Erioderma pedicellatum

Erioderma pedicellatum is a medium-sized, foliose lichen in the family Pannariaceae, commonly called boreal felt lichen because of its fuzzy appearance. It grows on trees in damp boreal forests along the Atlantic coast, as well as in southcentral Alaska and in Kamchatka. It is currently one of the most endangered lichens in the world. Erioderma pedicellatum is a foliose cyanolichen with lobes 2–5 cm across, and occasionally reaching 12 cm in diameter. It has a distinctively fuzzy upper surface that is greyish-brown when dry and slate-blue when moist. The underside is white, and its edges usually curl upwards, giving it the appearance of having a white fringe. It differs from the two other North American species of Erioderma by lacking soredia, and by having small, reddish-brown apothecia on its upper surface. Erioderma pedicellatum was first collected in 1902 from Campobello Island, Charlotte County, New Brunswick, Canada, by William Gilson Farlow. It was originally identified as a species of Pannaria and named P. pedicellata by French botanist Auguste-Marie Hue. It remained in this genus until 1972 when it was reexamined by the Norwegian botanist Per Magnus Jørgensen and placed in the genus Erioderma as E. pedicellatum. It is an unusual species within that genus, both because of its laminal apothecia (lacking in other Erioderma) and its boreal distribution. Erioderma pedicellatum has also been incorrectly called E. boreale. Erioderma pedicellatum is an amphi-Atlantic species that was once prevalent in Norway and Sweden as well as the provinces of New Brunswick, Nova Scotia, and Newfoundland in Atlantic Canada. Very recently, small populations were discovered in Denali area of Alaska and in Kamchatka, increasing the known range of the species. The last known population in Europe is located in Hedmark county, Norway. It has disappeared from Sweden and most areas of Atlantic Canada. It is no longer found in New Brunswick, and as of 2009 there were fewer than 200 individuals known in Nova Scotia. The remaining habitat in Newfoundland is therefore critical for the global survival of this species. Lockyer's Waters and Hall’s Gullies on the Avalon Peninsula in the southeast of Newfoundland, as well as Bay d'Espoir in the south, are three of the province's most prolific rare lichen habitats and are important for the conservation of Erioderma pedicellatum. This lichen grows on the mossy trunks and branches of trees on slopes in areas that have a constant supply of moisture and are rich in Sphagnum moss. It is usually found on balsam fir, occasionally on black spruce, and rarely on white spruce, red maple, or white birch. It does not appear to grow directly on bare bark, and is usually found growing in association with the epiphytic liverwort Frullania asagrayana. A healthy, mature specimen of Erioderma pedicellatum can grow at a rate of 11 to 14 mm per year, and populations of this lichen have a generation time of about 30 years. The Scytonema cyanobacteria photobiont of this lichen make it particularly sensitive to acid rain and other atmospheric pollutants. It requires relatively cool and moist oceanic climates and an open canopy, and it deteriorates rapidly on dead trees, or if habitat succession occurs that reduces or increases light availability. Altered microclimatic conditions caused by extensive logging nearby to the lichen also cause it to deteriorate. Old growth balsam fir forests in wet areas of eastern Canada regenerate by gap replacement, which creates a mosaic of forest stands of different ages while maintaining a full or partial canopy for millennia. As a result, these forests can support a unique biota, including Erioderma pedicellatum. It appears that this mosaic of forest stands of different ages is necessary for a viable population of E. pedicellatum. Natural dispersal of E. pedicellatum is evidently possible within these old-growth forests, but there are no known examples of E. pedicellatum establishing in stands previously clear-cut. Erioderma pedicellatum, like all lichens, is a symbiosis, in this instance between an ascomycete fungus and cyanobacteria of the genus Scytonema, and is therefore capable of fixing nitrogen. This symbiotic organism may also be part of second symbiosis with the epiphytic liverwort Frullania asagrayana. The symbiosis between the free-living Scytonema and the germinating ascomycete spores of Erioderma pedicellatum is hypothesized to begin within the water sacs of Frullania asagrayana, where the fungal hyphae assimilates a cyanobacterium, and needs to develop for 5 to 10 years before it reaches a visible size. The liverwort may also benefit from the nitrogen that is being fixed by the cyanolichen growing within it. This complex relationship means that the ecological balance between Erioderma pedicellatum and its cyanobacterial symbiont (Scytonema), its host tree, and (potentially) its liverwort nursemaid (Frullania asagrayana), is very delicate and easily impacted by logging, air pollution, and other factors.