Polystichum aleuticum, the Aleutian holly fern or Aleutian shield fern, is an endangered species of the Polystichum genus and currently consisting of a small, vulnerable population endemic found only on Adak Island, Alaska, a remote island of the Aleutian Islands chain in the northern Pacific Ocean. This species grows on steep, windswept slopes with thin, rocky soils, often in sites exposed to salt spray and harsh subarctic weather, conditions that likely contribute to its limited distribution. In 1992, 112 specimens existed in the wild, and following its listing as endangered in 1988, a recovery plan was implemented. The U.S. Fish and Wildlife Service developed a recovery plan outlining habitat protection, population monitoring, and research on the species’ biology. Periodic 5-year reviews have continued to evaluate population trends and management needs. The Aleutian shield fern is the only native plant of Alaska on the federal endangered species list. As there are fewer than 150 plants known to exist, it is a very rare North American plant making it an important focus of botanical conservation in the state. Major threats include landslides, harsh storms, and trampling by wildlife, and its tiny range makes the remaining populations especially vulnerable to chance events. Polystichum aleuticum was first described in 1938, but it could not be located again until 1975 when a group was identified on Mount Reed on Adak Island. A second, third, and fourth population, all on Mount Reed, was located in 1988, 1993, and 1999, respectively. Searches on other Aleutian Islands since 1988 have failed to identify additional populations.

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