Ahtiana aurescens (Tuck.) Thell & Randlane
Eastern Candlewax Lichen
Basis for Listing
Minnesota is one of the few states to have had a fairly thorough study done on lichens at a time when there were still undisturbed forests. Between 1896 and 1910, Bruce Fink collected lichens in many parts of the state and published a series of papers on his findings, which were summarized in one volume (Fink 1910). Fink's collections noted that Ahtiana aurescens was common at sites near Tower and Baudette in St. Louis County. More recently, Dr. Clifford Wetmore has found this lichen in multiple sites in Minnesota's Arrowhead region. Continuing pressure to harvest remaining old-growth forests supports the 1984 designation of this lichen as a state special concern species.
Ahtiana aurescens is a foliose lichen whose thallus (lichen body) is greenish-yellow, with narrow lobes that have wavy margins. Apothecia (disc-shaped fruiting bodies) are uplifted, and occur on the upper surface of the thallus near the lobe margins. The lower surface of the thallus is light-colored, ranging from tan to white (Wetmore 1981).
This lichen species has an Appalachian-Great Lakes distribution pattern. It grows on conifer bark in old forests in the eastern part of its range (Hale 1979). In the Great Lakes region, it is usually restricted to conifer bark in Thuja occidentalis (northern white cedar) swamps. In Minnesota, C. aurescens has been found only in the northernmost tier of counties. This lichen grows on branches and twigs, mainly in areas with fairly dense shade.
Biology / Life History
Ahtiana aurescens reproduces strictly through the dispersal of fungal spores. Once transported, the spores must find the proper algal partner in the suitable environment in order to become established as a new thallus in that location.
Conservation / Management
In some Minnesota locations, C. aurescens was historically common. Damage from certain forms of timber harvesting and the establishment of roads in old-growth coniferous forests continues to be a threat to the survival of this species. In general, any activities that degrade or destroy forested peatlands dominated by old Picea mariana (black spruce) or old T. occidentalis could potentially threaten the survival of C. aurescens, if it occurs there. Allowing the land that exists between older patches of bogs to age would likely improve habitat for this rare lichen species.
Conservation Efforts in Minnesota
Scientists are searching for this and other rare lichens in an attempt to identify and possibly preserve local populations.
References and Additional Information
Brodo, I. M., S. D. Sharnoff, and S. Sharnoff. 2001. Lichens of North America. Yale University Press, New Haven, Connecticut. 795 pp.
Fink, B. 1910. The lichens of Minnesota. Contributions from the United States National Herbarium 14(1):1-250.
Hale, M. E. 1979. How to know the lichens (Pictured Key Nature Series). Second edition. William C. Brown Co., Publishers. Dubuque, Iowa. 246 pp.
U.S. Forest Service. 1999. Population viability assessment in forest plan revision. Statement of purpose and reason. Draft species data records: Cetraria aurescens. United States Forest Service, Region 9.
Wetmore, C. M. 1981 (revised 2005). Keys to the Lichens of Minnesota. Department of Plant Biology, University of Minnesota, St. Paul, Minnesota. 92 pp.
Wetmore, C. M. 2002. Conservation assessment for (Cetraria aurescens) Tuck. United States Forest Service, Eastern Region, Milwaukee, Wisconsin. 13 pp.