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Ctenitis squamigera

ListedSeptember 26, 1994
FamilyDryopteridaceae (Wood fern)
DescriptionDense covering of tan-colored scaleson its fronds.
HabitatForest understory at elevations of 1,250-3,000 ft (381-914 m).
ThreatsHabitat degradation by feral pigs, goats, and axis deer; competition with alien plants.


The pauoa, Ctenitis squamigera, a member of the wood fern family (Dryopteridaceae), has a rhizome 0.2-0.4 in (1-2 cm) thick. This horizontal stem creeps above the ground and is densely covered with scales similar to those on the lower part of the leaf stalk. The leaf stalks are 8-24 in (20.3-50.8 cm) long and densely clothed with tan-colored scales up to 0.7 in (1.8 cm) long and 0.04 in (0.1 cm) wide. The leafy part of the frond is deltoid to ovate-oblong, dark green, thin, and twice-pinnate to thrice pinnatifid (leaflet sections). The sori, tan-colored when mature, are in a single row one-third of the distance from the margin to the midrib of the ultimate segments. The indusium is whitish before wrinkling, thin, suborbicular with a narrow sinus extending about half way, and glabrous except for a circular margin that is ciliolate with simple several-celled glandular and nonglandular hairs arising directly from the margin or from the deltoid base.

C. squamigera can be readily distinguished from other Hawaiian species of Ctenitis by the dense covering of tan-colored scales on its fronds.


This species is found in the forest understory at elevations of 1,250-3,000 ft (381-914.4 m), in Ohial Diospyros (lama) mesic forest and diverse mesic forest. Associated native plants include Myrsine (kolea), Psychotria (kopiko), and Xylosma hawaiiense (maua).


C. squamigera had historical occurrences from above Waimea on Kauai; Kaluanui, southeast of Kahana Bay, Pauoa, Nuuanu, Niu, and Wailupe in the Koolau Mountains of Oahu; Mt. Kaala Natural Area Reserve and Schofield Barracks in the Waianae Mountains of Oahu; at Kalnaaha Valley on Molokai; in the mountains near Koele on Lanai; in the Honokohau Drainage on West Maui; at Manawainui Stream on East Maui; and at "Kalua" on the island of Hawaii. The ten populations that have been observed within the last 20 years occur on Oahu in the Waianae Mountains, Lanai, East and West Maui, and Molokai. The Waianae Mountain populations are in Makaleha Valley, Kaawa Gulch, Maku Valley, and Waianae Kai Forest Reserve. C. squamigera occurs on Lanai in the Waiapaa-Kapohaku area on the leeward side of the island and at Lopa Gulch and Waiopa Gulch on the windward side. The West Maui populations are in Iao Valley and Kapunakea Preserve. The Molokai population is in Wawaia Gulch. The ten populations on Federal, state, and private land totaled approximately 100 individuals in 1995.


The primary threats to C. squamigera are habitat degradation by feral pigs, goats, and axis deer; competition with alien plants, especially strawberry guava and Christmas berry; fire; and stochastic extinction due to the small number of existing populations and individuals. Habitat degradation caused by axis deer is now considered a major threat to the forests of Lanai. All three of the Lanai populations of C. squamigera are negatively affected to some extent by axis deer.

Conservation and Recovery

The U. S. Army has prepared Endangered Species Management Plans for training areas on the island of Oahu, highlighting specific threats to endangered plants and recommending actions to promote recovery.

On Lanai, building exclosures around some of the most intact portions of native forest in conjunction with hunting would provide good protection for endangered species, including C. squamigera.

Oahu populations of C. squamigera would benefit from the proposed expansion of the Mt. Kaala Natural Area Reserve to include Waianae-Kai Forest Reserve and Makaleha Valley Forest Reserve.


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. 1998. "Recovery Plan for Four Species of Hawaiian Ferns." U.S. Fish and Wildlife Service, Portland, Oregon. 78 pp.