Na'ena'e (Dubautia pauciflorula)
|Listed||September 20, 1991|
|Description||Tall shrub with leaves near the ends of branches and clusters of yellow flower heads.|
|Habitat||Ridges and stream banks.|
|Threats||Low numbers, alien plant species.|
Dubautia pauciflorula (Na'ena'e) is a somewhat sprawling shrub or erect small tree in the aster family that can reach 10 ft (3 m) in height. Its narrowly lance-shaped or elliptic leaves, broadest above their middles, are 3-8 in (7.5-24 cm) long, 0.5-1.3 in (12.5-32.5 mm) wide and clustered toward the ends of the stems. There are 50-500 flower heads in a purplish, open, and pyramidal inflorescence 3-12 in (7.5-30 cm) long and 2-12 in (5-30 cm) wide. Each head comprises 2-4 yellow florets 0.1-0.15 in (2.5-3.75 mm) long. The fruits are small, dry seeds (achenes) about 0.1 in (2.5 mm) long, with a crown of slender bristles (pappus) 0.1-0.15 in (2.5-3.75 mm) long. Flowering material was collected in August, September, and November and fruiting material in November. The tiny heads with two to four flowers distinguish this species from its relatives.
Few details are known about the life history of any Dubautia species under natural conditions. Certain species produce viable seed when self-pollinated (are self-fertile), although others fail to do so (are self-infertile). Low pollinator numbers resulting in reduced cross-pollination and consequent low numbers of viable seeds could explain the small population sizes. Because of their structure and small size, flowers of D. pauciflorula are presumably pollinated by small generalist insects, although field observations are lacking. The bristle-like pappus crowning the fruit probably represents an adaptation for wind dispersal. Very little is known about the life cycle of this species, including growth rates, longevity of the plants, and number of years the plants remain reproductive.
The original Forbes and Lydgate collections of D. pauciflorula. were made in 1909 and 1911 in the Wahiawa Mountains on a ridge just above a tributary of the Wahiawa Stream. This species was recollected in 1979 in the Wahiawa Mountains from an east-facing ridge of 2,300 ft (690 m) elevation and 10° slope that was 98 ft (29 m) from the Hanapepe fork of Wahiawa Stream. This same population of about 30 plants was known in 1991.
Forty-seven individuals of this species, 25 adults and 22 juveniles, are known from four localities in the Wahiawa Drainage. Thirty-nine of the plants were confined to the original type locality in a small valley near a stream, where almost half the population consisted of juveniles despite heavy infestation by strawberry guava. The three other sites were along streams where guava invasion is also a serious problem. All individuals were sterile during the survey period. Nearly equal numbers of adults and juveniles indicate regeneration is occurring, albeit slowly.
The D. pauciflorula has declined because of habitat loss, competition and habitat change caused by invasive alien plants (especially the strawberry guava, Psidium cattleianum ), feeding by introduced mammalian herbivores, and perhaps the decline of its native pollinator species. The small number of surviving plants is still affected by these influences, as well as the inherent risks of extinction associated with a tiny population size occurring in only a single critical habitat.
Conservation and Recovery
Hawaii Plant Conservation Center staff collected 166 seeds of D. pauciflorula in 1991 for subsequent propagation, although no seeds have germinated. Cuttings of D. pauciflorula and many other species of Dubautia were successfully rooted in perlite and grown in a growth chamber at the University of Hawaii between 1979 and 1992. Some species, including D. pauciflorula, actually flowered. All plants of these Dubautia species died after outplanting on Oahu in the Waimea Arboretum at Haleiwa and the Lyon Arboretum at Honolulu. No natural site conservation efforts have been attempted to date.
U.S. Fish and Wildlife Service
Office of the Regional Director
Eastside Federal Complex
911 N.E 11th Avenue
Portland, Oregon 97232-4181
Telephone: (503) 231-6118
Fax: (503) 321-2122
U.S. Fish and Wildlife Service
Senior Resident Agent-Honolulu, Hawaii
P.O. Box 50223
300 Ala Moana Boulevard, Room 7-235
Honolulu, Hawaii 96850
Carr, G.D. 1985. "Monograph of the Hawaiian Madiinae (Asteraceae): Argyroxiphium, Daubautia, and Wilkesia." Allertonia 4:1-123.
Cuddihy, L.W., and C.P. Stone. 1990. Alteration of Native Hawaiian Vegetation: Effects of Humans, Their Activities, and Introductions. Cooperative National Park Resources Study Unit, University of Hawaii Press, Honolulu.
St. John, H., and G.D. Carr. 1981. "Two New Species of Dubautia (Compositae) from Kauai." Bulletin of the Torrey Botanical Club 108:198-204.
Stone, C.P., and J.M. Scott, eds. 1985. Hawaii's Terrestrial Ecosystems: Preservation and Management. Cooperative National Park Resources Study Unit, University of Hawaii Press, Honolulu.
U.S. Fish and Wildlife Service. 1994. "Recovery Plan for the Wahiawa Plant Cluster: Cyanea undulata, Dubautia pauciflorula, Herperomannia lydgatei, Labordia lydgatei and Viola helenae." U.S. Fish and Wildlife Service, Portland, Oregon.
Wagner, W.L., D.R. Herbst, and S.H. Sohmer. 1990. Manual of the Flowering Plants of Hawai ' i. University of Hawaii Press and Bishop Museum Press, Honolulu.