Silene hawaiiensis

No Common Name

Description

Silene hawaiiensis is a sprawling shrub with slanting or climbing stems 6-16 in (15-40 cm) long originating from an enlarged root. It is covered with short, often sticky hairs. The stalkless, narrow leaves are 0.2-0.6 in (0.5-1.5 cm) long and 0.02-0.03 in (0.5-0.8 mm) wide. Flowers are arranged in elongate clusters. Each flower has a stalk 0.1-0.2 in (2.5-5 mm) long; a five-toothed purple or purple-tinged calyx 0.4-0.6 in (1-1.5 cm) long; and five petals greenish-white above and maroon below, with a stalklike base and a flat, two-lobed expanded portion about 0.2 in (5 mm) long. The fruit is a capsule about 0.3 in (8 mm) long that releases pale brown seeds 0.02-0.03 in (0.5-0.8 mm) long. This species differs from others of Silene in Hawaii by its growth habit; its covering of short, often sticky hairs; the shape of its leaves; the arrangement of its flower clusters; and the color of its petals.

This species was observed in flower during August 1964 and September 1981. No other life history information is currently available.

Habitat

This species typically grows in montane or sub-alpine dry shrublands in decomposed lava and ash, but can be found on all ages of lava and cinder substrates at elevations of 3,000-4,300 ft (910-1,310 m) and sometimes up to 8,500 ft (2,590 m). Associated species include 'a'ali'i, pukiawe, and 'ohelo.

Distribution

Historically, this species was found only on the island of Hawaii from the western slope of Mauna Kea; the summit of Hualalai; Humuula Saddle; the northern, western and northwestern slopes of Mauna Loa; and near Kilauea Crater.

Since 1975, at least 11 populations numbering more than 11,000 plants have been identified from the Hamakua district; Humuula Saddle; North Kona; the U. S. Army's Pohakuloa Training Area, including a population within the multipurpose range complex; and Hawaii Volcanoes National Park. As of June 1994, these populations were thought to be comprised of about 3,000 individuals. Surveys conducted in 1995 in Hawaii Volcanoes National Park, however, showed three populations of S. hawaiiensis consisting of more than 5,500 known plants, and surveys in the training area showed approximately 3,000 known plants.

Threats

Feral animals (goats, pigs, and sheep) are detrimental to the taxon's survival. Fragile branches and stems are easily broken or browsed almost to the base of the plant. Individuals on the lower northern slope of Mauna Loa were observed having tender new growth browsed and new leaves stripped away, thus compromising the viability of these individuals. Alien taxa, particularly Penniseturn setaceum (fountain grass), are major threats imperiling the survival of S. hawaiiensis. In certain areas where new lava is flowing from Kilauea, plants may be enveloped by molten lava rock and/or consumed by fire. Military training may jeopardize plants on Pohakuloa Training Area. This taxon may be increasingly vulnerable where human habitation is expanding or development is occurring.

Conservation and Recovery

In 1992-93, seeds were germinated by staff at Colorado State University. Seedlings were grown in the greenhouse. In 1993, seeds were germinated at Pohakuloa Training Area and about 50 seedlings were outplanted on Puu Kapele. A population of more than 20 individuals survived and produced flowers and fruits. The taxon is growing with Eragrostis defiexa in ash on the northwestern slope of the puu, at an elevation of about 5,805 ft (1,770 m).

Recent discoveries of several large populations indicate that this plant is not as rare as once thought. Populations should be monitored to ensure that numbers are being maintained. After habitat on which at least five of the larger populations occur is managed to control threats from feral animals, alien taxa, and military training, delisting of this species can be considered.

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

U. S. Fish and Wildlife Service Pacific Remote Islands Ecological Services Field Office
300 Ala Moana Blvd., Room 3-122
P.O. Box 50088
Honolulu, Hawaii 96850-5000
Telephone: (808) 541-1201
Fax: (808) 541-1216
http://www.r1.fws.gov/pacific/

Reference

U. S. Fish and Wildlife Service. 4 March 1994. "Determination of Endangered or Threatened Status for 21 Plants from the Island of Hawaii, State of Hawaii." Federal Register 59 (43): 10305-10325.