Cladonia / Erioderma / Porina / Pyrenula

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

A. Corticolous and bryophilous species / B. Foliicolous species / C. Saxicolous species

1a Thallus with isidia; perithecia up to 0.6 mm, in thallus-dominated verrucae; ascospores 50-65 x 8-9 μm, 7-septate - - - aff. P. conspersa Malme
1b Thallus without isidia - - - 2

2a (1) Ascospores muriform, 100-125 x 23-25 μm; perispore sometimes present; perithecial verrucae 0.5–1 mm diam. - - - P. farinosa Knight
2b Ascospores with transverse septa only - - - 3

3a (2) Perithecia immersed in the thallus or in thallus-dominated verrucae - - - 4
3b Perithecia not immersed in the thallus or in thallus-dominated verrucae, semi-immersed to superficial, reddish-brown, dark brown or black - - - 8

4a (3) Ascospores 3-4(-5)-septate, 18-22 x 2.5-3 μm; perithecia c. 0.3 mm; corticolous on bryophytes - - - aff. P. bryophila P.M. McCarthy & Kantvilas
4b Ascospores 7- or more septate - - - 5

5a (4) Most or all ascospores 7-septate, mostly 40-50 x 9-10 μm - - - P. nucula Ach.
5b Ascospores with 7 or more septa, over 50 μm long - - - 6

6a (5) Ascospores 80–122 x 3-4 μm; perithecial verrucae up to 0.5 mm diam. - - - aff. P. bellendenica Müll. Arg.
6b Ascospores 8-14 μm wide - - - 7

7a (6) Ascospores 60-90 x 9-11 μm, 8-11–septate - - - P. internigrans (Nyl.) Müll. Arg.
7b Ascospores 80-120 x (8-)10-12(-14) μm, (7–)9–15-septate - - - aff. P. internigrans (Nyl.) Müll. Arg.

8a (3) Perithecia black, c. 0.25 mm diam.; ascospores 3-septate, 17-20 x 3.3-3.6 μm - - - P. aenea (Wallr.) Zahlbr.
8b Perithecia reddish brown; ascospores 3-7-septate - - - 9

9a (8) Ascospores 17–30 Χ 2.5–5 μm, 3-septate; perithecia 0.1–0.2 mm diam. - - - P. leptalea (Durieu & Mont.) A.L. Sm.
9b Ascospores 25–45 Χ 2.5–3 μm, 5-7 septate; perithecia 0.15–0.35 mm diam. - - - P. decrescens P.M. McCarthy & Kantvilas

A. Corticolous and bryophilous species / B. Foliicolous species / C. Saxicolous species

1a Ascospores 3-septate - - - 2
1b Ascospores more than 3-septate - - - 3

2a (1) Ascospores 23-25 x 4-5.5 μm; perithecial verrucae 0.2–0.3 mm diam. - - - P. albicera (Kremp.) Overeem
2b Ascospores 17-26 x 2.5-4.5 μm; perithecia convex, 0.15-0.26 mm - - - P. rufula (Kremp.) Vain.

3a (1) Ascospores 5-6-septate, 20–32 Χ 3.5–6 μm; perithecia tomentose, 0.15–0.25 mm diam. - - - P. nitidula Müll. Arg.
3b Ascospores 7-8-septate - - - 4

4a (3) Ascospores 7-septate, oblong, 37–52 x 4.5-6 μm; perithecial verrucae 0.4-0.5 mm diam. - - - P. lucida R. Sant.
4b Ascospores 7-8-septate, perithecia smaller - - - 5

5a (4) Ascospores 25–35 Χ 3–4.5 μm; perithecial verrucae 0.25–0.4(–0.5) mm diam. - - - P. epiphylla (Fιe) Fιe
5b Ascospores 22-42 x 3.5-7 μm; perithecia ± globose, 0.15-0.3 mm - - - P. atrocoerulea Müll. Arg.

A. Corticolous and bryophilous species / B. Foliicolous species / C. Saxicolous species

1a Ascospores submuriform - - - P. sagedioides (Zahlbr.) P.M. McCarthy
1b Ascospores with transverse septa only - - - 2

2a (1) Perithecia immersed in the thallus or in thallus-dominated verrucae - - - 3
2b Perithecia semi-immersed in thallus-dominated verrucae, orange, orange-brown; ascospores 5-6-septate - - - aff. P. cataractarum Aptroot & Sipman

3a (2) Most or all ascospores 6-7-septate, spores c. 35 μm long - - - 4
3b Ascospores with 7 or more septa, spores longer - - - 5

4a (3) Ascospores 35-36 x 6-7 μm; perithecial verrucae 0.4 mm - - - P. heterocarpa P.M. McCarthy
4b Ascospores 24–44 Χ 3.5–7 μm; perithecial verrucae 0.6 mm - - - P. tetracerae (Afz. in Ach.) Müll. Arg.

5a (3) Perithecial verrucae 0.25–0.5 mm diam. - - - 6
5b Perithecial verrucae 0.5–1.1 mm diam. - - - aff. P. guaranitica Malme

6a (5) Ascospores over 5 μm wide - - - 7
6b Ascospores 35–66 Χ 3.5–5 μm, 7–8-septate - - - P. riparia P.M. McCarthy

7a (6) Ascospores 30-35 x 8 μm, 7-septate - - - P. mastoidea (Ach.) Müll. Arg.
7b Ascospores 50-60 x 9-10 μm, 9-12-septate - - - aff. P. guaranitica Malme

Relevant references:

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