Schiedea membranacea

No Common Name

Description

Schiedea membranacea is a perennial herb of the pink family. Its unbranched, fleshy stems rise upward from near the base and are somewhat sprawling—1.6-3.3 ft (0.5-1.5 m) long with internodes 2.4-4.7 in (6.1-11.9 cm) long. During dry seasons, the plant dies back to a woody, short stem at or beneath the ground surface. The oppositely arranged leaves, 5-8 in (12.7-20.3 cm) long and 2-3.2 in (5.1-8.1 cm) wide, are broadly elliptic to egg-shaped, generally thin, have five to seven longitudinal veins, and are sparsely covered with short, fine hairs. The perfect flowers have no petals, are numerous, and occur in large branched clusters. The inflorescences are about 10-10.6 in (25.4-26.9 cm) long. The purple, lance-shaped sepals are about 0.08 in (2 mm) long and have thin, dry, membranous margins. The flowers contain three to five styles and probably ten stamens. The capsular fruits, 0.1-0.12 in (2.5-3 mm) in length, are purple at the apex. This species differs from others of the genus that grow on Kauai by having five-to seven-nerved leaves and an herbaceous habit.

S. membranacea appears to be a long-lived perennial. Plants marked in Mahanaloa Gulch in 1987 were alive in 1997, after Hurricane Iniki. There was no evidence of recruitment in the population, despite the production of abundant seed during all years of observation (1987, 1994-97). Introduced snails have been observed feeding on flowers and developing seed capsules, and garlic snails are common near the plants. It seems very likely that introduced mollusks are responsible for the failure of recruitment.

Under greenhouse conditions, this species, as well as other Schiedea species, is extremely sensitive to slugs and snails, further suggesting that the introduction of these alien species has had detrimental effects on Schiedea species in natural conditions.

Research on pollinators is necessary because of the possibility that declines in native pollinator fauna might increase levels of inbreeding and, in turn, result in the expression of inbreeding depression.

Robert Hobdy collected a specimen of S. membranacea on Kauai in 1969. The species was described and named three years later. The specific epithet refers to the membranous texture of the leaves.

Habitat

S. membranacea is typically found between 1,700-3,800-ft (518.2-1,158.2 m) elevations on cliffs and cliff bases in a wide variety of mesic to wet habitats. The vegetation ranges from open to closed lowland to montane shrubland to forest communities either with a variety of canopy and understory species or dominated by kukui, mamaki, or 'ohi'a.

Distribution

S. membranacea is known from six current populations on the western side of the island of Kauai: Mahanaloa-Kuia Valley, Nualolo, and Paaiki, Kalalau, Wainiha, and Waialae valleys on state (including Kuia Natural Area Reserve and Na Pali Coast State Park) and privately owned land. This species is not known to have occurred at any other locations. Although the number of plants of this species remaining in Paaiki Valley is not known, about 200-250 individuals are known in the other five populations.

Threats

The populations at Kalalau Valley, Nualolo, and Waialae Valley are threatened by feral pigs, while the populations at Kalalau Valley, Mahanaloa-Kuia Valley, and Waialae Valley are threatened by goats. Mule deer threaten the Mahanaloa-Kuia Valley and Nualolo populations.

Maui pamakani, a naturalized noxious weed that lives in dry areas to wet forests on Kauai, and Hamakua pamakani, naturalized in disturbed dry to mesic areas and wet forests on Kauai, threaten the Kalalau Valley population. Lantana, a thicket-forming shrub capable of dominating native habitat, threatens some populations as does banana poka, a woody vine, and prickly Florida blackberry. Strawberry guava and thimbleberry pose a direct threat to the Mahanaloa-Kuia Valley population.

Erosion, landslides, and rock slides—natural events that can kill individual plants and destroy habitat—are especially dangerous threats to the largest population of S. membranacea.

Conservation and Recovery

This species has been successfully propagated from seed. There were 20 S. membranacea plants in cultivation in 1997 and more than 9,000 seeds in storage.

Surveys in Paaiki Valley should be conducted to determine how many individuals still exist in this area.

Because of the threat from hoofed mammals, enclosures should be constructed around the existing populations. To insure that the enclosures are not threatened by landslides, the existing six populations should be evaluated and ranked according to landslide threat prior to construction of enclosures. Without this protection, this species will continue to decline due to degradation of habitat by feral pigs. Once enclosed, those areas should undergo management that targets the reduction and removal of daisy flea-bane, lantana, and prickly Florida blackberry.

Enclosures will protect adult plants from ungulate damage, but they will neither reverse the low germination observed in Mahanaloa Gulch nor the presumed eventual decline of this species due to lack of recruitment. Therefore, experiments should be undertaken to determine if snails and slugs are the major cause of recruitment failure. Once this determination has been made, appropriate recommendations can be made for long-term protection.

Pollinators appear to be critical to the high out-crossing rate of this species; if they were to decline, very high levels of inbreeding depression in S. membranacea would be expressed. Any long-range recovery plan must take into account this possibility. Without any knowledge of the pollinators, it will be impossible to implement plans ensuring survival of this species. Observations should be carried out during the day and night, since S. lydgatei is pollinated by night-flying moths, and it seems likely that the same or similar insects pollinate S. membranacea. Once pollinators have been identified, aspects of the management plan may be modified to ensure survival of the pollinating species as well.

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. 1988. "Kauai II: Addendum to the Recovery Plan for the Kauai Plant Cluster." U. S. Fish and Wildlife Service, Portland, Oregon. 84+ pp.