A closer view of this same specimen is below; click to enlarge further.
Or is it Peltigera aphthosa? Only by peeking underneath can you be sure! This post was published as a lichen profile in the Winter 2013 issue of Aquilegia, newsletter of the Colorado Native Plant Society (Vol 37, No. 6). Back issues are available online at the CoNPS website..
Peltigera leucophlebia, Peltigera aphthosa
To distinguish these two species, you’ll probably have to take a peek at the underside. P. leucophlebia, as its name implies, has distinct veins that change from light colored near the margin to black toward the center. Carefully loosen the lichen from the soil or mosses to check for this. In P. aphthosa, the veins tend to be broad and undefined. The uplifted lobes bearing brownish apothecia have, in P. aphthosa, green cortex on the underside of these reproductive structures, but in P. leucophlebia, the cortex is absent or present only as green specks on the white background.
Fun fact: Round dark structures on the upper surface, called cephalodia, contain cyanobacteria, giving these lichens claim to a three-kingdom symbiosis.
Don’t be fooled: Species of Sticta look like Peltigera and are in the same family, but the underside is black with white spots instead of the characteristic veins. Our third green Peltigera, P. venosa, is smaller (less than 2 cm diameter) and each fan-shaped thallus consists of a single lobe, usually with black marginal apothecia.
Several of us took a field trip yesterday to look at lichens and specifically to find lichens that were especially interesting and unusual. We succeeded completely! In our group was a new member of the Native Plant Society who had an interest in learning more about and photographing lichens, mosses, and other often overlooked small beings that we find in nature. His interest and talent have me spending time with the books again, refreshing all the things I used to know and picking up a few new ones in the process. He’s also promised to share his photos on this website soon.
Right before a sad mishap with my brand new camera, I caught this picture:
This lovely Peltigera aphthosa (or maybe P. leucophlebia) was not the most exciting lichen we saw all day, but it was the best, and pretty much the only, photo I captured. Being out looking at lichens means hope for an updated website here, but having a new photographer on board brings the certainty of MUCH better pictures! Stay tuned…