Na'ena'e (Dubautia plantaginea ssp. humilis)
Dubautia plantaginea ssp. humilis
|Listed||September 3, 1999|
|Description||A tropical dwarf shrub.|
|Threats||Habitat loss, invasive non-native plants, and hurricanes.|
The na'ena'e is a dwarf shrub, growing less than 30 in (80 cm) tall. Its stems are hairless, or occasionally have straight hairs pressed against the stem. The leaves are arranged in opposite fashion on the stem, and are narrow, 3-6 in (8-15 cm) long, and 0.3-1.8 in (0.7-4.5 cm) wide. The leaves have 5-9 nerves, and are hairless or moderately long hairy. The leaf margins are toothed from the apex to near the middle. Each inflorescence contains 20 to 90 flowering heads, and in total is about 8 in (20 cm) long and 11 in (28 cm) wide. Each flowering head contains 8 to 20 florets (an individual, small flower, that is part of a dense cluster), arranged on a flat receptacle. The bracts on the receptacle are about 0.2 in (5 mm) long, sharply toothed, and fused together. The corolla is yellow, and may purple with age. The fruit is an achene (a dry, one-celled, indehiscent fruit) 0.08-0.2 in (2.5-4 mm) long.
The habitat of the na'ena'e is wet, barren, wind-blown cliffs, between 1,150 and 1,300 ft (350-400 m) in elevation. Associated native plants include the ohi'a (Metrosideros polymorpha ), mamaki (Pipturus albidus ), kawelu (Eragrostis variabilis ), loulu (Pritchardia sp.), kookoolau (Bidens sp.), and the endangered ale (Plantago princeps ).
The na'ena'e is a locally evolved (or endemic) plant that has only been reported from two locations in Iao Valley, on West Maui. The Hawaiian archipelago has an extremely large fraction of endemic species; about 89% of the indigenous flowering plants occur nowhere else in the world.
The na'ena'e is threatened by competition and habitat change associated with alien species of plants, and by natural landslides in its cliff habitat. The most important of the non-native plants include the common guava (Psidium guajava ), ironwood (Casuarina equisetifolia ), sourbush (Pluchea symphytifolia ), and smutgrass (Sporobolus africanus ). Because there are only two small, known populations occurring less than 0.5 mi (0.8 km) apart within the same valley, the rare plant is also threatened by catastrophic disturbance associated with hurricanes. The two known populations of the na'ena'e are on privately owned land, and total fewer than 300 individuals.
Conservation and Recovery
The na'ena'e survives only on private land, and therefore its habitat is potentially at risk. Conservation of this endangered plant requires that its habitat be secured through acquisition and designation as an ecological reserve, or by the negotiation of a conservation easement. The abundance of non-native plants in its habitat must be actively reduced. The surviving populations of the na'ena'e should be monitored, and research undertaken to better understand the environmental factors limiting its abundance, with a view to enhancing its populations through management.
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
Pacific Islands Ecoregion, Pacific Islands Fish and
300 Ala Moana Boulevard, Room 3-122
P. O. Box 50088
Honolulu, Hawaii 96850
Telephone: (808) 541-3441
Fax: (808) 541-3470
U. S. Fish and Wildlife Service. 3 September 1999. "Endangered and Threatened Wildlife and Plants: Final Endangered Status for 10 Plant Taxa from Maui Nui, Hawaii." Federal Register 64 (171): 48307-48324.