File:A lichen - Cladonia portentosa - geograph.org.uk - 1060979.jpg

English: A lichen - Cladonia portentosa. In a quick examination (undertaken out of curiosity) of a few square metres of the moor for branching, mat-forming Cladonia species, I came upon three such species. One is shown here; for the other two, see: 1060980 and 1060981.

Their presence can reveal certain aspects of their environment; as the introduction to one work notes: "Cladonia is an extensive and difficult genus of lichens, but one that is extremely valuable in defining many plant communities, particularly heathlands" [N.G.Hodgetts, in "Cladonia: a field guide"].

Not all Cladonia species form such mats; for example, other species in this genus form fruiting bodies that look like little golf-tees (the so-called "pixie-cup lichens") or like matchsticks topped with a red spore-mass.

These fruiting bodies are called podetia, and can be thought of as corresponding to the familiar spore-producing discs of other lichens, but with greatly extended vertical growth.

Of the Cladonia species whose podetia form branching mats, C. portentosa, shown here, is extremely common. It branches at a wide angle, and has a very distinctive appearance, with its mats often forming globular heads. The resulting tumbleweed-like shape has certain advantages: "the podetia of richly-branched species of Cladonia commonly become fragmented when dry and brittle, then roll about in the wind until a suitable anchorage is found" [Jack R. Laundon, in "Lichens" (Shire Natural History)].

This species is very common on heaths, dunes, and peat moors, although it is apparently on the decline in many areas [Frank S. Dobson, in "Lichens - An Illustrated Guide to the British and Irish Species"; incidentally, this is the species shown on the front cover of the 5th edition].