Viola oahuensis

No Common Name

Description

Viola oahuensis is an erect, unbranched subshrub of the violet family (Violaceae) that usually reaches a height of 2.4-16 in (6-40 cm). The papery-textured leaves are usually 1.2-4.7 in (3-12 cm) long, 1-2.3 in (2.5-6 cm) wide, and elliptic-egg-shaped to elliptic. The leaf stalks are typically 0.2-0.4 in (0.5-1 cm) long. The narrowly triangular stipules are usually 0.4 to 0.6 in (1-1.5 cm) long, 0.1-0.2 in (0.25-0.5 cm) wide, and have fringed edges. One to two flowers with pale yellow petals are borne on stalks that are typically 1-2.4 in (2.5-6 cm) long. Upper petals are 0.3-0.5 in (0.7-1.3 cm) long; lateral petals are 0.4-0.5 in (1-1.3 cm) long; lower petals are 0.5-0.6 in (1.3-1.5 cm) long. The capsules are 0.4-0.6 in (1-1.5 cm) long. This species is distinguished from other Hawaiian members of the genus by the stipule characters, the length of the leaf stalks, and the length and papery texture of the leaves.

V. oahuensis was described in 1909 from a specimen collected in the Koolau Mountains. This species has been maintained in the most recent treatment of Hawaiian members of this genus.

Habitat

V. oahuensis is generally found on exposed, windswept ridges of moderate to steep slope in wet 'ohi'a-uluhe shrublands from 2,300-2,800 ft (701-853 m) elevation. This species typically grows among wind-stunted na'ena'e pua melemele, 'uki, Sadleria sp. ('ama'u), 'ohi'a ha, and Vaccinium sp. ('ohelo).

Distribution

V. oahuensis was known historically on Oahu from 17 populations scattered over about a 23 mi (37 km) distance from Puu Kainapuaa to Palolo in the Koolau Mountains. The eight extant populations are now found from the Kawainui-Koloa summit divide to the Waimalu-Koolaupoko divide over a 12 mi (19 km) distance. These populations are found on the Department of Defense land; state land, including land leased by the Department of Defense for Kawailoa Training Area; City and County of Honolulu land; and private land, including land leased by the Department of Defense for Kawailoa Training Area. Farther to the south, at the summit of Moanalua, a single plant, last seen alive in 1991, has since died. The extant populations contained fewer than 180 individuals in 1997. The two populations at the Koolau summit between Manana and Kipapa and Waimalu-Koolaupoko divide contained 50-100 individuals; however, the two populations along the Peahinaia Trail, four populations at the Kawanui-Koloa summit divide, one population at Kahana-S. Kaukonahua, and three populations at the Koolau summit between Waimano and Kipapa each harbored fewer than ten individuals.

Threats

The primary threats to V. oahuensis are habitat degradation and destruction by feral pigs; potential impacts from military activities; competition with Koster's curse, strawberry guava, Hilo grass, and Glenwood grass; and risk of extinction from naturally occurring events or through reduced reproductive vigor due to the small number of populations. Populations of V. oahuensis 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.

Conservation and Recovery

Viola oahuensis is being propagated at the National Tropical Botanical Garden.

Contact

U. S. Fish and Wildlife Service
Regional Office, Division of Endangered Species
Eastside Federal Building
911 N. E. 11th Ave.
Portland, Oregon 97232-4181
Telephone: (503) 231-6121
http://pacific.fws.gov/

Reference

U.S. Fish and Wildlife Service. 1998. "Recovery Plan for Oahu Plants." U.S. Fish and Wildlife Service, Portland, Oregon.