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COSEWIC assessment and status report on the Boreal Felt Lichen in Canada

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COSEWIC
Executive Summary

Boreal Felt Lichen
Erioderma Pedicellatum

Species Information

Boreal felt lichen (Erioderma pedicellatum) is a globally threatened, conspicuous foliose cyanolichen belonging to the Pannariaceae. It is the only boreal counterpart of a mainly tropical genus. The thallus is of a grayish brown colour when dry and a slate blue colour when moistened. It has a characteristic white underside, lacking a lower cortex. The curled to upturned lobes give it a unique appearance when viewed from a distance. New biochemical evidence suggests that the genus may be among the oldest of foliose lichens, hybridized from ancestral types, perhaps well over 400 million years ago (mya). Hybridization between an ancestral species and a mutant of it in South America likely gave rise to the boreal felt lichen. This new entity could have been transported on the microcontinent of West Avalonia to present day New England, New Brunswick, Nova Scotia and Newfoundland, and to the British Isles on the microcontinent of East Avalonia during Mid- to Late Ordovician (450-440 mya, departure time) and Devonian (360 mya or less, arrival time).

Distribution

The species once had a global Amphi-Atlantic distribution with populations occurring in New Brunswick, Nova Scotia and Newfoundland in Eastern Canada and Sweden and Norway in Scandinavia. Currently the species is only known from Nova Scotia and Newfoundland. 

Habitat

Habitats of the boreal felt lichen may be referred to as the Suboceanic Lichen Forests of Atlantic Canada both because of the moist, Sphagnum-rich sites and because of the presence of a distinct cyanolichen community including E. pedicellatum. These suboceanic sites where Erioderma is found are generally on north or east-facing slopes that have a constant supply of moisture. Within these sites, the species is found mostly on balsam fir (Abies balsamea) and to a lesser extent on black spruce (Picea mariana) with rare occurrences on white spruce (Picea glauca), red maple (Acer rubrum) and white birch (cf. Betula cordifolia). On the coniferous trees mentioned, it can be found on both branches and trunks depending on the relationship between the level of moisture and light. It is known that this lichen shares an intimate relationship with the liverwort Frullania tamarisci ssp. asagrayana. The co-occurrence of Erioderma and Frullania is a visible external manifestation of the widespread internal symbiosis between Frullania and its cyanobacteria. Both Scytonema and Nostoc have been found to occur within the watersacs of Frullania. This intimate external symbiosis represents one of the delicate and complex relationships that this lichen shares with its ecosystem and for that reason its ecological balance is fragile and readily impacted by logging, air pollution and other factors.

Biology

Boreal felt lichen is a large foliose lichen with a generation time of about 30 years. It reproduces by sexual spores that are carried, likely, primarily by wind but also by other vectors such as flying insects and woodpeckers. No special asexual propagules are produced. One study has suggested that lichenization between the germinating ascospore and free-living Scytonema, a cyanobacterium (blue-green alga), can occur only in the water sacs of Frullania, a small, epiphytic, leafy liverwort. The relationship is such that the early synthesis of the lichen begins in the watersacs of Frullania wherein the free-living, cyanobacterial counterpart, Scytonema, is contained and comes into physical contact with Erioderma hyphae. Here under aseptic conditions the juvenile Erioderma thallus is formed and may take anywhere from 5-10 years to reach a visible size. Because of the presence of Scytonema, the lichen is particularly sensitive to acid rain, acid fog and other air pollutants. It requires relatively cool and moist oceanic climates within certain tolerances and open canopy for juvenile thalli to develop. Mature thalli deteriorate on trees that are mature to overmature or dead, seemingly in a span of only a few years. Thalli also deteriorate when habitat succession occurs that reduces light availability and when microclimatic conditions seem to be altered by extensive logging in close proximity to the lichen. Its occurrence on the particularly acidic bark of spruce trees reduces its ability, compared to fir trees, to survive when stressed by acidic air pollutants.

