Peltula bolanderi (Tuck.) Wetmore
Bolander's Peltula Lichen
Basis for Listing
Peltula bolanderi (Bolander’s peltula lichen) occurs in arid regions of North America, South America, and Australia (Nash et al. 2001). In North America, the distribution of this species centers in the Sonoran Desert region of the southwestern United States, where it is apparently abundant. Elsewhere in its North American range, P. bolanderi occurs at scattered and often isolated localities.
Peltula bolanderi was unknown in Minnesota until 1994, when a population was documented in Lake of the Woods County (Agassiz Lowlands Subsection). Since this original detection, only one additional population of P. bolanderi has been documented in the state despite extensive searches (Chisago County, Mille Lacs Uplands Subsection), indicating that it is a rare species in our area; hence, it was listed as a species of special concern in 2013.
Peltula bolanderi is a peltate or shield-shaped lichen, with a brown thallus (lichen body). Individual thalli of P. bolanderi are small, often less than 2 mm (0.08 in.) in diameter, though the Minnesota population has broader thalli that are closer to 4-5 mm (0.16-0.20 in.) in diameter. The edges of the thallus of this species undulate and often form distinct lobes, the margins of which are covered with dark-colored soredia (powdery granules of algae and fungus). Peltula bolanderi is typically sterile, and apothecia (disk-shaped fruiting bodies) are very rare. This species is inconspicuous where it occurs and can be easily overlooked, because it often blends in with the rock on which it grows. In Minnesota, there are a number of small brown lichen species that may appear superficially similar to P. bolanderi. This includes two additional species of Peltula: P. patellata and P. euploca. Peltula patellata appears similar to P. bolanderi but lacks soredia, individual thalli are often fertile, and apothecia are usually present. Peltula euploca is extremely similar to P. bolanderi. However, in P. euploca, the margins of the thallus are not strongly undulate, where those of P. bolanderi are (Büdel et al. 2001). Also, it is extremely rare that the thalli of P. euploca are lobed, whereas lobes are regular on thalli of P. bolanderi (Wetmore 2005). In addition to members of the genus Peltula, the closely related Heppia lutosa (heppia lichen) is similar in appearance, but it is typically fertile and grows on the ground over soil rather than on rock, as P. bolanderi does. Endocarpon pusillum (chalice lichen) is another small brown lichen that may resemble members of the genus Peltula. However, E. pusillum is usually fertile, and instead of apothecia, it has perithecia, which are flask-shaped fruiting structures sunken into the lichen thallus. In Endocarpon pusillum, the perithecia appear as small dark-colored dots on the upper surface of the lichen thallus, these structures are not present in P. bolanderi.
Over most of its range, P. bolanderi grows on rocks in arid or desert environments. In North America, the range of P. bolanderi is centered in the southwestern United States, where the species is generally found growing on sheltered portions of non-calcareous rocks and rarely occurs on calcareous substrates (Büdel et al. 2001). Because P. bolanderi has only been collected twice in Minnesota, it is hard to draw conclusions about its habitat in the state. The Lake of the Woods County population is located on cliffs above a river as well as the rock outcrops directly adjacent to the cliffs. The area in which P. bolanderi is located is open, with a western exposure. The adjacent forest is dominated by Quercus macrocarpa (bur oak), Fraxinus nigra (black ash), Betula papyrifera (paper birch), and Populus balsamifera (balsam poplar). The Chisago County population is from an east-facing rock outcrop directly adjacent to the St. Croix River. Both of these populations likely receive high humidity from their respective rivers and both are in fairly exposed localities, unsheltered from sun exposure at various times of day. Although this species has only been recorded from cliff and rock outcrop communities (Laurentian Mixed Forest Province), it is quite possible, if not likely, that it may be overlooked in the state’s prairies (Eastern Broadleaf Forest and Prairie Parkland provinces), where habitat characteristics are similar to those found throughout the species southwestern range. In this region, the species should be searched for on rock outcrops and erratic boulders.
Biology / Life History
Since apothecia are extremely rare on thalli of P. bolanderi, it is likely that most reproduction of this species is asexual and depends on the dispersal of soredia. Soredia can be dispersed by wind, water, animal, or insect. If they are deposited in a favorable habitat, a new lichen thallus can grow from the soredia. Because this species does produce apothecia, albeit rarely, there is some dependence on sexual reproduction through the production of spores. Once a spore has landed in a suitable area, it must find a specific algal partner in order for a thallus to form. It is also possible that P. bolanderi reproduces asexually by fragmenting and dissemination by wind, animal, water, etc.
Conservation / Management
At this time, so little is known about P. bolanderi in Minnesota, it is difficult to determine specific threats or management practices.
Best Time to Search
Peltula bolanderi can be observed year-round, whenever lichens are not covered by snow or ice.
References and Additional Information
Budel, B., and T. H. Nash. 2001. Peltula. Pages 331-340 in T. H. Nash, B. D. Ryan, C. Greis, and F. Bungatrz, editors. Lichen flora of the Greater Sonoran Desert Region. Volume 1. Lichens Unlimited, Tempe, Arizona. 532 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.