|Listed||October 10, 1996|
|Description||Annual vine up to 65 ft (20 m) long; bears white flowers.|
|Habitat||Montane wet forests.|
|Threats||Habitat damage by feral pigs; trail clearing; competition from alien plants; habitat change due to volcanic activity.|
Sicyos alba, of the gourd family (Cucurbitaceae), is an annual vine up to 65 ft (20 m) long, minutely hairy, and black-spotted. Leaves are pale, broadly heart-shaped, shallowly to deeply three-to five-lobed, 2.8-4.3 in (7-11 cm) long, and 3.5-4.7 in (9-12 cm) wide. Male and female flowers are borne in separate flower clusters on the same plant. Male flower clusters have main stalks 1-1.5 in (2.5-3.8 cm) long and individual flower stalks 0.08-0.1 in (2-2.5 mm) long. The male flowers are white, five-lobed, dotted with glands, and 0.08-0.09 in (2-2.3 mm) long. The female flower clusters have two to eight flowers, a main stalk 0.4-1.4 in (1-3.5 cm) long, and no stalks on the individual flowers. The flowers are white and four-lobed, with the lobes 0.07-0.08 in (1.8-2 mm) long. The fruit is white, fleshy, oblong, 1.1-1.3 in (2.8-3.3 cm) long, and about 0.4 in (1 cm) wide. This species can be distinguished from its nearest relative, S. cucumerinus, by its white fruit without bristles and its 10 or fewer female flowers per cluster.
First collected by the U. S. Exploring Expedition of 1840 and 1841, and considered a new but unnamed variety of S. cucumerinus in 1854, Sarx alba was named in 1978, creating Sarx as a new genus. Ian Telford returned this entity to the genus Sicyos, maintaining the species as Sicyos alba.
S. alba typically grows in 'ohi'a-and hapu'u-dominated montane wet forests, at elevations of 3,200-3,720 ft (975-1,130 m). Associated taxa include hapu'u, kawa'u, kanawao, ha'iwale, Stenogyne sp., kopiko, Perrottetia sandwicensis (olomea), olapa, ho'i'o, and Cyanea tritomantha (haha).
Historically, S. alba was found only on the island of Hawaii, from Mauna Kea, Kilauea, and the Puu Makaala area. At the end of the twentieth century, the two known populations were restricted to Puu Makaala Natural Area Reserve (NAR) and Olaa Forest Reserve, both on land in the Puna District owned by the State of Hawaii. The number of individuals fluctuates from year to year because this species is an annual. At last report, only one individual was growing at Puu Makaala NAR, but about 20 individuals were known from the Olaa population. A Sicyos collected in Hawaii Volcanoes National Park's Olaa Tract may also be this species, but the identification was not immediately confirmed.
The major threats to S. alba are habitat damage by feral pigs; trail clearing; competition from alien plants, such as banana poka, palmgrass, strawberry guava, and yellow Himalayan raspberry; habitat change due to volcanic activity; and a risk of extinction from naturally occurring events and/or reduced reproductive vigor due to the small number of existing individuals.
Conservation and Recovery
As of May 1998, the National Tropical Botanical Garden had nine seeds. Biocontrol plans to control glorybush, strawberry guava, and the yellow Himalayan raspberry will benefit this species.
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
U. S. Fish and Wildlife Service. 1998. "Big Island II: Addendum to the Recovery Plan for the Big Island Plant Cluster." U. S. Fish and Wildlife Service, Portland, Oregon, 80 pp.