Searching for Ferns

Searching for Ferns

Fairchild Tropical Botanic Garden

Based on report by FTBG and University of Florida staff to USFWS

Ferns abound on the Island of Enchantment – Puerto Rico. The U.S. territory is home to many species of ferns, including 22 endemic species found nowhere else. While stunning tree ferns may capture the attention of island visitors who venture away from the beaches and into the forest, rare endemics are the prize that botanists from Fairchild Tropical Botanic Garden have been seeking.

Fairchild staff recently concluded a multi-year project with the U.S. Fish and Wildlife Service (USFWS), focused on the island’s eight federally listed endemic ferns.

Background photo: The team’s 2014 survey at Silla de Calderon resulted in spores of Polystichum calderonense that were eventually propagated at Fairchild’s nursery. Photo credit: Jennifer Possley, courtesy of Fairchild Tropical Botanic Garden.

Searching for Ferns

Fairchild Tropical Botanic Garden, Based on report by FTBG and University of Florida staff to USFWS

Ferns abound on the Island of Enchantment – Puerto Rico. The U.S. territory is home to many species of ferns, including 22 endemic species found nowhere else. While stunning tree ferns may capture the attention of island visitors who venture away from the beaches and into the forest, rare endemics are the prize that botanists from Fairchild Tropical Botanic Garden have been seeking.

Fairchild staff recently concluded a multi-year project with the U.S. Fish and Wildlife Service (USFWS), focused on the island’s eight federally listed endemic ferns.

Photo: The team’s 2014 survey at Silla de Calderon resulted in spores of Polystichum calderonense that were eventually propagated at Fairchild’s nursery. Photo credit: Jennifer Possley, courtesy of Fairchild Tropical Botanic Garden.

Despite extreme rarity and acute threats, these species had been poorly studied beyond their initial scientific description. In many cases, we don’t even know if their populations still exist. Access and identification present significant challenges. Basic questions remain unanswered, such as whether the species represent valid taxa, distinct and capable of reproduction. To begin addressing some of these issues, staff from Fairchild joined forces with partners from USFWS, the Department of Natural and Environmental Resources, University of Puerto Rico, and the University of Florida to seek out these elusive fern populations. Their goals were to document and quantify occurrences, attempt propagation for the development of ex situ conservation collections, and conduct genetic analyses to determine the phylogenic status of questionable taxa.

These were not quick and simple tasks. Progress towards understanding and conservation was greater for some species than for others. Beginning in 2014, the group made three field surveys to visit or search for seven of these eight taxa – not attempting to visit Thelypteris inabonensis due to its remote locations and the limited timeframe of the trips.

The Fairchild team is well-versed in identifying the native species and ferns in the Miami region. Because the biogeographical roots of many South Florida plants lie in the nearby islands, knowledge of native species in Miami aids in identification of many island species, or at least their close relatives. Team members Jennifer Possley and Jimmy Lange often seek opportunities to use their experience with Miami’s ferns to promote fern conservation throughout the larger region.

Even so, the group struggled with certain taxa. Two surveys failed to find Elaphoglossum serpens in its last known locality (Cerro Punta) – supporting the commonly held belief that this occurrence, like the type locality, was extirpated (completely wiped out) during the construction of a cell-tower. Efforts to make collections of Thelypteris yaucoensis also came up dry, in part due to difficulty in distinguishing this endemic fern from other taxa in the Goniopteris group of Thelypteridaceae.

Photo of conservationists studying specimens in UPR herbarium

Before field surveys, Jimmy (above) and Jennifer studied specimens in the University of Puerto Rico herbarium at Mayaguez to better familiarize themselves with targets species. Photo credit: Jennifer Possley, courtesy of Fairchild Tropical Botanic Garden.

Photo of conservationist checking out a fern

Goniopteris— is it Thelypteris verecunda or not? Hmm. Fern identification can be incredibly difficult, hindering the progress for some of the species and pointing to the need for more research.

Omar Monsegur-Rivera and Barbara Sanchez look for Thelypteris verecunda beneath a bridge. Photo credit: Jennifer Possley, courtesy of Fairchild Tropical Botanic Garden.

