Polystichum aleuticum C. Chr.:
Canada (North America)
Mexico (Mesoamerica)
United States (North America)

United States

Origin: Native

Regularity: Regularly occurring

Currently: Present

Confidence: Confident

Type of Residency: Year-round

Global Range: Very narrow endemic, now known from only 3 rock outcrops on Mt. Reed, Adak I. Historically also known from Atka I. Nearest location of a closely related taxon is Honshu, Japan.

Historic Range:
U.S.A. (AK)

Polystichum aleuticum is known only from Atka and Adak islands, Alaska. Its nearest relatives are in southwest China. Polystichum aleuticum resembles the dwarfed plants of P . kruckebergii , but it differs, especially, in its smaller, more rounded pinna apices and more abundant scales.

Stems erect. Leaves monomorphic, erect, 1--1.5 dm; bulblets absent. Petiole 1/6--1/4 length of leaf; scales tan, sparse or falling off early. Blade linear-lanceolate, 1-pinnate, gradually tapered to base. Pinnae ± deltate to ovate, slightly overlapping, in 1 plane, 4--8 mm; base truncate, acroscopic auricle well developed; margins denticulate, not spiny; apex rounded, not dentate; microscales linear, lacking projections, dense on both surfaces. Indusia entire to minutely erose-dentate. Spores brown.

The small, simply-pinnate fronds with spiny-toothed pinnae and distinctive chestnut-brown stipe bases readily distinguish P. aleuticum from all other ferns in the Aleutian Islands. In the alpine habitat where P. aleuticum has been found, only immature or sterile individuals of Cystopteris fragilis (L.) Bernh. are at all similar, but these lack the straw-colored scales and stout chestnut-brown stipe bases of P. aleuticum and have leaves that are more dissected. Woodsia alpina (Bolton) S.F. Gray (not found in the Aleutian Islands) resembles P. aleuticum in size and form but has an indusium of hairlike segments in contrast to the peltate indusium of P. aleuticum. P. lonchitis, which is found in similar areas to P. aleuticum, is much larger and coarser, with coriaceous leaves.

Type collection for Polystichum aleuticum C. Chr.
Collection: Smithsonian Institution, National Museum of Natural History, Department of Botany
Verification Degree: Verified from the card file of type specimens
Preparation: Pressed specimen
Collector(s): W. Eyerdam
Locality: Alaska, United States, North America

Comments: SUMMARY: Cliffs and and rock outcrops on east-facing volcanic slopes at 365 to 525 m elevation. Found in protected gullies and grottos and on ledges, commonly associated with roundleaf willow (Salix rotundifolia), Alaska large awn sedge (Carex macrochaeta), and mosses. END SUMMARY. Polystichum aleuticum is found in moderately protected sites on east-facing slopes characterized by steep cliffs and rock outcrops with numerous overhangs and vegetated gullies and ledges. Underlying rocks are Finger Bay Volcanics-massive and intensely altered andesitic and basaltic flows and pyroclastic rocks. Soils are typic cryandepts, cryofolists, and lithic cryofolists (Lipkin, 1985). They are associated with three vegetation types: (1) A Salix rotundifolia-moss type occupying rocky, protected alcoves and cliff ledges under overhanging rock walls (5 plants grow in rock cracks and fractures and on cliff faces); (2) a moist Salix rotundifolia- Carex macrochaeta (P. aleuticum)-moss type in the more exposed and better drained mid- to upper portions of the rock gullies; (3) a moist lower gully-cliff base type of Carex macrochaeta-Anemone narcissiflora-Arnica unalaschensis- (P. aleuticum)-moss. In drier vegetation types, P. aleuticum grows in clumps on the edge of vegetation mats along rock walls and on the edges of sod clumps or mats that cap exposed rocks or rock outcrops. As cliff walls and rock faces become more rounded and less angular, with fewer cracks and overhangs, sites are more exposed to the elements, and the area is less likely to provide a protected environment for the fern and the compliment of moister site species it is generally associated with. P. aleuticum is not found in the Empetrum nigrum-lichen-moss heath that characterizes these higher elevation sites, nor does it occur beyond the cliff bases at its lower distributional limit, where the vegetation is a dense, moist to wet, sedge forb meadow association of Ranunculus escholtzii-Carex macrochaeta. At these lower elevations fronds are buried in the vegetation mat or growing out from under dense, sod overhangs. (Tande, 1989)

Growing in crevices of rocks; of conservation concern; 0--400 m; Alaska.

Known Pests: None KNOWN; HOWEVER UNIDENTIFIED RUST OBSERVED ON OCCASION.

Note: For many non-migratory species, occurrences are roughly equivalent to populations.

Estimated Number of Occurrences: 1 - 5

Comments: The species is currently known, globally, from only four locations, all on Mt. Reed, Adak I., the Aleutians. A fift population on Mt. Reed was reported (U88SMI01AKUS) but has not been verified as either extant or distinct from the other four EO's. The type locality on Atka I. (100 mi east of Adak I.) has not been located since it's discovery in 1932. Mt. Reed, Adak I., Atka I. and other islands in the chain have been surveyed for several years, but much additional work is needed before conclusive statements on total EO's can be made.

United States

Rounded National Status Rank: N1 - Critically Imperiled

Rounded Global Status Rank: G1 - Critically Imperiled

Reasons: A narrow endemic that occurs in very low numbers and in highly unstable habitats. Only 4 small occurrences are currently known, all on 1 island in the Aleutian Islands, Alaska. This species apparently has a low rate of reproduction.

Environmental Specificity: Narrow. Specialist or community with key requirements common.

Current Listing Status Summary

Status: Endangered
Date Listed: 02/17/1988
Lead Region:   Alaska Region (Region 7) 
Where Listed:


Population detail:

Listing status: E

For most current information and documents related to the conservation status and management of Polystichum aleuticum, see its USFWS Species Profile

Global Short Term Trend: Unknown

Comments: Sites have not been monitored since early 1990's.

Global Long Term Trend: Unknown

Comments: Occurrence in very low numbers and in highly unstable habitats suggests a high degree of natural threat to this species. Man made threats are low at present and limited to over collecting, incidental habitat disturbance by either hiking or climbing in the area, and possible grazing by introduced caribou. Increased tourism, hunting, and ATV use on Adak adversely affect the populations.

Biological Research Needs: More work is needed on reproductive biology, propagation, and on the relation of this species to P. lachenense.

Needs: When occurrence of species is updated, coordinate protection activities with refuge manager.

Comments: Polystichum aleuticum is a narrow endemic with no closely related taxa in the western hemisphere. It is apparently a Tertiary relict, whose closest affinities are with P. lachenense, which occurs in the Himalaya, China, and northern Japan and also with Himalayan P. sinense. Further study is needed to clarify the relation between these two taxa. Lellinger, in his 1992 revised edition, treats P. aleuticum as conspecific with P. lachenense. He includes no discussion and provides no justification for this treatment.