Thelypteris yaucoensis

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Thelypteris yaucoensis

No Common Name

ListedJuly 2, 1993
FamilyThelypteridaceae (Marsh fern)
DescriptionA ground fern.
HabitatSteep, shaded, rocky banks and ledges at high elevations in cloud forest.
ThreatsHabitat loss by development or hurricanes, and collecting for horticultural use.
RangePuerto Rico


Thelypteris yaucoensisis a terrestrial fern with erect rhizomes, 0.02 in (0.5 mm) thick, and covered at the apex with a tuft of brown, 0.2-0.3 in (5-8 mm) long scales. There are few fronds, which are 17-20 in (44-52 cm) long, and are lustrous, light-brown, hairless, and born on a stipe (stem) 7-9 in (18-22 cm) long. The blade of the frond is oblong, 10-13 in (25-31 cm) long, 4-6 in (10-14 cm) wide, and has 13-15 pairs of alternate pinnae (or lobes). The spore-producing structures (or sori) have minute forked and three-branched hairs, and have a small covering tissue (or indusium).


T. yaucoensis is found in humid tropical cloud-forest on steep, shaded, rocky banks and ledges at high elevations (2,800-3,900 ft; 850-1,200 m).


T. yaucoensis is a locally evolved (or endemic) species that is only known from three localities in Puerto Rico: from Barrio Rubias in the municipality of Yauco, Los Tres Picahos in Barrio Toro Negro in Ciales, and the summit area of Pico Rodadero, Barrio Sierra Alta in the municipality of Yauco.


The total known population of T. yaucoensis consists of only about 65 plants. All of the habitat of the rare fern is privately owned, and is therefore threatened by clearing and other disturbances. Because of its extreme rarity, this fern might be an attractive item for illegal collecting for sale in the horticultural trade. Due to its tiny population and restricted range, this fern is also extremely vulnerable to the devastation of its habitat by a hurricane.

Conservation and Recovery

The critical habitat of T. yaucoensis is entirely located on private land. This habitat should be protected by acquisition and the establishment of ecological reserves, or by the negotiation of conservation easements. The rare fern must also be strictly protected from any collection of specimens. In addition, research should be conducted on its biology and habitat requirements, to provide knowledge for its management.


U. S. Fish and Wildlife Service
Regional Office, Division of Endangered Species
1875 Century Blvd., Suite 200
Atlanta, Georgia 30345
U. S. Fish and Wildlife Service
Boquerón Ecological Services Field Office
P. O. Box 491
Boquerón, Puerto Rico 00622-0491
Telephone: (787) 851-7297
Fax: (787) 851-7440


U. S. Fish and Wildlife Service. 2 July 1993. "Endangered and Threatened Wildlife and Plants: Determination of Endangered Status for Three Endemic Puerto Rican Ferns." Federal Register 58(126):35887-35891.

U. S. Fish and Wildlife Service. 1994. "U. S. Fish and Wildlife Service, Division of Endangered Species, Species Accounts: Three Endemic Puerto Rican Ferns." U. S. Fish and Wildlife Service Endangered Species Program. ( Date Accessed: July 5, 2000.