The Big Search for Tiny Ferns

Hunting for tiny fern gametophytes under a rotted tree in the rainforest near Sitka, Alaska. Critical equipment includes a magnifying glass and a flashlight. 

Coastal rainforest habitat where Hymenophyllum wrightii was found near Tofino, British Columbia on the west coast of Vancouver Island. Photo by Aaron Duffy. 

Hymenophyllum wrightii gametophytes growing in a tangled clump on rotting wood. Photo by Aaron Duffy.

For many years, Forest Service botanists have been interested in finding an elusive plant called Wright’s filmy fern (Hymenophyllum wrightii) in the Alaska Region. The fern was designated by the Regional Forester as an Alaska Region Sensitive Species in 1994 because of its apparent rarity. However, interest in the plant began several decades earlier.

 

 

In 1957, botanists discovered Wright’s filmy fern growing on the west side of the Queen Charlotte Islands (Haida Gwaii) in British Columbia. This was a significant find because the fern was previously known to grow only in Japan and Korea. The fern has two free-living (independent) generations in its life cycle. The plant we recognize as a fern is the sporophyte (spore producing generation) it has small, triangular, very delicate fronds that grow in loose mats, and the other generation (gametophyte) is tiny, (less than 1/32 of an inch wide), ribbon-like and branching, and often grows in tangled mats with mosses and liverworts.

 

 

In the late ‘50s and early ‘60s, botanists found the gametophytes at several sites in coastal British Columbia. Then in 1965, gametophytes were found on Biorka Island near Sitka, Alaska, and in 1968, more were discovered at three places in the Wrangell and Petersburg areas. 

 

 

Although Forest Service botanists continued over the years to search for both generations of the fern, we always came up empty handed. Then, Donald Farrar of Iowa State University taught us special techniques to carefully search for the tiny ferns where they grow in the darkest places on rotting stumps or downed trees. We then used three pieces of critical equipment to search for the fern: a flashlight, a magnifying glass and a rubber suit.

 

 

Brad Krieckhaus, botanist at the Sitka Ranger District, made the first modern find of the fern on the southwest side of Baranof Island in Summer 2005. Then, in 2006, I joined Farrar and Tongass Forest Ecologist Karen Dillman on another search. We not only found the gametophytes at Biorka Island and near Petersburg, but also at many other sites in southeastern Alaska. 

 

 

In 2008, Aaron Duffy of Utah State University conducted surveys on southwest Vancouver Island and on the western side of the Olympic Peninsula, and found gametophytes in both areas. His Olympic Peninsula find is the first report of Wright’s filmy fern in the contiguous United States. To determine if the gametophytes were in fact Wright’s filmy fern, Duffy conducted genetic analysis using samples of gametophytes from southeastern Alaska, British Columbia and Washington, as well as samples of Asian sporophytes. He determined that all of the samples were indeed Wright’s filmy fern.

 

 

From these surveys and genetic studies, we learned that Wright’s filmy fern gametophytes are not as rare as we thought. They are much overlooked due to their small size, resemblance to moss and liverworts, and easily overlooked habitat. Because of their relative abundance they were removed from the Alaska Region Sensitive Species List in 2009. So far, only the gametophytes have been found in Alaska, yet we will continue searching for the larger, leafy “more fern-like” sporophytes.

 

 

Although we now know more about where the gametophytes grow, we still do not know how readily they spread. In the bigger picture, these ferns may provide a window into an aspect of the history of west coast flora. Wright’s filmy fern may have migrated from Asia around the north Pacific Rim long ago.

 

 

The studies and results were published early in February 2015, in the American Fern Journal 105 (1):45-55.

 

 

You can find more Wright's filmy fern photos by  Aaron Duffy at https://www.flickr.com/photos/aduffy70/sets/72157651525511430/

 

 

By Mary Stensvold, Alaska Regional Botanist