Schiedea haleakalensis

No Common Name

Description

Schiedea haleakalensis is a smooth, hairless shrub in the pink family (Carophyllaceae) that grows to a height of 12-24 in (30-60 cm). Its climbing herbaceous branches have slightly fleshy, needlelike, and single-nerved leaves that occur in pairs on the stem.

The clustered flowers, no more than 0.2 in (0.5 cm) in length, are located at the ends of the branches. These petal-less flowers have five green and oval sepals, five nectaries, and 10 stamens. The capsules contain grayish to reddish-brown seeds. This species differs from others in the genus on East Maui by its crowded, hairless inflorescence composed of bisexual flowers.

S. haleakalensis bears female and both-sexed flowers on separate plants; this gynodioecious condition means the species probably requires cross-pollination by small insects for seed set. Small flies and moths have been noted visiting the flowers at both known populations. These insects are not noted for being able to fly more than relatively short distances. Fruits and seeds have been observed in August and September. There are no obvious dispersal devices for seeds other than gravity and water-borne movement.

Habitat

The current habitat of S. haleakalensis is in rock cracks on sheer cliffs at elevations of 5,900-8,000 ft (1,800-2,440 m) adjacent to barren lava and predominantly native subalpine shrublands and grasslands. The substrate is cinder, weathered volcanic ash, or bare lava with little or no soil development. Associated native species include Artemisia mauiensis, Bidens micrantha, Dubautia mensiezii, Styphelia tameiameiae, Vaccinium reticulatum, and Viola chamissoniana. The annual precipitation is 15-40 in (38-102 cm). Periodic frost and occasional snow cover occur on the upper limits of this habitat.

Distribution

Due to the lack of early collections, the historical range of S. haleakalensis is unknown. This species is currently known from three populations in Haleakala National Park on East Maui: Holua at 7,200-8,000 ft (2,200-2,440 m) in elevation, on north-facing cliffs of Haleakala Peak at 7,500-7,700 ft (2,290-2,350 m) in elevation, and in upper western Kaupo Gap at 5,900-6,100 ft (1,800-1,860 m) in elevation. The three populations, which together extend over a total area of about 27 acres (11 hectares), are estimated to contain a total of 100-200 individuals; because of the inaccessibility of the habitat, however, a complete survey is lacking. S. haleakalensis has survived only on precipitous cliff faces inaccessible to goats. In spite of the removal of goats in the late 1980s from habitat of this species in Haleakala National Park, no establishment by seedlings has ever been observed. Slugs may be completely devouring the seedlings.

Threats

The very small remaining number of individuals of S. haleakalensis and the limited and scattered distribution of the species are threats, since a single natural or human-caused environmental disturbance could be catastrophic to all or a significant part of the populations. The limited gene pool may also depress reproductive vigor, while three very small, scattered populations may not receive adequate cross-pollination.

There is evidence that alien slugs in the Waianae Mountains of Oahu eat Schiedea seedlings. The invasive garden slug Milax gagates has been observed to partially defoliate larger, established S. haleakalensis plants in the western Kaupo population. This slug is now widespread on upper Haleakala Volcano in a variety of high-elevation sites, arid to wet, and has been observed feeding on such rare native plants as the greensword. An Argentine ant has invaded the habitat and is capable of reducing or eliminating native pollinators wherever it invades on Haleakala Volcano. As of 1994, the invasion had descended from Kalahaku on the rim of Haleakala Crater to the crater floor very near the Holua population of S. haleakalensis.

Although feral goats have been removed from Haleakala National Park by a program of active management and are no longer an immediate threat to native plant species within the park, the potential for the ingress and reestablishment of goats exists. Maintenance of a goat-free situation requires continuation of an active management program, which requires substantial sustained commitment by Haleakala National Park and funding for fence maintenance and goat removal.

The possibility of fire is a threat to the existence of S. haleakalensis; a single fire could affect a significant portion of one or all of the populations of this species.

Conservation and Recovery

Exclusion of feral goats from Haleakala National Park required a major effort by the National Park Service. Without that important step, no serious possibility would exist for the recovery of the species. Three seeds of S. haleakalensis were collected in July 1991, and three individuals of this species were growing in a greenhouse in Irvine, California, by the following January. Progeny were also obtained later from seeds from these three individuals, and it appears that the species is very easy to grow.

One of the benefits of goat control in the national park is that the increase of biomass—a progressive condition that will continue over many decades of growth unhampered by goats—may increase the availability of moister, semishaded microsites for germination and increase the numbers of generalist native insects, such as flies, moths, and bees, which can act as pollinators for this pollinator-dependent species.

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. 15 May 1992. "De-termination of Endangered or Threatened Status for 15 Plants from the Island of Maui, Hawaii." Federal Register. 57 (95): 20772-20787.