No Common Name
|Listed||May 13, 1992|
|Description||Climbing shrub with paired, inversely lanceolate leaves and clusters of flowers in the leaf axils.|
|Habitat||Steep slopes of gulches in mesic koa forests.|
|Threats||Invasive alien plants, feral pigs.|
Chamaesyce halemanui is a climbing shrub of the spurge family that grows to a height of 3.3-13 ft (1-4 m). The elliptical to oblanceolate leaves, 1.5-5 in 3.8-12.7 cm) long, are arranged in pairs along the stem with each succeeding pair at right angles to the previous one (decussate). Dense flower clusters, as well as occasional solitary flowers, are borne on short stems arising from the leaf axils. The fruits are green capsules that enclose gray to brown seeds. In the past this species has also been known as Euphorbia remyi var. wilkesii, E. remyi var. leptopoda, and E. remyi var. molesta.
C. halemanui is one of a large number of species endemic to the Kokee area, a habitat in the northwestern part of the Hawaiian island of Kauai that is roughly encompassed by the 8-sq-mi (21-sq-km) Kokee State Park. C. halemanui is found on the steep slopes of gulches in the moist koa (Acacia koa ) forests of Kokee at elevations of 2,160-3,600 ft (660-1,100m). Five other plant species endemic to the Kokee region are federally listed as endangered: Dubautia latifolia, Hawaiian bluegrass (Poa sandvicensis ), P. siphonoglossa, Stenogyne campanulata, and Xylosma crenatum.
C. halemanui, first collected on Kauai in 1840, was found historically at seven areas on the island: Kauhao and Makaha Valleys in the Na Pali-Kona Forest Reserve; Mahanaloa Valley in Kuia Natural Area Reserve; the Halemanu drainage, near Waipoo Falls and near Kokee Ranger Station in Kokee State Park; and Olokele Canyon on privately owned land.
In the late 1990s, the Kauhao Ridge, Makaha, Waialee Ridge, and Halemanu drainage occurrences of C. halemanui had respective populations of 15, 50-100, six, and 25-30 individuals. These 96-151 extant plants all grew on state land.
The most immediate threat to C. halemanui is vegetative competition from alien plant species. The Halemanu population in Kokee State Park is threatened by St. Augustine grass, which prevents the establishment of seedlings; the two populations in the Na Pali-Kona Forest Reserve are threatened by lantana and strawberry guava. In the Kuia Natural Area Reserve, illegal marijuana cultivation is a threat to native species, including C. halemanui. Not only is native flora destroyed in clearing land for cultivation, but alien species are introduced into the area from soil and other material brought to the site.
In addition, feral pigs threaten to degrade native plant habitat in the forest reserve. Pigs have inhabited the forests of Kauai for more than a century, and have proven extremely destructive to native plant species. Their rooting destroys vegetative cover, allowing the invasion of alien plant species, and their feces add nutrients to poor soils that would otherwise favor native species.
Various human activities have promoted the spread of feral pigs on Kauai. In forested areas the pigs use paths made by other animals or humans to move into new areas. The logging of the Kokee area in the nineteenth century created a multitude of small trails that led to the southern coast; in the 1920s construction of the Kokee/ Kekaha ditch and water diversion system, designed to irrigate lowland sugar cane fields, cut more roads into the area. Plum trees were planted in Kokee State Park in the 1930s, providing a food source that attracted feral pigs.
In addition to these known threats, the low number of existing C. halemanui plants puts the species at risk of extinction through unpredictable human or natural events.
Conservation and Recovery
C. halemanui has been successfully propagated by the National Tropical Botanical Garden, and the Division of Forestry and Wildlife has fenced the Makaha Ridge population.
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
U. S. Fish and Wildlife Service
Pacific Remote Islands Ecological Services Field Office
300 Ala Moana Blvd., Room 3-122
P.O. Box 50088
Honolulu, Hawaii 96850-5000
Telephone: (808) 541-1201
Fax: (808) 541-1216
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.
Macdonald, G. A., A. T. Abbott, and F. L. Peterson.1983. Volcanoes in the Sea. 2nd ed. University of Hawaii Press, Honolulu.
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.
U. S. Fish and Wildlife Service. 13 May 1992, "Determination of Endangered Status for Six Plants from the Kokee Region, Island of Kauai, Hawaii." Federal Register 57 (93): 20580-20587.
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.