Photo of USFWS biologist Omar Monsegur Rivera in newly discovered valley

USFWS biologist Omar Monsegur-Rivera (this month’s Conservation Champion), here in the newly discovered valley with dozens of Cyathea dryopteroides, was instrumental in the realization of this collaborative project.

Photo of FTBG team processing specimens

The team processes specimens after a day of field work in Puerto Rico. Photo credit: Jennifer Possley, courtesy of Fairchild Tropical Botanic Garden.

Photo of Cyathea dryopteroides sori after spore release

Cyathea dryopteroides sori after spore release. Not producing flowers, ferns have a multi-stage reproductive process that begins with the release of spores from structures under the leaves known as sori. Spores are often the material collected for ex situ collection, and stored in cryobanks such as those at NLGRP.

Field collections were more fruitful for Adiantum vivesii, Tectaria estremerana, and Thelypteris verecunda. Field surveys for these three ferns were followed by genetic studies led by Dr. Emily Sessa and graduate student Lindsey Riibe at the University of Florida. The studies were designed to advance understanding of the very complicated relationships between these rare taxa and their more common relatives. Results suggest that all three of the taxa are of hybrid origin. At least one, A. vivesii, is unlikely to be a distinct taxon – when combined with previous research on its lack of reproduction, the team believes there is support for its delisting. Interestingly, sequencing results for other hybrid Adiantum specimens examined in this study revealed that they may in fact be valid polyploidy (having multiple chromosome sets) taxa in need of formal descriptions and subsequent evaluation of conservation status. Further studies into spore morphology and viability are needed to determine whether T. estremerana and T. verecunda are true species and therefore in need of legal protection.

The biggest conservation progress was made with Cyathea dryopteroides and Polystichum calderonense. The field work was simplified by the fact that the species were already familiar to local USFWS and DNER staff, including this month’s Conservation Champion, Omar Monsegur-Rivera. The increased intensity of surveys during this study, however, increased the number of known individuals of several populations, particularly of C. dryopteroides at Cerro Punta which increased from four to at least 55 plants. As a result of this program, both species have now been successfully cultivated at Fairchild Tropical Botanic Garden, and spores have been cryogenically stored at the USDA National Laboratory for Genetic Resources Preservation (NLGRP) in Ft. Collins, Colorado. The sharing of living material among several botanical institutions has further safeguarded germplasm. In addition, some potential reintroduction habitat has been evaluated and described. Recovery actions, such as reintroductions or augmentations, are therefore very possible in the next decade for both C. dryopteroides and P. calderonense.

Fairchild’s nursery is flush with C. dryopteroides and P. calderonense grown from spores collected during early field surveys. Twenty-three C. dryopteroides are happy and healthy in one-gallon pots, often producing sporangia (spore-forming enclosures on the plants) each winter. The garden’s ex situ collection of 90 healthy Polystichum calderonense individuals has spawned hundreds of small sporophytes in germination boxes. Because this abundance far exceeds the available fern-growing space in Fairchild’s nursery, they sent spore boxes to cooperating institutions, five of which are now cultivating P. calderonense in their greenhouses.

The fern project proved to be productive for all the collaborators and for the conservation of Puerto Rico’s special endemic ferns. However, much remains be done. Continued field work was already clearly necessary for many of the species, and the impacts of Hurricane Maria (2017) and other storms present new unknowns. The project also highlights the potential of ex situ collections in fern conservation on the island. Despite the large number of rare and endemic ferns, none had been secured in ex situ collections prior to this project. Now Fairchild Tropical Botanic Garden holds living collections, and the National Laboratory for Genetic Resources Preservation  holds cryogenically-preserved spores that serve as backstops against extinction for these unique ferns.

Photo of Thelypteris yaucoensis

Thelypteris yaucoensis

Photo of Thelypteris verecunda

Thelypteris verecunda

Photo of Thelypteris inaboensis

Thelypteris inaboensis

Three of the federally listed endemic ferns of Puerto Rico the team studied are species of the genera Thelypteris, a group often known as maiden ferns.

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2020-05-05T18:59:30+00:00