|Listed||March 4, 1994|
|Description||Tree with opposite-stalked, oval, thin, pinnately veined, toothless leaves and 10-12 greenish-yellow or white bisexual flowers.|
|Habitat||Lama-dominated lowland dry and mesic forests, often on lava.|
|Threats||Competition from alien plants; habitat destruction by feral pigs; fire; insects; military exercises; and limited regeneration.|
Kauila (Colubrina oppositifolia ) is a tree 16-43 ft (4.9-13.1 m) tall, with opposite-stalked, oval, thin, pinnately veined, toothless leaves that have glands on the lower surface. Leaves measure 2.4-4.7 in (6.1-11.9 cm) in length and 1.2-2.8 in (3-7.1 cm) in width in mature plants and are larger in seedlings. Ten to twelve bisexual flowers are clustered at the end of a main stalk 0.1-0.3 in (2.5-7.6 mm) long; each flower has a stalk about 0.07-0.1 in (2-2.5 mm) long that elongates in fruit. The five triangular sepals measure about 0.06-0.08 in (1.5-2 mm) long, and the five greenish-yellow or white petals are about 0.06 in (1.5 mm) long. The somewhat spherical fruit—0.3-0.4 in (7.6-10.2 mm) in length—is similar to a capsule and opens explosively when mature. This species can be distinguished from the one other species in the genus in Hawaii by its growth habit and by the arrangement, texture, venation, and margins of its leaves. C. oppositifolia has been observed to fruit and flower in September and June and also flowers in December and January.
This species typically grows in lama-dominated lowland dry and mesic forests, often on lava, at elevations of 800-3,000 ft (244-914 m). Associated species include alahe'e and 'ohe.
Historically, C. oppositifolia was found on the island of Oahu in the central and southern Waianae Mountains and on the island of Hawaii in the following areas: the Kohala Mountains; the northern slope of Hualalai; and the western, southwestern, and southern slopes of Mauna Loa.
By the mid-1990s the species was known on Oahu in eastern Makaleha Valley, Mokuleia Forest Reserve, and Makua Valley; on Mt. Kaala; and near Honoulluli Contour Trail on private, state, and federally managed land. On the island of Hawaii the species occurred along the Mamalahoa Highway on the northern slope of Hualalai, as well as in Kapua and Puueo on the southernmost portion of the island.
The six extant populations on Oahu, which extend over a distance of about 9 by 4 mi (14.5 by 6.4 km), contain approximately 94 individuals. On the island of Hawaii there are seven extant populations that extend over a distance of about 16 by 4 mi (25.7 by 6.4 km). These populations contain about 185-205 known individuals.
Major concerns are habitat destruction by feral pigs and the introduction of aggressive alien plant taxa, particularly lantana, fountain grass, and Christmasberry. Furthermore, the introduction of the black twig borer could lead to the demise of C. oppositifolia. Xylosandrus compactus is actively attacking trunks and twigs of the trees at Puu Waawaa, and this population—the largest known for the species—is declining. The insects reduce the individuals' vigor, which eventually leads to the death of the plant. Chinese rose beetles (Adoretus sinicus ) may also be a threat to the Maui population.
Decimation by fire is a concern because population numbers are small and distributions are limited to concentrated areas, particularly on the dry, leeward sides of islands. Disturbance by military and unauthorized personnel may compromise habitats and jeopardize the survivability of individuals.
Conservation and Recovery
The National Tropical Botanical Garden has germinated seeds and propagated the taxon. Lyon Arboretum has attempted to clone C. oppositifolia from buds and immature seeds with no success. The Hawaii Division of Forestry and Wildlife is actively propagating the taxon from seed and has out-planted approximately 64 plants into several enclosures on Puu Waawaa.
Protecting habitat from ungulates and controlling aggressive alien plant taxa such as lantana, fountain grass, and Christmasberry are necessary for recovery of the species, as is reducing the threat of fire. Control of the black twig borer, and research necessary to accomplish this, should be undertaken to stem the species' demise. Steps should be taken to ensure that populations remain viable on each of the islands on which the species presently occurs.
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
Pacific Remote Islands Ecological Services Field
300 Ala Moana Blvd., Room 3-122
P.O. Box 50088
Honolulu, Hawaii 96850
Telephone: (808) 541-1201
Fax: (808) 541-1216
U.S. Fish and Wildlife Service. 1996. "Big Island Plant Cluster Recovery Plan." U.S. Fish and Wildlife Service, Portland, Oregon. 202 + pp.