Green Reindeer Lichen

The lichen is composed of two thalli; an initial primary squamulose thallus growing across bark in a scaly, flaking pattern, followed by a secondary fruticose thallus (podetium), with cup shaped podetia (4–10 cm tall) bearing terminal ascocarps contained in apothecial structures. The coloring of C. arbuscula varies between subspecies, but is primarily white-gray, pale yellow, or bright green, with darker orange tips where ascocarps are formed. The thallus shows negative results in typical K-tests with no color change.

C. arbuscula is found throughout the world, tolerating harsh conditions that many vegetative plants cannot. It is widely spread in Canada and the Northern United States (mostly Alaska), but also found in Wyoming, Idaho, and Montana. Although it is relatively uncommon in the Pacific Northwest, it can be found there. Common in Labrador and Newfoundland and found throughout England and Ireland. It has been found in more southern latitudes such as Chile, Tasmania, and New Zealand as well, but is most dominant in northern latitudes. The lichen is considered to be secure in terms of conservation, but in some subspecies there are areas of concern in which the species is declining.

C. arbuscula can reproduce both asexually and sexually. The asexual reproduction process can occur through fragmentation of the primary thallus in which a small portion of the thallus can regenerate a fully productive new thallus as long as the original portion contains both algal and fungal cells. Asexual spores known as conidia are produced on pycnidia borne at the edges of the podetia cups and are used to reproduce asexually via fragmentation. Due to the microscopic nature of these asexual reproductive elements, not many studies have been done to describe the in depth reproduction of C. arbuscula.