Schiedea hookeri

No common name

Description

Schiedea hookeri is a sprawling or clumped perennial herb of the pink family (Caryophyllaceae). The stems, 1-1.6 ft (.3-.5 m) long, curve slightly upward or lie close to the ground and often produce matted clumps. The thin and opposite leaves, 1.2-3.2 in (3-8.1 cm) long and 0.2-0.6 in (0.5-1.5 cm) wide, are narrowly lance-shaped to narrowly elliptic. The apetalous, perfect flowers are borne in open branched inflorescences that are hairy, somewhat sticky, and 2-9 in (5-22.9 cm) long. The lance-shaped sepals are green to purple and 1.2-1.8 in (1.5-4.6 cm) long. The fruit is a capsule about 0.1 in (0.3 cm) long. This species is distinguished from others in this endemic Hawaiian genus by its open, hairy, and sometimes sticky inflorescence, and by the size of the capsules.

Based on field and greenhouse observations, this species is hermaphroditic (each individual has both male and female reproductive organs). Mature fruits have been observed in June and August.

A series of self-pollinations, intra-populational crosses, and crosses among populations have demonstrated that S. hookeri experiences moderately strong inbreeding. These results indicate that reductions in population size could result in expression of inbreeding depression among progeny, with deleterious consequences for the long-term persistence of this species. S. hookeri appears to be an out-crossing species. Under greenhouse conditions, flowers do not set fruit unless pollinated. In the field, the species is presumed to be pollinated by insects, although none have been observed; a related species, S. lydgatei on Molokai, is apparently pollinated by native night-flying moths.

Individuals of S. hookeri appear to be long-lived, but there isis no evidence of reproduction from seed under field conditions. Seedlings of Schiedea occurring in mesic or wet sites are apparently consumed by introduced slugs and snails, which have been observed feeding on S. membranacea, another mesic forest species that occurs on Kauai. In contrast to mesic-forest species, Schiedea occurring in dry areas produce abundant seedlings following winter rains, presumably because the drier sites have fewer alien consumers.

S. hookeri differs considerably through its range in potential for clonal growth. Plants from Kaluakauila Gulch are upright, and show little potential for clonal spread. In contrast, clonal growth has been detected for individuals at Kalnaa Gulch, where the growth form is decumbent and plants apparently root at the nodes.

S. hookeri was first described in 1854 based on a specimen collected on Oahu by Archibald Menzies of the U.S. Exploring Expedition. Earl Sherff later described S. hookeri var. acrisepala and S. hookeri var. intercedens, which are now considered synonyms of S. hookeri.

Habitat

S. hookeri is usually found in diverse mesic or dry lowland forest, often with 'ohi'a (Metrosideros collina ) or lama (Diospyros sandwicensis ) dominant, at elevations between 1,200 and 2,600 ft (365.8 and 792.5 m). One population is reported at an elevation of 2,800-2,950 ft (853.4-899 m). Associated plant species include 'a'ali'i, Artemisia australis ('ahinahina), Bidens sp. (ko'oko'olau), Carex meyenii, and Eragrostis grandis (kawelu).

Distribution

S. hookeri was known from historical occurrences the Walanae Mountains of Oahu and from a single fragmentary collection from Haleakala on Maui that may represent S. menziesii rather than S. hookeri. This species is currently known from 11 populations in Oahu's Walanae Mountains. In 1997, between 220 and 330 S. hookeri individuals were scattered on slopes and ridges from Kaluakauila Gulch to Lualualei Valley. One population of 60 plants occurred on private land in Honouliuli Preserve; three populations occurred on City and County of Honolulu land, including 40 plants on the Makaha-Waianae Kai Ridge, between 30 and more than 100 plants in Waianae Kal, and an unknown number of individuals on the Makua-Makaha Ridge; two populations occurred on state land, including about three plants in East Makaleha Gulch and about 20 plants on a ridge between Kalalula and Kanewal streams; and five populations occurred on Federal land, including three populations with a total of 55 plants on Lualualei Naval Magazine, one population of about six plants on Makua Military Reservation, and one population of five plants on Schofield Barracks Military Reservation.

Threats

The primary threats to S. hookeri are habitat degradation and destruction by feral goats and pigs and competition with alien plant species. The Kaluakauila Gulch population is also potentially threatened by fire and military activities.