Population Sizes and Trends

Historically, E. pedicellatum occurred in Scandinavia but is now seemingly extirpated there. In considering all past and present confirmed occurrences, the range of the lichen in North America covers Campobello Island in New Brunswick, Cape Chignecto (alt. 136 m), the Atlantic slope of Nova Scotia at altitudes between 8 and 150 m, and the suboceanic parts of Newfoundland to an elevation of ~ 427 m. In Newfoundland, it is conspicuously absent from the eastern parts of the Great Northern Peninsula and from the northern central parts of the island. All of the 6 previously known localities for E. pedicellatum in southern Nova Scotia have been lost within the past 8-18 years. Environmental deterioration of the habitats through air pollution rather than through logging is the underlying cause for this change. Only 14 thalli are presently known to occur in Nova Scotia, as opposed to 169 thalli that had been encountered before 1995. In Newfoundland, about 6900 thalli of E. pedicellatum have been counted during the period after 1994, with about 35% of these having been documented in early 2002 by provincial foresters. The vast majority of the thalli were found on balsam fir with a much lower number on black spruce, the occasional thallus on white spruce, and a few on red maple and white birch. The total area of occupancy within which thalli have been documented in Newfoundland is about 30 km2 of habitat but likely consists of a much larger area when inaccessible areas along the south coast are included.

Limiting Factors and Threats

The species is in danger of population loss due to a number of threats. Perhaps the greatest threat is from logging, which is presently a major concern in Newfoundland. Clear-cutting is not conducive to the sustainability of Erioderma populations since clearcuts of 100 m x 100 m or more may act to desiccate local populations. This was historically the case in Vãrmland, Sweden, where logging in the immediate vicinity of the park where the Eriodermathalli occurred was the suspected cause of the eventual extirpation of this species. Other threats involve air pollution, forest pesticides, forest fires, climatic changes including global warming and moose herbivory on balsam fir seedlings.

Special Significance of the Species

Boreal felt lichen has served as a landmark species drawing attention to the need for lichen conservation. It is an ancient species whose fungal partner is believed to have evolved almost 500 mya. Its high susceptibility to air pollutants, perhaps more so than any other lichen species, makes it a prime candidate for monitoring changes in air quality.

Existing Protection or Other Status Designation

The species had originally been listed in 1995 as critically endangered in the “Red List of Lichenized Fungi of the World” by the Species Survival Commission (SSC) of the Lichen Specialist Group, International Union for the Conservation of Nature (IUCN). 

No official status is recognized for Erioderma pedicellatum in any of the three Atlantic Provinces where it has occurred historically. Preliminary conservation measures had only been initiated in Newfoundland in response to recent suggestions by Dr. Christoph Scheidegger. Legal protection has existed for the large population in Jipujijkuei Kuespem Provincial Park as well as for populations in the Bay du Nord Wilderness Area and the Avalon Wilderness Area although these areas were not established specifically to protect this lichen. Interim protection was afforded, also, through an earlier promise made to Dr. Christoph Scheidegger and the ICCL in 1996, by then Premier Brian Tobin, that the Lockyer’s Waters Forest Area would not be harvested until the status of the boreal felt lichen had been determined by COSEWIC.

Summary of Status Report

Boreal felt lichen is a conspicuous foliose lichen that is found primarily on balsam fir in a very restricted type of cool moist suboceanic habitat. It is extirpated from its type location in New Brunswick where it was first reported in Canada. This species occurs now at only 3 sites with about 13 thalli in Nova Scotia and about 67 known sites on the island of Newfoundland. Only about 6900 extant thalli have been documented in total for the species in Canada. Of these, about 35% were discovered in Newfoundland in the spring of 2002 with renewed efforts to locate additional thalli. Considering that there are many forested riparian valley habitats with balsam fir in remote areas of the south coast of Newfoundland, it is highly likely that there are many more sites and numerous thalli yet to be discovered. Continued threats remain from the loss or modification of habitats through lumbering activities and from air pollutants.

For assessment purposes, the mainland populations in Nova Scotia and those of insular Newfoundland have been recognized as distinct COSEWIC populations due to the fact that they occur in different ecological regions and are subject to different degrees of risk, especially from atmospheric.