Ramalina roesleri (Hochst. ex Schaerer) Hue
Frayed Ramalina Lichen
Basis for Listing
Ramalina roesleri (frayed Ramalina lichen) has a discontinuous range in North America (Brodo et al. 2001). The species occurs on both the Atlantic and Pacific coasts and in scattered areas throughout the arctic and boreal forest. In the Great Lakes area, R. roesleri has been recorded from Isle Royale in Michigan, along the North Shore of Lake Superior in Ontario, and from a small island in Lake Superior in Cook County, Minnesota. Ramalina roesleri was listed as a state species in 2013.
Ramalina roesleri is a fruticose (shrub-like) lichen species that has a greenish-yellow thallus (lichen body), with narrow branches. Members of the genus Ramalina superficially resemble some species of Usnea; they can be readily differentiated by looking for a dense central cord, which runs through the center of Usnea thalli. The thalli of Ramalina species do not contain a central cord.
In Minnesota, R. roesleri can be reliably separated from other species of Ramalina by the following combination of characteristics: the thallus branches are flat in cross-section; hollow, with perforations in the cortex, and have soredia on the tips of the branches (Wetmore 2005). In addition, the thalli of R. roesleri are often compact and shrub-like in general appearance, and the branches are often narrow, less than 1 mm (0.04 in.) in width (Hinds and Hinds 2007).
The habitat for R. roesleri in Minnesota is poorly known. The only collection of the species in the state was from a small island in Lake Superior (North Shore Highlands Subsection). The island is characterized by old-growth fir forests, with abundant lichen and bryophyte cover due to the climate modifying effect of Lake Superior. At this locality, R. roesleri was found growing on the trunk of a mature Sorbus spp. (mountain ash). This locality has not been visited since its discovery in 1980, but it is assumed that R. roesleri persists at this location. Similar habitat exists on the mainland, but as of 2016, no additional specimens have been recorded from the state.
Biology / Life History
Ramalina roesleri reproduces asexually through the dispersal of soredia. Soredia are reproductive structures that contain both fungal and algal partners and can be dispersed over short distances. Apothecia (disk-like fruiting structures of lichens) have been documented on R. roesleri but are extremely rare. Therefore, it is unlikely that sexual reproduction plays a major role in the reproduction and spread of this species.
Conservation / Management
Throughout much of the range of R. roesleri, loss of habitat is the primary threat to its survival. Some forest management practices, mining, housing developments, and heavy recreational activity can negatively alter the habitats where this and other rare lichens occur. Efforts should be made to minimize damage to old-growth forests to protect this and other rare lichen species.
Best Time to Search
Searches for R. roesleri can be conducted year-round, when they are not covered by snow or ice.
Conservation Efforts in Minnesota
The lone site for R. roesleri in Minnesota is on Susie Island in Lake Superior, which is now owned by the Grand Portage Band of Lake Superior Chippewa. Under band control, "human influence on the island will be kept to a minimum in order to protect areas of cultural significance as well as the natural environment".
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.
Hinds, J. W., and P. L. Hinds. 2007. Macrolichens of New England (Memoirs of the New York Botanical Garden, Volume 96.) New York Botanical Garden Press, Bronx, New York. 608 pp.
Minnesota Department of Natural Resources. 2003. Field guide to the native plant communities of Minnesota: the Laurentian mixed forest province. Ecological Land Classification Program, Minnesota County Biological Survey, and Natural Heritage and Nongame Research Program. Minnesota Department of Natural Resources, St. Paul, Minnesota. 352 pp.
Wetmore, C. M. 1981 (revised 2005). Keys to the Lichens of Minnesota. Department of Plant Biology, University of Minnesota, St. Paul, Minnesota. 92 pp.