'Akoko

Chamaesyce herbstii

Description

Chamaesyce herbstii, a member of the spurge family (Euphorbiaceae), is a small tree ranging in height from 10-26 ft (3-8 m). The thin and leathery leaves, normally 3.1-7.7 in (8-20 cm) long and 0.7-1.5 in (1.8-3.8 cm) wide, are narrowly oblong or sometimes more lance-shaped or elliptic. The leaves are arranged in pairs on the same plane. The small, petal-less flower clusters (cyathia or compact flowering stalks with small individual flowers, the whole simulating a single flower) occur in groups of three to 15 in branched, open flowering stalks. The individual flower stalks are 0.3-0.8 in (8-20 mm) long. The hairy inflorescence bracts (specialized leaves) are broadly bell-shaped and contain five to six yellowish-green glands. The green or sometimes reddish purple-tinged, angular capsules (dry fruit that open at maturity) scarcely protrude from the bracts. This species is distinguished from others in the genus by the length of the flowering stalk and the color of the angular fruits.

C. herbstii was first described by Warren Wagner in 1988 from a specimen collected in 1969 by Derral Herbst in the Waianae Mountains of the Hawaiian island of Oahu. Other published names that Wagner considers to be synonymous with C. herbstii include C. rockii var. grandifolia, Euphorbia clusiaefolia var. grandifolia, and E. forbesii.

Habitat

C. herbstii typically grows in mesic koa-'ohi'a lowland forests, papala kepau-papala lowland forests, or diverse mesic forests at elevations of 1,750-2,300 ft (530-700 m). Associated plant taxa include the federally endangered mahoe, as well as koki'o ke'oke'o, alani, 'ala'a, and opuhe.

Distribution

Historically, C. herbstii was known from scattered populations in the northern and central Waianae Mountains on the island of Oahu. In the late 1990s, four extant populations occurred within the species' historical range. In 1997, there were four individuals at South Ekahanui Gulch, 60 at Pahole Gulch, 100 at Kapuna Gulch, and 10-12 at West Makaleha-Central Makaleha. These populations are found on private land in the Nature Conservancy of Hawaii's Honouliuli Preserve and on state land in Pahole Natural Area Reserve. The total number of plants in 1997 was estimated to be fewer than 200.

Threats

The primary threats to C. herbstii are habitat degradation and destruction by feral pigs; competition with alien plant taxa such as silk oak, huehue haole, strawberry guava, and Christmasberry; and the risk of extinction from naturally occurring events or through reduced reproductive vigor due to the small number of remaining populations.

Fire is also a potential threat to this species, which occurs in dry or mesic habitats where seasonal conditions exist for the easy spread of fire.

Conservation and Recovery

Fencing and removal of feral pigs in the Pahole drainage was completed by the State of Hawaii's Division of Forestry and Wildlife in July 1997. Weeding of strawberry guava, Christmasberry, and Koster's curse continues in the surrounding areas. Plants in the Pahole drainage have been measured and mapped, and seeds have been collected from plants outside the fence for nursery cultivation and reintroduction into the fenced areas. This species is also being propagated at the National Tropical Botanical Garden.

Contact

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

Reference

U. S. Fish and Wildlife Service. 1998. "Recovery Plan for Oahu Plants." U. S. Fish and Wildlife Service, Portland, Oreg. 207 pp.