Peltigera collina is most often found decorating the bark of trees. It is the most common epiphytic Peltigera, and is in fact the only sorediate Peltigera which is epiphytic on trees.
I really wasn’t expecting to find this species while examining some cliffs near the Little White Salmon River. This specimen was the first one I have found on moss over rock, and the first one with such black apothecia. In fact I’d forgotten they could be so dark, and was rather confused until I dug out my book.
This was a good location for Peltigera, with P. neopolydactyla, P. membranacea, P. canina (which I’ll profile tomorrow, since I’m off to watch the Super Bowl with my Dad and won’t be getting anything else written today), and this P. collina, all represented there.
Description– Light to dark grey or brown foliose thallus which is glabrous (hairless), slightly matte or scabrous, and loosely appressed; abundant marginal soredia (although sometimes lacking soredia in epiphytic specimens); dark brown to black saddle apothecia on thin lobes; ventral veins brown and low; rhizines abundant, bushy or singular.
Similar species–Peltigera didactyla is our only other sorediate species of Peltigera, and it usually has a tomentose dorsal surface, and soredia in the field of the thallus; P. neckeri has blackish apothecia but lacks soredia, has a shinier dorsal surface, has indistinct ventral veins, and is seldom epiphytic; P. venous also has black apothecia, but they are round, and the thallus is bright green; Sticta limbata has some sub marginal soredia, yellowish tan below, and lacks apothecia; Nephroma parile has smooth, tan ventral surface.
Habitat– On bark and mossy bark, and occasionally on moss over rock; damp areas from low elevations to subalpine.
Range-Holarctic; region wide in appropriate habitat.
Eaten by– Like most Peltigera it is eaten by some slugs and snails.
Etymology of names– Peltigera translates from Latin as ‘shield bearer’, and refers to the shape of the thalli in many members of this genus. The specific epithet collina means ‘hills’ in Latin, and refers to the habitat where this species was first found.