About Peltigera aphthosa (L.) Willd.
Peltigera aphthosa (L.) Willd. is a species of lichen with the common names green dog lichen, leafy lichen, felt lichen, and common freckle pelt. It has a circumpolar distribution, occurring across the Arctic, boreal, and temperate regions of the Northern Hemisphere. This lichen forms a large thallus that can exceed one meter in width, divided into lobes that reach up to approximately 10 centimeters long and 6 centimeters wide. Its thallus is green when moist, and fades to pale when it dries out. The surface of the thallus is dotted with cephalodia, which hold one of the lichen’s two symbionts: a species of Nostoc. The second symbiont is a species of Coccomyxa. Both symbionts carry out photosynthesis, and the Nostoc also fixes nitrogen. The lichen produces large apothecia, which are its reproductive structures. This widespread lichen grows across many habitat types, including Arctic ecosystems. In the southern portions of its distribution range, it grows in alpine climates. This lichen was recorded absorbing aluminum and silicon from ash released by the 1980 eruption of Mount St. Helens. It is a known host for the lichenicolous fungus species Lichenopeltella santessonii.
