'Oha (Delissea subcordata)
|Listed||October 10, 1996|
|Description||Shrub producing six to 18 greenish white flowers, hairless anthers, and egg-shaped berries.|
|Habitat||Moderate to steep gulch slopes in mesic native or alien-dominated forests.|
|Threats||Habitat degradation and direct destruction by pigs and goats; potential impacts from military activities, including road construction and housing projects; potential predation by rats; competition with the alien plants.|
Delissea subcordata, a variety of 'oha and a member of the bellflower family, is a branched or unbranched shrub 3.5-10 ft (1-3 m) in height. The egg-shaped or oval lance-shaped leaves have heart-shaped bases and blades 4.7-12 in (12-30.5 cm) long and 2.4-6.7 in (6.1-17 cm) wide. The leaf margins have shallow, rounded to sharply pointed teeth. Occasionally the leaf margin may be irregularly cut into narrow and unequal segments with one to six triangular lobes, 0.4-0.7 in (1-1.8 cm) long, toward the leaf base. Six to 18 white or greenish-white flowers are arranged on a flowering stalk 1.6-4 in (4-10.2 cm) long. The calyx lobes are awl-shaped and 0.02-0.04 in (0.05-0.1 cm) long. The curved corolla is 1.8-2.4 in (4.5-6.1 cm) long and has a knob on the back side. The anthers are hairless, while the fruit is an egg-shaped berry. This species is distinguished from others in this endemic Hawaiian genus by the shape and size of the leaves, the length of the calyx lobes and corolla, and the hairless condition of the anthers.
D. subcordata was first collected on Oahu more than 150 years ago. It was later described and named it for its heart-shaped leaf base. All subsequently named varieties have been considered to be synonymous with D. subcordata, including D. subcordata var. kauaiensis, D. subcordata var. obtusifolia, D. subcordata var. waialaeensis, D. subcordata var. waikaneensis, and Lobelia subcordata.
D. subcordata typically grows on moderate to steep gulch slopes in mesic native or alien-dominated forests from 1,400 to 2,500 ft (426.7-762 m) elevation. Associated plant taxa include a variety of native trees such as 'ala'a, hame, kukui, 'ohi'a, papala kepau, lama, olopua, and kopiko.
Historically, D. subcordata was known from 21 scattered populations in the Waianae Mountains and eight populations in the Koolau Mountains of Oahu. A specimen collected in the 1860s and labeled as from the island of Kauai is believed to have been mislabeled. D. subcordata is now known only from the Waianae Mountains in nine populations distributed from Kawaiu Gulch in the Kealia land section in the northern Waianae Mountains to the north branch of North Palawai Gulch about 12 mi (19.3 km) to the south. This species occurs on private land at the Nature Conservancy of Hawaii's Honouliuli Preserve, on Federal land at Schofield Barracks Military Reservation and Lualualei Naval Reservation, and on state land at Pahole and Kaala Natural Area Reserves and Makua Military Reservation (a property that is leased to the Federal government). The total number of plants in the nine remaining populations was estimated to be between 70 and 80 in 1997.
D. subcordata is threatened by habitat degradation and direct destruction by pigs and goats; potential impacts from military activities, including road construction and housing development; potential predation by rats; several noxious plants: the shrub Koster's curse, dense stands of strawberry guava, Christmas berry—which grows in dense, smothering thickets, and lantana—a thicket-forming shrub; potential fire; and a risk of extinction from random natural events or through reduced reproductive vigor due to the small number of remaining individuals.
D. subcordata is directly threatened by feral goat trampling of plants and seedlings, as well as by goat-induced substrate erosion. Feral pig predation is a potential threat to D. subcordata because the plant is not known to be unpalatable to pigs and they favor plants from the bellflower family for food. D. subcordata is not known to be unpalatable to goats and grows in areas where they have been reported; direct predation is therefore a possible threat. It is possible that rats eat the fruit of D. subcordata, a plant with fleshy stems and fruit that grows in areas where rats occur.
Populations of D. subcordata that occur on land leased and owned by the U. S. Army face the threat of being damaged through military activity, either by troops in training maneuvers or by the construction, maintenance, and utilization of helicopter landing and drop-off sites. Unintentionally ignited fires from ordnance training practices on military reservations pose a potential threat to D. subcordata.
D. subcordata has populations in recreational areas, near trails, and close to roads, making it very vulnerable to human disturbance.
Conservation and Recovery
Four individuals were outplanted in a fenced enclosure in Kaluaa Gulch in Honouliuli Preserve in November 1994. Three survive, with two producing flowers and fruit; however, no recruitment has been observed. The individuals in Palawai Gulch were included in a fenced enclosure that the Nature Conservancy of Hawaii constructed in 1998. Twenty-six individuals growing in the mid-elevation Nike site in the Waianae Mountains were obtained as cuttings from the Nature Conservancy of Hawaii's Honouliuli preserve in 1997. This species is also being successfully propagated at the Lyon Arboretum, the National Tropical Botanical Garden, and the Waimea Arboretum. In addition, seeds are in storage at the National Tropical Botanical Garden.
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. 1998. "Recovery Plan for Oahu Plants." U.S. Fish and Wildlife Service, Portland, Oregon. 207 pp., plus appendices.