Tree moss

Pseudevernia furfuracea is associated with photobionts from the green algae genus Trebouxia. It reproduces asexually by isidia. The ontogeny of isidia development and its role in CO2 gas exchange in P. furfuracea has been investigated. The preferred growing surfaces for P. furfuracea are the so-called "nutrient poor" bark trees, including birch, pine and spruce. The species has two morphologically identical varieties that are distinguished by the secondary metabolites they produce: var. ceratea Zopf. produces olivetoric acid and other physodic acids, while var. furfuracea produces physodic but not olivetoric acid. Some authors (e.g., Hale 1968) have separated the chemotypes at the species level, designating the olivetoric acid-containing specimens as Pseudevernia olivetorina, but more recent literature separates them at the varietal level.