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Eugenia koolauensis

ListedMarch 28, 1994
FamilyMyrtaceae (Myrtle)
DescriptionSmall tree with branch tips covered with dense brown hair; leathery, oval or elliptic leaves; and one or two white flowers.
HabitatDry gulches and ridges in mesic forestsdominated by 'ohi'a (Metrosideras col-lina) and lama (Diospyros sandwicensis).
ThreatsCompetition from alien plants, habitat destruction by feral pigs, and limited numbers.


Nioi (Eugenia koolauensis ), a small tree in the myrtle family that reaches a height between 7 and 23 ft (2 and 7 m), has branch tips covered with dense brown hair. The leathery, oval or elliptic leaves, 0.8-2 in (2-5 cm) long and 0.4-1.3 in (1-3.3 cm) wide, are densely hairy on the lower surface and have margins that curve under the leaves. One or two flowers grow from the leaf axils on stalks 0.04-0.3 in (0.1-0.8 cm) long. The hypanthium (basal portion of the flower) is cone-shaped, about 0.1 in (0.3 cm) long, and hairy. The four sepals of unequal length that comprise the hypanthium are attached to a circular nectary dish (fleshy, nectar-producing structure). The four white petals, which are oval or elliptic and 0.2-0.3 in (0.5-0.8 cm) long, enclose numerous white stamens and are also attached to the nectary dish. The fruits are fleshy, yellow-red, oval berries, 0.3-0.8 in (0.8-2 cm) long, that usually contain one round seed. E. koolauensis, one of two species of the genus that are native to Hawaii, is distinguished from this other species in having leaves that are densely hairy on the lower surface and in having leaf margins that curve under the leaves. This species has been observed in flower from February to December in various years.


The five E. koolauensis populations exist in dry gulches and ridges in mesic forests dominated by 'ohi'a and lama at elevations of 350-1,000 ft (105-300 m). Other associated vegetation includes kolea, olopua (Nestegis sandwicensis ), hala pepe (Pleomele sp.) and alahe'e (Psydrax odoratum ).


E. koolauensis had historical occurrences on western Molokai from Maunaloa, and on Oahu from Kaipapau Valley, Hanaimoa, and Kahawainui gulches, as well as a gully southeast of Kahuku. This species is no longer believed to be extant on the island of Molokai as a consequence of the region where the first two individuals were found being converted to pineapple fields. Eight Oahu populations now remainsix in the northern Koolau Mountains and two in the southern Koolau Mountains. In the first group, one population in Papali Gulch, and two populations at Pupukea-Paumalu in Kaleleiki and Aimuu Gulch, occur on state land. Populations at Kaunala Gulch, Pahipahialua Gulch, and Oio Gulch occur on private land leased to the U. S. Army for Kahuku Training Area. The two disjunct populations in the southeastern Koolau Mountains occur at Hawaii Loa and Aina Haina. A total of fewer than 220 individuals remained in 1997. Four populations each contained between 32 and 80 individuals, but the remaining populations at Papali Gulch, Kaunala Gulch, Wailupe Gulch, and Hawaii Loa Ridge each contained fewer than 15 plants.


Habitat degradation by feral pigs, trampling by humans, close proximity to motor bike trails, and competition with the alien plants Christmasberry (Schinus terebinthifolius ), Koster's curse (Clidemia hirta ), shoebutton ardisia (Ardisia humilis ), strawberry guava (Psidium cattleianum ), and lantana (Lantana camara ) are the major threats to E. koolauensis. The limited numbers of this species and the consequent limited gene pool render it vulnerable to extinction from random natural events and through reduced reproductive vigor.

Conservation and Recovery

The Army is controlling shoebutton ardisia near the Kahuku Training Area, while also attemping to reroute mountain bike trails away from the E. koolauensis population there.

E. koolauensis has been successfully propagated at the Waimea Arboretum. The Lyon Arboretum has unsuccessfully attempted propagation.


Pacific Joint Venture
300 Ala Moana Boulevard, Room 3-122
P.O. Box 50167
Honolulu, Hawaii 96850-0056
(808) 541-2749

U.S. Fish and Wildlife Service
Regional Office, Division of Endangered Species
Eastside Federal Complex
911 N.E. 11th Ave.
Portland, Oregon 97232-4181
(503) 231-6121


U.S. Fish and Wildlife Service. 28 March 1994. "Endangered and Threatened Wildlife and Plants; Determination of Endangered or Threatened Status for 11 Plant Species from the Koolau Mountain Range, Island of Oahu, HI." Federal Register 59 (59): 14482-14492.