Three populations of S. hookeri on Oahu are threatened by pigs. On Oahu, encroaching urbanization and hunting pressure tend to concentrate the goat populations in the dry upper slopes of the Waianae Mountains, putting two occurrences of S. hookeri there under increasing pressure.

Predation by cattle, deer, and goat predation is a possible threat.

Military training exercises, troop ground maneuvers, and helicopter landing and drop-off activities on Oahu could trample or flatten S. hookeri individuals that occur on land leased or owned by the Army.

Strawberry guava (Psidium cattleianum ), a major invader of forests in the Waianae and Koolau Mountains of Oahu, poses an immediate threat to one population of S. hookeri there. Christmasberry (Schinus terebinthifolia ), now a major component of the mesic forests of the Waianae and Koolau Mountains of Oahu, threatens six of 11 populations of this endangered species in these areas. In the Waianae Mountains of Oahu, Koster's curse (Clidemia hirta ) poses a serious threat to one of the largest populations of S. hookeri. Silk oak (Grevillea robusta ) threatens one population of this plant in the same mountains. In the Waianae Mountains on Oahu, molasses grass (Melinis minutifolia ) is a serious threat to two populations of S. hookeri. Hilo grass (Paspalum conjugatum ) and common guava (Psidium guajava ) threaten the largest population of S. hookeri in the Waianae Mountains of Oahu; here also, two populations of this species are threatened by both Maui pamakani and Hamakua pamakani (Viola sp.).

Fire poses a potential threat to populations of S. hookeri. Accidentally or maliciously set fires in residential areas near the Lualualei Naval Magazine and the Makua Military Reservation on Oahu could easily spread and pose a possible threat to several nearby populations of S. hookeri.

Conservation and Recovery

The U.S. Army Garrison's five year Ecosystem Management Plans to protect endangered species, prevent range fires, and minimize soil erosion are expected to enhance conservation of the S. hookeri plants found on the Army's Makua Military Reservation and Schofield Barracks Military Reservation.

Since 1997, the three populations on the Navy's Luaiuaiei Naval Reservation are in a designated natural management area set aside for conservation. This area is not fenced, leaving the populationsin danger of ungulate browsing. The Navy sponsors a public hunting program with bow and arrow in this area, which may help alleviate this threat.

A long-range management plan for Honouliuli Preserve has been drafted which will include actions for alien plant management, ungulate control, fire control, rare species recovery, and native habitat restoration. It is expected that these actions will benefit S. hookeri within the Preserve. S. hookeri was also outplanted in 1994 in Honouliuli Preserve within a fenced enclosure. Weeds, slugs, and rodents were also controlled. However, all S. hookeri plants within the enclosure have died. Only one naturally regenerated plant remains, outside the enclosure.

S. hookeri has been successfully propagated at the National Tropical Botanical Gardens and Waimea Arboretum. Approximately 28 individuals existed in cultivation and more than 17,000 seeds were in storage in 1997.

Management actions to protect endangered species such as S. hookeri should be implemented for Makua Military Reservation, where current ordinance training exercises could unintentionally ignite fires. A fire protection plan for endangered plants on Lualualei Naval Reservation, where current live fire training exercises are conducted and where three populations of S. hookeri occur, is also warranted.

Enhancement of these wild populations by outplantlng should begin when adequate propagated material is available, and fencing around populations and weed control are underway. Establishment of new populations within the historic range of S. hookeri should be initiated in areas free from the impacts of feral ungulates and alien plants.

Control of introduced snails and slugs is essential to protect this species, because evidence from other Schiedea species from mesic areas suggests that these alien snails and slugs consume essentially all the seeds, and probably a substantial portion of the seed crop. Methods to control their predation on seeds and seedlings of this species need to be developed and implemented.

Research on pollinators is necessary because this species is vulnerable to inbreeding depression. Declines in the native pollinator fauna might increase levels of inbreeding, resulting in the expression of inbreeding depression.

Contact

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/

Reference

U. S. Fish and Wildlife Service. 10 October 1996. "Determination of Endangered or Threatened Status for Fourteen Plant Taxa From the Hawaiian Islands." Federal Register 61 (198): 53108-53124.