Peltigera venosa (L.) Hoffm.
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Basis for Listing
Peltigera venosa occurs in the boreal zone (Hale 1979) from southern Alaska south to northern California, and south in the Rocky Mountains to New Mexico in the western part of the continent. In eastern North America, it occurs from Minnesota east to Newfoundland and Labrador, Canada and south to Pennsylvania. In Minnesota, it has only been found in Cook County, where it grows on soil and on moist cliffs. In 1897, Bruce Fink found the species at two localities (Fink 1910), but the only recent collections are from 1977 and 1981. Thorough searches at many localities have yielded no additional records, but some potential habitat remains to be searched. Peltigera venosa was listed as a special concern species in Minnesota in 1996.
A foliose lichen, the thallus (lichen body) of P. venosa appears dull green to light brown when dry, and bright green when wet. Lobes are small, with the lower surface basically white but with broad, dark, raised veins radiating from the base of each lobe in a striking pattern. In mature specimens, apothecia (fruiting bodies) can be found on the lobe tips, and they are black when dry and reddish-brown when wet. The fan-shaped lobes, round apoethecia, and conspicuous black veins distinguish this very small Peltigera from other species (Brodo et al. 2001). This lichen has no positive reactions to chemical tests and does not exhibit fluorescence when exposed to ultraviolet light (Wetmore 1981).
The preferred substrate for P. venosa is rich, not-recently-disturbed soil and mossy rocks. It prefers cool, shady, moist locations, but only where there is little competition from other plants.
Biology / Life History
Peltigera venosa reproduces through the distribution of spores from the fruiting bodies by wind, water, or insects. 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. When active, this lichen is a nitrogen-fixer, contributing to the natural process of nitrogen cycling.
Conservation / Management
Peltigera venosa prefers areas that retain some moisture, so any changes in the forest canopy through harvesting or other forest management activities could negatively affect this lichen. Similar to other lichens, fire would eliminate local populations of this species quickly. Stream and trail developments could also threaten this lichen.
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.