Cladonia / Erioderma / Porina / Pyrenula

Key to the lichen genus Erioderma on La Réunion
by Harrie J. M. Sipman, May 2011

1a Soredia present, marginal - - - 2
1b Soredia absent - - - 3

2a (1) Rhizohyphae spread over much of the lower surface, pale to dark brown - - - E. mollissimum (Samp.) Du Rietz
2b Rhizohyphae restricted to small, mostly marginal tufts, white to bluish black - - - E. sorediatum D.J. Galloway & P.M. Jørg.

3a (1) Rhizohyphae spread over much of the lower surface - - - 4
3b Rhizohyphae restricted to small, mostly marginal tufts, white or black - - - 5

4a (3) Apothecia with prominent, coarsely tomentose margin (hairs c. 0.5 mm long), 1-4 mm wide - - - E. papyraceum P.M. Jørg. & Arv.
4b Apothecia with thin, finely tomentose margin (hairs about 0.2 mm long), 1-2 mm wide - - - E. meiocarpum Nyl.

5a (3) Apothecium margin finely tomentose (hairs c. 0.2 mm long); apothecia strongly constricted at base, directly attached to the thallus - - - 6
5b Apothecium margin spinulose (tomentum hairs strongly conglutinated in c. 0.3 mm long, spine-like bundles); apothecia weakly constricted at base, on top of hoof-like, subcylindrical, 2-3 mm wide thallus extensions - - - E. unguigerum (Bory) Nyl.

6a (5) Thallus veined on lower side - - - E. groendahlianum (Ach.) Vain.
6b Thallus not veined on lower side - - - 7

7a (6) Apothecium margin biatorine; thallus caespitose with many imbricate central lobes, often browned - - - E. borbonica P.M. Jørg. & Van den Boom
7b Apothecium margin lecanorine; thallus foliose with less lobulate center, always grey - - - E. leylandii (Taylor) Müll. Arg.

Relevant references:

Jørgensen, P. M. 2001. The lichen genus Erioderma (Pannariaceae) in China and Japan. Annales Botanici Fennici 38: 259-264.

Jørgensen, P. M. & Arvidsson, L. 2002. The lichen genus Erioderma (Pannariaceae) in Ecuador and neighbouring countries. Nordic Journal of Botany 22: 87-114.

Swinscow, T. D. V. & Krog, H. 1988. Macrolichens of East Africa. British Museum (Natural History), London. 390 pp.

Jørgensen, P. M., van den Boom, P. P. G., Sérusiaux, E. 2009. Notes on the lichen genus Erioderma in La Réunion. Cryptogamie, Mycologie 30 (3): 263-268.