Mariscus pennatiformis

No Common Name

Description

Mariscus pennatiformis, a member of the sedge family, is a perennial plant with a woody root system covered with brown scales. The stout, smooth, three-angled stems are 1.3-4 ft (0.4-1.2 m) long, slightly concave, and 0.1-0.3 in (2.5-7.6 mm) in diameter in the lower part. The three to five linear, somewhat leathery, leaves are 0.3-0.7 in (7.6-17.8 mm) wide and at least as long as the stem. Each flower cluster—umbrella-shaped and moderately dense—is 1.5-6 in (3.8-15.2 cm) long and 2-10 in (5.1-25.4 cm) wide. About 5-18 spikes, comprised of numerous spikelets, form each cluster. Each spikelet, measuring about 0.3-0.6 in (7.6-15.2 mm) in length, is yellowish-brown or grayish-brown and has 8-25 densely arranged flowers. The spreading and tightly overlapping glumes (bracts beneath each flower) are almost twice as long as they are wide. The lowest glume does not overlap the base of the uppermost glume.

This species differs from other members of the genus by its three-sided, slightly concave, smooth stems; the length and number of spikelets; the leaf width; and the length and diameter of stems. M. pennatiformis ssp. pennatiformis is distinguished from M. pennatiformis ssp. bryanii by its larger and more numerous spikelets, larger achenes (dry, one-seeded fruits), and more overlapping and yellower glumes.

The name Cyperus pennatiformis was coined by Georg Kukenthal in 1932 from a specimen collected from Hana on Maui. He also described var. bryanii, a variety of this species collected from the northwestern Hawaiian island of Laysan. Tetsuo Koyama later recombined the species under the genus Mariscus, while maintaining the two subspecific designations as subspecies.

Habitat

M. pennatiformis ssp. pennatiformis occurs at open sites in mesic forests and low elevation grasslands from sea level to 3,940 ft (1,201 m) in elevation. M. pennatiformis ssp. bryanii occurs on sandy substrate at an elevation of 16 ft (5 m). Associated species include Cyperus laevigatus (makaloa), Eragrostis variabilis (kawelu), and Ipomoea sp.

Distribution

M. pennatiformis ssp. pennatiformis occurred in six historical populations on four islands. The species came from Halemanu in Kokee State Park on Kauai; from a ridge above Makaha Valley in the Waianae Mountains of Oahu; from Keanae Valley, Hana, and Nahiku on East Maui; and from an unspecified location on the island of Hawaii. Only one population has been seen since the 1920s, when an unknown number of plants was observed sometime in the 1970s in Keanae Valley.

M. pennatiformis ssp. bryanii is known only from Laysan Island in the Hawaiian Islands National Wildlife Refuge. This subspecies was found until the early 1990s on the southeastern end of the central lagoon, as well as on the western and northeastern sides of the island on sandy substrate at an elevation of 16 ft (5 m). The population has fluctuated from as many as 200 to as few as one individual throughout the 1990s. Only one population of about 200 individuals at the southeastern end of the lagoon remained on Laysan Island in 1997.

Threats

The initial decline of M. pennatiformis ssp. bryanii was probably caused by the release of rabbits on Laysan Island and their subsequent destruction of almost all of the island's vegetation. Causes of the recent decline and current threats to M. pennatiformis ssp. bryanii are unclear, but seed predation by the endangered Laysan finch is a probable threat, since the finches have been observed feeding on the seeds; destruction of the remaining individuals by the burrowing activities of nesting seabirds is also a possible threat. The native beach morning glory is yet another possible threat, since it periodically grows over the Mariscus individuals.

Threats to M. pennatiformis ssp. pennatiformis are unknown; it was last seen in the wild in the 1970s. Threats to historical locations included grazing and habitat degradation caused by ungulates; competition for light, water, space, and nutrients from a variety of alien plant species; and fire.

The small number of individuals of M. pennatiformis make the two subspecies covered by this name extremely vulnerable to either quick extinction through natural events or more protracted extinction through reduced reproductive vigor.

Conservation and Recovery

There is an unconfirmed report that M. pennatiformis ssp. pennatiformis existed in cultivation at the Maui Zoological and Botanical Gardens. Since the gardens were closed to the public in early 1997, the current status of this subspecies in the gardens is unknown. The cultivated plants were originally from Nahiku, East Maui.

Seeds from a single flowering individual of M. pennatiformis ssp. bryanii were collected by U.S. Fish and Wildlife Service (FWS) personnel in October 1994 and propagated at the University of Hawaii's Lyon Arboretum and at Waimea Arboretum. As of 1997, 219 individuals were in cultivation at Lyon and Waimea arboretums. Reintroduction of cultivated individuals has been considered, but a method to keep the plants healthy during the long sea voyage has not yet been developed.

In 1995 FWS personnel on Laysan Island began an ongoing monitoring and protection program for the current wild individuals, which includes the bagging of the seed heads to prevent Laysan finch predation. Mature seed has also been spread in suitable areas. Control of beach morning glory is conducted when it begins to cover the Mariscus plants, and a Laysan albatross (Diomedea immutabilis ) chick was relocated when it began to tear pieces from a Mariscus individual. Most of the individuals have been enclosed by a small fence erected to prevent albatrosses from trampling the plants.

Plants must be protected from Laysan finch predation and seabird roosting and nesting. Bagging of seed heads has been partially successful, but some seed heads have suffered molding as a result. Other methods of protecting the plants should be devised that will keep out Laysan finches and discourage roosting and/or nesting of seabirds in the immediate area.

Protection from burrowing seabirds should also be implemented, possibly through sturdy wire mesh covering the ground for 10 ft (3 m) around each plant.

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/

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. 10 November 1994. "Endangered Status for 12 Plants from the Hawaiian Islands." Federal Register 59 (217): 56333-56351.