Narrow-leaved Stenogyne

Stenogyne angustifolia angustifolia

Description

The narrow-leaved stenogyne is a prostrate, trailing plant. It has smooth, slender stems with forked branching. The leaves are undivided, oblong-linear or linear-lanceolate, with a hairless leathery texture, and a petiole about 0.4 in (1 cm) long. The leaf blade is typically 0.8-2.4 in (2-6 cm) long and 0.3-0.5 in (0.6-1.2 cm) wide. The calyx of the flowers is smooth, distinctly nerved, and varying from about one-half to just less than the length of the tube. The corolla (petals) is hairy or smooth, colored yellow to dull brownish-pink, about 0.8 in (2 cm) long, and has the upper lip nearly twice as long as the lower. Other varieties of this species occur on the islands of Hawaii, Maui, and Molokai, and are distinguished by differences in the morphology and arrangement of the leaves.

Habitat

The narrow-leaved stenogyne grows in relatively flat areas on ash-veneered lava, in full or nearly full sun, on very stony land characterized by shallow soil and many lava outcrops. The largest known population occurs at 5,100 ft (1,555 m) in elevation in a kipuka (a habitat island surrounded by a recent lava flow) in the Pohakuloa Training Area of the U. S. Army. The habitat is a zone of transition between native Euphorbia olowaluana forest, open Myoporum scrub-forest, and Dodonaea scrub habitat. A second population occurs southwest of Pu'u He'ewai, at about 3,450 feet (1,035 m) elevation on a very old lava substrate.

Distribution

The narrow-leaved stenogyne is a locally evolved, or endemic species that is only known from the island of Hawaii. The Hawaiian archipelago has an extremely large fraction of endemic species; about 89% of the indigenous flowering plants occur nowhere else in the world. The major population of the narrow-leaved stenogyne occurs in the saddle area formed by three volcanoes; Mauna Kea, Mauna Loa, and Hualalai.

Threats

The narrow-leaved stenogyne has suffered a decline in range and abundance because of grazing and habitat damage caused by introduced herbivorous mammals, especially feral goats (Capra hircus ) and sheep (Ovis aries ). Accidental wildfires are also a severe threat, as are non-native plants, especially fountaingrass (Pennisetum setaceum ). Trampling by military units using the Army's Pohakuloa Training Area is another problem. These are all continuing threats to the rare plant. In 1985, the major population at Mauna Kea-Mauna Loa-Hualalai was only about 100 individuals over an area of at least 100 acres (40 hectares). The population at Pu'u He'ewai was a few dozen plants in 1985.

Conservation and Recovery

Conservation of the narrow-leaved stenogyne requires that its habitat be managed to reduce the intensity of known threats. Wildfire must be avoided, and any fires that start should be quenched. The feral populations of goats and sheep should be eradicated, or protective fences erected around the stands of the endangered plant. The abundance of the most important non-native plants should be reduced. If the U. S. Army must continue to use the area for training, it is essential that the habitats of the narrow-leaved stenogyne and other threatened species be demarcated and strictly avoided. The Army has already started to do this—local regulations have been enacted governing the use of the critical kipuka habitat of the stenogyne, and notification of this exclusion zone is included in briefing sessions for new troops. The populations of the rare narrow-leaved stenogyne should be monitored, an extensive search mounted to discover whether any additional ones exist, and research undertaken into its biology and habitat needs.

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
(503) 231-6121
http://pacific.fws.gov/

U. S. Fish and Wildlife Service
Pacific Islands Ecoregion, Pacific Islands Fish and Wildlife Office
300 Ala Moana Boulevard, Room 3-122
P. O. Box 50088
Honolulu, Hawaii 96850-5000
Telephone: (808) 541-3441
Fax: (808) 541-3470

Reference

Conservation Management Institute. 13 March1996. "Stenogyne angustifolia var. angustifolia." Endangered Species Information System, Virginia Tech. (http://fwie.fw.vt.edu/WWW/esis/lists/e701005.htm) Date Accessed: July 6, 2000.