'Akoko

Euphorbia haeleeleana

Description

Euphorbia haeleeleana, a member of the spurge family (Euphorbiaceae), is a dioecious (female and male flowers on separate plants) tree that reaches a height of 10-46 ft (3.0-14.0 m). The alternate leaves are papery in texture, elliptic, and usually 4-6 in (10.2-15.2 cm) long and 2 in (5.1 cm) wide. Male trees bear many small male flowers within a cyathium (compact inflorescence with small individual flowers). The female trees have cyathia with a single female flower surrounded by numerous abortive male flowers. The trees must be cross-pollinated to produce viable seeds. The capsules, dry fruit that open at maturity, are round. This species is distinguished from others in the genus in that it is a tree, whereas most of the other species are herbs or shrubs, as well as by the large leaves with prominent veins.

Steven Montgomery and the late Wayne Gagne collected a specimen of an unidentified tree in Mahanaloa Valley on Kauai in 1970. The following year Derral Herbst described it as E. haeleeleana, naming it for another valley where the plant grows. This species has been maintained in the most recent treatment of Hawaiian members of the genus.

Habitat

E. haeleeleana is usually found in lowland mixed mesic or dry forest that is often dominated by 'ohi'a, 'ohi'a and koa, llama, or Aleurites moluccana (kukui). Typically found between 680 and 2,200 ft (207.3 and 670.6 m) in elevation, a few populations have been found at elevations up to 2,860 ft (871.7 m). Associated plant species include 'a'ali'i, Erythrina sandwicensis (wiliwili), Pleomele sp. (hala pepe), Reynoldsia sandwicensis ('ohe), and Sapindus oahuensis (aulu).

Distribution

E. haeleeleana is known both historically and currently from 15 populations located in northwestern Kauai and the Waianae Mountains of Oahu. These populations contained from 450 to 625 plants in 1997. Eleven populations occur on valley slopes and cliffs along Kauai's northwestern coast from Pohakuao to Haeleele Valley and Hipalau Valley within Waimea Canyon. All of the Kauai populations occur on state land, including Kuia Natural Area Reserve and the Na Pali Coast State Park. Four populations of 90-115 total individuals are known on Oahu from the northern Waianae Mountains. Three of these populations occur on state land leased by the U.S. Department of Defense for the Makua Military Reservation, while the fourth population occurs on privately owned land.

Threats

Habitat degradation and destruction by wild and feral black-tailed deer, goats, and pigs; predation by rats; fire; potential military activities; and competition with alien plant species seriously threaten E. haeleeleana.

Two populations of E. haeleeleana on Oahu are threatened by pigs. Goats are contributing to the decline of four populations of E. haeleeleana on Kauai. Encroaching urbanization and hunting pressure on Oahu tend to concentrate the goat populations in the dry upper slopes of the Waianae Mountains, putting one population of this plant under increasing pressure. Black-tailed deer threaten two populations of E. haeleeleana, including almost half of the known individuals on Kauai.

Cattle, deer, and goat predation is a possible threat for this plant since it is not known to be unpalatable to these animals. The largest population of E. haeleeleana on Oahu is seriously threatened by rat predation.

Military training exercises, troop ground maneuvers, and helicopter landing and drop-off activities on Oahu could trample or flatten E. haeleeleana individuals that occur on land leased or owned by the army.

Lantana poses a threat on Kauai to three populations of E. haeleeleana within Kuia Natural Area Reserve and three other populations on the island. Strawberry guava, a major invader of forests in the Waianae and Koolau Mountains of Oahu, directly threatens at least one population of E. haeleeleana there and threatens one population on Kauai. Thimbleberry poses a threat to the largest population of E. haeleeleana on Kauai.

Silk oak threatens E. haeleeleana in Hipalau Valley on Kauai and one population of the species in the Waianae Mountains of Oahu. In the same mountains, molasses grass is a serious threat to one population of E. haeleeleana.

On Oahu, unintentionally ignited fires have resulted from military training exercises in Makua Military Reservation and Schofield Barracks Military Reservation and pose a possible threat to populations of E. haeleeleana that grow in dry and mesic forest on those installations. Accidentally or maliciously set fires in residential areas near the Lualualei Naval Magazine and the Makua Military Reservation on Oahu could easily spread and pose a serious threat to most of the E. haeleeleana individuals there.

Conservation and Recovery

The U.S. Army Garrison's five-year Ecosystem Management Plan to protect endangered species, prevent range fires, and minimize soil erosion is expected to enhance conservation of the E. haeleeleana plants growing on the army's Makua Military Reservation.

Several years ago, the State Division of Forestry and Wildlife constructed a fence enclosing about half the individuals of E. haeleeleana in Mahanaloa Valley on Kauai.

E. haeleeleana has been successfully propagated at the National Tropical Botanic Gardens and Waimea Arboretum. In 1997, more than 440 seeds were in storage and 16 individuals in cultivation. An unspecified number of seeds are at Lyon Arboretum.

Exclosures should be constructed around the known populations of E. haeleeleana on state, federal, and private land to reduce impacts from ungulates. Subsequent control or removal of ungulates from these areas will alleviate their impact on native ecosystems. Additionally, specific efforts should be made to immediately fence and protect those populations that have only one or two remaining individuals, such as at Haeleele Valley and Koaie Canyon on Kauai and Keawaula gulch on Oahu.

The largest population of E. haeleeleana on Oahu is 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. Management actions to protect endangered species such as E. haeleeleana should be included in the army's plan for Makua Military Reservation, where current ordnance training exercises could unintentionally ignite fires.

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. 10 October 1996. "Determination of Endangered or Threatened Status for Fourteen Plant Taxa From the Hawaiian Islands." Federal Register 61 (198): 53108-53124.