Delissea Rhytidosperma

views updated

Delissea rhytidosperma

No Common Name

ListedFebruary 25, 1994
FamilyCampanulaceae (Bellflower)
DescriptionBranched shrub 1.6-8.2 ft tall, with lance-shaped or elliptic toothed leaves and clusters of 5-12 greenish white or pale purple flowers.
HabitatLowland dry forests.
ThreatsDeer, goats, pigs, rats, alien plants, fire, natural disaster, human impact, low populations.


Delissea rhytidosperma is a branched shrub of the bellflower family that grows to a height between 1.6-8.2 ft (0.5 and 2.5 m). The lance-shaped or elliptic leaves with toothed margins are 3.1-7.5 in (7.9-19.1 cm) long and 0.8-2.2 in (2-5.6 cm) wide. Clusters of five to 12 flowers are borne on stalks 0.4-0.8 in (1-2 cm) long. Each flower has a stalk 0.3-0.5 in (0.8-1.3 cm) long. The greenish white corolla is 0.6-0.8 in (1.5-2 cm) long. The stamens are hairless, except for a small patch of hair at the base of the anthers. The nearly spherical dark purple fruits are 0.3-0.5 in (0.8-1.3 cm) long and contain numerous white seeds. This species differs from other plants of the genus by the shape, length, and margins of the leaves and by having hairs at the base of the anthers.


D. rhytidosperma generally grows in diverse lowland mesic forests or Acacia koa -dominated lowland dry forests, characterized by an annual rainfall of 20-80 in (50.8-203.2 cm), which falls between November and March. The terrain is a well drained, highly weathered substrate with a fine textured sub-soil rich in aluminum.


D. rhytidosperma was known from historical occurrences scattered throughout the island of Kauai. Populations ranged as far north as Wainiha and Limahuli valleys, as far east as Kapaa and Kealia, and as far south as Haupu range between the elevations of 1,000-3,000 ft (304.8-914.4 m).

Only two populations still exist. A population located on state-owned Kuria Natural Area Reserve contains six individuals. It was thought that Hurricane Iniki completely destroyed the population of 20 plants in the Haupu range in 1992, but two years later four plants and nine seedlings were observed.


Habitat degradation by mule deer, black-tailed deer, feral goats, and feral pigs is the major threat to D. rhytidosperma. Other threats are competition with alien plants such as lantana, sweet granadillal, and banana poka; predation by rats; fire; overcollecting for scientific or horticultural purposes; and landslides. With a single extant population of only six individuals, this species is threatened by stochastic extinction or reduced reproductive vigor. Hurricanes pose an additional threat.

Conservation and Recovery

D. rhytidosperma has been successfully propagated and then cultivated by Lyon Arboretum, National Tropical Botanical Garden, and Waimea Arboretum. The holdings at Lyon Arboretum in 1995 consisted of 93 plants in the tissue culture lab and one plant in the certified green house. National Tropical Botanical Garden had both seeds in short-term storage and plants growing in their garden, while Waimea Arboretum had 19 plants and 100 seedlings.


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

U.S. Fish and Wildlife Service
300 Ala Moana Blvd., Rm. 6307
P.O. Box 50167
Honolulu, Hawaii 96850
(808) 541-2749


U. S. Fish and Wildlife Service. 25 February 1994. "Endangered and Threatened Wildlife and Plant; Determination of Endangered or Threatened Status for 24 Plants from the Island of Kauai, HI." Federal Register 59 (38): 9304-9329.