Cladonia / Erioderma / Porina / Pyrenula

Key to the lichen genus Pyrenula on La Réunion
by Pieter P. G. van den Boom, Aug. 2011

1a Ascospores submuriform to muriform - - - 2
1b Ascospores with transverse septa only - - - 5

2a (1) Thallus and/or ascomata with yellow to orange or rust-coloured K+ purple pigments - - - P. ochraceoflava (Nyl.) R.C. Harris
2b Thallus and ascomata without K+ purple pigments - - - 3

3a (2) Ascospores <20 μm long - - - P. parvinuclea (Meyen & Flot.) Aptroot
3b Ascospores >20 μm long - - - 4

4a (3) Ascospores 70-85 x 25-27 μm; ascomata semi-immersed - - - P. aff. pyrenuloides (Mont.) R.C. Harris
4b Ascospores 70-75 x 20-35 μm; ascomata immersed - - - P. aff. neoculata Aptroot

5a (1) Thallus white, evanescent, not corticated - - - P. microcarpa Müll. Arg.
5b Thallus brownish to olive, usually corticated - - - 6

6a (5) Hamathecium densely inspersed with oil droplets - - - 7
6b Hamathecium not or only partly inspersed with oil droplets - - - 8

7a (6) Ascospores 18-20 x 8 μm; perithecia - - - P. massariospora (Starbäck) R.C. Harris
7b Ascospores 15-17 x 10-11 μm; Perithecia to 0.6 mm diam. - - - ?P. subcongruensMüll. Arg.

8a (6) Ascospores with terminal lumina lying directly against the exospore - - - 9
8b Terminal lumina separated from the exospore by an endospore layer - - - 10

9a (8) ascospores 15-18 x 9-10 μm - - - P. nitidula (Bres.) R.C. Harris
9b Ascospores 26-27 x 12-14 μm - - - P. aff. anomala (Ach.) A. Massal.

10a (8) Ascospores 23–38 μm long - - - 11
10b Ascospores mostly < 23 μm long - - - 12

11a (10) Ascospores usually with rounded ends, 25-32 x 10–13 μm; ascomata partly covered by thallus; with white pseudocyphellae - - - P. quassiaecola Fée
11b Ascospores 25-35 x 10-15 μm; ascomata immersed in thallus; without pseudocyphellae - - - P. aff. quassiaecola Fée

12a (10) Ascomata at least partly immersed in the thallus; thallus yellowish to olive green; ascospores 12–20 x 5-7 μm - - - P. dermatodes (Borrer) Schaer.
12b Ascomata semi-immersed, dark olive green; ascospores 20-25 x 7-15 μm - - - P. aff. dermatodes (Borrer) Schaer.

Relevant references:

Australian Biological Resources Study, Checklist of the lichens of Australia and its island territories