'Akoko (Chamaesyce rockii)
|Listed||October 10, 1996|
|Description||A tropical shrub.|
|Habitat||Wet, native, tropical forest.|
|Threats||Habitat damage caused by introduced mammalian herbivores and disturbance by military activities, wildfire, and hurricanes.|
The 'akoko is a shrub that typically grows 1.6-6.6 ft (0.5-2 m) tall, although it can reach a height of 13 ft (4 m) in protected habitats. It has leathery leaves, ranging in shape from narrowly oblong to narrowly elliptic, and 3.0-5.5 in (8-14 cm) long and 0.8-1.4 in (2.0-3.5 cm) wide. The smooth-margined leaves are arranged in two opposite rows along the stem. The flowers occur in clusters known as cyathia, which are arranged to superficially resemble a single "flower." Each cyathium consists of groups of three to 10 branched, open to denser flowering stalks, usually 0.8-2.4 in (2-6 cm) long. The flowering stalks have bell-shaped bracts and contain five to six greenish-yellow, green, or red glands, which are nectaries that attract pollinating insects. The ripe fruit is a round, hairless capsule, 0.6-1.0 in (14-25 mm) long and colored a brilliant red (or sometimes a pink-tinged red). The ripe fruit protrudes beyond its surrounding bracts.
Flowers of the 'akoko are pollinated by native species of insects. Its seeds are scattered locally, and germinate in suitable microhabitats to establish new plants.
The 'akoko occurs naturally in lowland mesic and wet tropical forest at an elevation between 2,100 and 3,000 ft (640 and 915 m). It occurs in stands typically dominated by the trees 'ohi'a (Metrosideros polymorpha ) and uluhe (Dicranopteris linearis ).
The 'akoko is a locally evolved, or endemic species that is only known from Oahu, one of the Hawaiian Islands. The Hawaiian archipelago has an extremely large fraction of endemic species in its flora; about 89% of the indigenous flowering plants occur nowhere else. The 'akoko is known historically from scattered populations along the Koolau Mountains.
The 'akoko has declined precipitously in range and abundance because of grazing by non-native mammalian herbivores, especially pigs and to a lesser degree goats. Also critical to its decline is the replacement of its native forest habitat by communities dominated by alien plants, some of which are extreme competitors of the 'akoko, such as the strawberry guava (Psidium cattleianum ) and Koster's curse (Clidemia hirta ). Most of the surviving native habitat is restricted to the walls of steep valleys and inaccessible ridges near mountainous summits. Potential effects of military activities are also a risk to the rare plant, as are wildfire and natural disturbances such as hurricanes. Any of these disturbances could severely damage the relatively small surviving populations of the 'akoko. Eleven of the thirteen known populations still survive, and are located on private land and state land leased by the federal Department of Defense. An estimate of the population size in the late 1990s was between 200 and 400 mature plants.
Conservation and Recovery
The endangered 'akoko is a protected species, and it cannot be deliberately damaged, collected, or sold without a permit. Although the rare plant is potentially affected by military activities near its surviving habitat, it is generally protected by the steep, inaccessible nature of its critical habitat. In addition, the U.S. Army is attempting to coordinate its activities with conservation authorities to reduce or eliminate the direct effects on rare biota. This also confers protection against ongoing damage caused by pigs and goats. Conservation of the endangered 'akoko requires the reduction or elimination of mammalian herbivores from its habitat, and the designation of ecological reserves to protect its largest surviving populations.
U. S. Fish and Wildlife Service
Regional Office, Division of Endangered Species
Eastside Federal Complex
911 N. E. 11th Ave.
Portland, Oregon 97232-4181
U. S. Fish and Wildlife Service
Ecological Services Field Office
300 Ala Moana Boulevard, Room 3108
P.O. Box 5088
Honolulu, Hawaii 96850
Telephone: (808) 541-3441
Fax: (808) 541-3470
U. S. Fish and Wildlife Service. 10 October 1996. "Interior Endangered and Threatened Wildlife and Plants; Determination of Endangered Status for Twenty-five Plant Species From the Island of Oahu, Hawaii." Federal Register 61 (198): 53089-53108.