Rare Species Guide

 Parmelia stictica   

Rock Speckled Shield Lichen 

MN Status:
Federal Status:


(Mouse over a habitat for definition)

Minnesota range map
Map Interpretation
North American range map
Map Interpretation


Punctelia stictica

  Basis for Listing

Parmelia stictica is rare throughout its range in North America. It is known from the Lake Superior region, Colorado and New Mexico, and the West Coast. In Minnesota, it has been collected only twice: once near Split Rock Lighthouse in Lake County and once near Grand Portage in Cook County. Both locations were along the shore of Lake Superior. Cabin building and other developments along the shore may have destroyed much of this species' habitat. Parmelia stictica was listed as an endangered species in Minnesota in 1984.


Parmelia stictica is a foliose (leaflike) lichen. The thallus (lichen body) is gray with brown lobe ends and numerous white pores on the upper surface that develop into sorediate isidia (granular, fingerlike projections on the upper surface of the thallus). Thallus lobes are over 5 mm (0.2 in.) wide, without cilia (hairs) on margins. The lower surface of the thallus is dark brown to black, with rhizines (rootlike structures). The thallus medulla (middle layer) turns red when subjected to bleach as a chemical spot test. Parmelia stictica contains green algae (Wetmore 1981).

Parmelia sulcata is a similar lichen, but it has white lines on the upper surface of the thallus. Parmelia bolliana is also similar with white dots on the upper surface but distinct in lacking soredia.


Parmelia stictica grows on rocks along the shore of Lake Superior. In other parts of its range, it grows on north-facing cliffs near lakes or on exposed ridgetops in the mountains.

  Biology / Life History

This species reproduces asexually, relying on the dispersal of soredia. Soredia are powdery vegetative structures that contain both fungal and algal components of the lichen. When successfully dispersed to a favorable habitat, the soredia grow into a new lichen thallus.

  Conservation / Management

Loss of habitat is likely the main threat to P. stictica. Residential and recreational development along the shore of Lake Superior may destroy this lichen's habitat, thereby negatively affecting any remaining populations of this extremely rare species.

Searches for P. stictica may be conducted year-round when lichens are not covered by snow or ice.

  Conservation Efforts in Minnesota

This species and other rare lichens are targeted for botanical searches by scientists in an attempt to locate additional occurrences and conserve remaining 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.

Hale, M. E. 1979. How to know the lichens (Pictured Key Nature Series). Second edition. William C. Brown Co., Publishers. Dubuque, Iowa. 246 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.

Back to top