No Common Name
|Listed||February 25, 1994|
|Description||Tufts of three to four light green, lance-shaped dark purple to brownish gray fronds with short black hairs on the underside.|
|Habitat||Bare soil on steep, rocky dry slopes of lowland mesic forests.|
|Threats||Goats, pigs, deer, alien plants, fire, limited numbers.|
Diellia pallida is a plant in the spleenwort family that grows in tufts of three to four light green, lance-shaped fronds along with a few persistent dead ones. The midrib of the frond ranges from dark purple to brownish grey in color and has a dull sheen. Scales on the midrib are brown, grey or black, about 0.1 in (2.5 mm) long, and rather inconspicuous. The fronds, measuring 12-22 in (30-60 cm) in length and 2-5 in (5-12 cm) in width, have short black hairs on the underside. Each frond has approximately 20-40 pinnae (divisions or leaflets). The largest pinnae are in the middle section of the frond, while the lower section has triangular, somewhat reduced pinnae, with the lowermost pair of pinnae raised above the plane of the others. The groups of spore-producing bodies known as sori are encircled by a prominent vein and frequently fused along an extended line. This species differs from others of this endemic Hawaiian genus by the color and sheen of the midrib, the presence and color of scales on the midrib, and the frequent fusion of sori.
Diellia pallida grows in bare soil on dry, rocky, and steep slopes of lowland mesic forests at elevations of 1,700-2,300 ft (520-700 m).
Diella pallida was known historically from Hale-manu on Kauai. This species, unobserved since 1949, was collected again in 1987 from Kuia Natural Area Reserve.
The three current populations of 23 total plants occur over a 3 by 7 mi (5 by 11 km) area of state-owned land at Mahanaloa Valley and Makaha Valley within Kuia National Area Reserve and Koaie Canyon; a count in 1994 found 10 and 12 individuals, respectively, in the first two locations and only one plant at Koaie Canyon. Eight of the plants in the Makaha Valley population were juveniles.
Competition with alien plants, especially lantana and Chinaberry, constitutes the major threat to this species. St. Augustine grass, basketgrass, and other fast-growing weeds degrade D. pallida habitat. Feral goats trample D. pallida individuals and cause soil erosion by their relentless browsing in and around the plants. Other threats include habitat degradation by mules and deer, fire, over-collecting for scientific purposes, and reduced reproductive vigor.
Conservation and Recovery
The only two known populations of the Diella pallida are on state land on Kauai, within the Kuia Natural Area Reserve and in Koaie Canyon. These populations must be strictly protected. They should be fenced to exclude introduced mammalian herbivores, particularly goats. The abundance of threatening non-native plants, especially lantana and Chinaberry, should be aggressively reduced in the habitat of the endangered fern. Its populations should be monitored, and research undertaken into its biology and habitat needs. Work should be undertaken on the propagation of Diella pallida in captivity, with the long-term goal of out-planting to supplement the perilously small wild population.
U.S. Fish and Wildlife Service
Pacific Islands Ecoregion
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
Regional Office, Division of Endangered Species
Eastside Federal Building
911 N. E. 11th Ave.
Portland, Oregon 97232-4181
Telephone: (503) 231-6121
U.S. Fish and Wildlife Service. 25 February 1994. "Endangered and Threatened Wildlife and Plants; Determination of Endangered or Threatened Status for 24 Plants from the Island of Kauai, Hawaii." Federal Register 59.