Hilo Ischaemum

Ischaemum byrone

Description

Hilo ischaemum (Ischaemum byrone ) is a perennial grass with creeping underground stems and erect stems 16-31 in (40.6-78.7 cm) tall. The lower portion of the leaf that surrounds the stem (sheath) sometimes exhibits long hair near the base, while the upper portion is often inflated and encloses the yellow-brown flower clusters (inflorescences). The flat, hairless leaf blades are 2.8-7.9 in (7.1-20.1 cm) long and 1.2-2 in (3-5.1 in) wide, decreasing in size toward the top of the plant. Branches of the flower clusters originate at one point in twos and threes (digitate). Two-flowered spikelets (basic units of an inflorescence) are of two types: (1) one unit is sessile with a twisted bristle (awn) that is 0.9-1.0 in (2.3-2.5 cm) long; and (2) one unit is stalked with a red-brown awn that is 0.6-0.8 in (1.5-2 cm) long and twisted toward the base. The fruit is a golden oval grain (caryopsis) about 0.1 in (2.5 mm) long.

I. byrone can be distinguished from other Hawaiian grasses by its tough outer flower bracts, dissimilar basic flower units (they are awned and two-flowered), and a two-or three-branched digitate inflorescence.

Habitat

This species typically grows in coastal dry shrub-land among rocks or on basalt cliffs at elevations between sea level and 250 ft (76 m). Associated species include ko'oko'olau and naupaka kahakai.

Distribution

Historically, this species was found on Oahu at an unspecified location; on the northeastern coast of Molokai; on eastern Maui; and along the central portion of the eastern coast of the island of Hawaii.

At the turn of the twenty-first century, populations still occurred on Molokai, Maui, and Hawaii. Two populations on east Molokai are located about 2 mi (3.2 km) apart at the head of Wailau Valley and on Kikipua Point on private land. Six populations on East Maui are found along approximately 16 mi (25.7 km) of coast on private, state, and federal land. On the island of Hawaii the species is still found in two populations at Auwae and Kamoamoa on private and federal land. The total distribution of this species includes ten populations on three islands with approximately 1,200-2,200 individuals, though the total number may be in the range of 5,000 individuals.

Threats

Because this species occupies lowland habitat, it is at risk from development, alien weeds, and, in the past, feral animals. The major threats are competition from alien plants such as Henry's crabgrass and habitat change from volcanic activity.

Conservation and Recovery

The National Tropical Botanical Garden has germinated seeds and propagated the taxon. Approximately 10-15 plants were rescued from the lava flow at Lae Apuki in Hawaii Volcanoes National Park in 1992. These are presently located at the park greenhouse.

Protection of plants from ungulate (goat and deer) browsing, invasion of alien grasses, fire, and development are necessary for the recovery of this species. Efforts should be made to ensure that populations remain viable on each of the islands on which the species presently occurs.

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/

Pacific Remote Islands Ecological Services Field Office
300 Ala Moana Blvd., Room 3-122
P. O. Box 50088
Honolulu, Hawaii 96850
Telephone: (808) 541-1201
Fax: (808) 541-1216

Reference

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