Hau Kuahiwi

Hibiscadelphus woodii

Description

Hibiscadelphus woodii is a small-branched tree of the mallow family (Malvaceae) with a rounded crown that reaches a height of 8.2-16.4 ft (2.5-5 m). The leaves, on stalks 1.1-2.3 in (2.8-5.8 cm) long, have star-shaped hairs that are mostly lost as the leaves begin to mature. Awl-shaped stipules, also covered with star-shaped hairs, are found at the base of the leaf stalk. The leaf blade is ovate, 2.6-3.5 in (6.6-8.9 cm) long, and 2.6-3.3 in (6.6-8.4 cm) wide. Star-shaped hairs are scattered along the veins of the leaves. The leaf margins are irregularly and coarsely toothed with the teeth either pointed or rounded. Flowers are borne individually on stalks 0.6-0.8 in (1.5-2 cm) long with star-shaped hairs. Below each flower are four to six bracts 0.4-0.6 in (1-1.5 cm) long and 0.07-0.16 in (0.2-0.4 cm) wide. The calyx is tubular, 0.5-0.6 in (1.3-1.5 cm) long, green, shallowly lobed, and moderately hairy with star-shaped hairs. The corolla is 1.8-1.9 in (4.6-4.8 cm) long, yellow with a coppery tinge when fresh which rapidly turns purplish-maroon. The staminal column extends about 0.3 in (0.7 cm) beyond the lobes of the corolla. Fruits are not known from this species. H. woodii differs from the other known Kauai species by differences in leaf surface, involucral bract characters, and flower color.

Flowering material has been collected in March, April, and September. But no fruit set has been observed in spite of efforts to manually outcross and bag the flowers. A liquid-preserved flower contained three adult Nitidulidae beetles, probably representing an endemic species. The damage by these larvae may be responsible for the observed lack of fruit set in H. woodii. Several new species were collected on Kauai by K. Wood, M. Query, and Steve Montgomery in 1991 on the cliff walls of Kalalau Valley, including a new species in the endemic Hawaiian genus Hibiscadelphus. H. woodii was first described in 1995 by Lorence and Warren Wagner.

Habitat

H. woodii grows on cliff walls in an 'ohi'a montane mesic forest with alani, Dubautia sp. (na'ena'e), Lepidium serra ('anaunau), Lipochaeta sp. (nehe), Lysimachia sp., Chamaesyce sp. ('akoko), manono, Nototrichium sp. (kulu'i), and Myrsine sp. (kolea). The federally endangered species Stenogyne campanulata, Lobelia niihauensis, and Poa mannii (Mann's blue-grass) also occur in association with this species.

Distribution

H. woodii is known only from a single population of four individuals occurring at an elevation of 3,250-3,280 ft (990.6-999.7 m) at the site of its discovery in Kalalau Valley within the Na Pali Coast State Park on the island of Kauai.

Threats

Habitat degradation by feral goats and pigs, competition and invasion by the alien plant daisy flea-bane, nectar robbing by Japanese white-eye, and a risk of extinction from naturally occurring events and reduced reproductive vigor due to the small number of existing individuals in the only known population are the major threats to H. woodii. Japanese white-eye (Zosterops japonicus ), introduced to the island of Oahu from eastern Asia in 1930, has since spread to all of the main Hawaiian Islands. It is currently the most abundant bird in Hawaii.

Japanese white-eye has been observed piercing the corollas of H. woodii, presumably to rob nectar.

Erosion, landslides, and rock slides—destructive episodes that kill individual plants and destroy habitat—are especially dangerous threats to the only population of H. woodii.

Conservation and Recovery

Attempts by the Lyon Arboretum in 1997 to propagate this new species have been successful. The degree of damage resulting from nectar robbing by the Japanese white-eye needs to be assessed.

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