation. Associated species include Bidens sp. (kookoolau) and Lipochaeta sp. (nehe).

Distribution

C. sebaeoides was known historically from scattered localities on state and private land on the islands of Kauai, Oahu, Molokai, and Maui. This species remains on state and private land at Awaawapuhi Valley, Kalalau Beach, and Pohakuao seacliffs on Kauai; on the slopes above Halona Point and possibly at Kaena Point on Oahu; near Mokio Point and Manaeopapa on Molokai; in the Maunalei Valley on Lanai; and on West Maui.

The 10 extant populations contained no more than an estimated 580-610 plants in 1997. Kauai had three populations only 4 mi (6.4 km) apart of fewer than 100 total individuals. West Maui had one population between Waihee and Makamakaole, another population with one individual 2 mi (3.2 km) away at Makamakaole, and one population of an unknown number of individuals at Puu Koae. Oahu had one population consisting of 500 plants; Molokai had two populations with at least two plants; and Lanai had one population with approximately five plants.

Threats

The major threats to C. sebaeoides are habitat degradation by feral goats and cattle, competition from the alien plant koa haole, trampling by humans on or near trails, and uncontrolled fires. The threats are believed to be similar on Kauai, Oahu, Molokai, and West Maui.

Conservation and Recovery

Seeds from the Oahu population collected during July 1997 are now stored at the National Tropical Botanical Gardens.

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
Pacific Remote Islands Ecological Services Field Office
P. O. Box 50088
Honolulu, Hawaii 96850-5000
Telephone: (808) 541-1201
Fax: (808) 541-1216

References

Cuddihy, L. W., and C. P. Stone. 1990. Alteration of Native Hawaiian Vegetation: Effects of Humans, Their Activities and Introductions. Cooperative National Park Resources Study Unit, University of Hawaii Press, Honolulu.

Culliney, J. L. 1988. Islands in a Far Sea: Nature and Man in Hawaii. Sierra Club Books, San Francisco.

Stone, C. P., and J. M. Scott, eds. 1985. Hawai'i's Terrestrial Ecosystems: Preservation and Management. Cooperative National Park Resources Study Unit, University of Hawaii Press, Honolulu.

Wagner, W. L., D. R. Herbst, and S. H. Sohmer. 1990. Manual of the Flowering Plants of Hawai'i'. University of Hawaii Press and Bishop Museum Press, Honolulu.