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Lichens A-Pac (2007) - Flora of New Zealand Lichens - Revised Second Edition A-Pac
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Coenogonium Ehrenb.

COENOGONIUM Ehrenb., 1820

=DIMERELLA Trevis., 1880

Type : Coenogonium linkii Ehrenb.

Type : Dimerella lutea (Dicks.) Trevis. [=Coenogonium luteum (Dicks.) Kalb & Lücking]

Description : Flora (1985: 131).

Key

1
Thallus corticolous
2
Thallus foliicolous
5
2
Apothecia yellow or yellow-white
3
Apothecia reddish brown or brown
rubrifuscum
3
Apothecia yellow to yellow-orange
4
Apothecia yellowish to whitish, 0.2–0.25 mm diam., margins concolorous with disc; hymenium 40–45 μm tall
lutescens
4
Thallus thin, pale yellow-green to dark-green, continuous or areolate; apothecia orange; ascospores 1-septate, 6–12(–14) × 2–4 μm
luteum
Thallus felt-like, pannose, olive-green to greenish yellow; apothecia carneous-yellow; ascospores 1-septate, 7–12 × 2–4 μm
implexum
5
Apothecia epiphyllous
6
Apothecia hypophyllous, rarely epiphyllous
8
6
Thalli without a marginal prothallus
7
Thalli with a prominent, thick white, marginal prothallus; apothecia 0.25–0.5 mm diam., reddish yellow; hymenium 45–65 μm tall; ascospores 6–12 × 2.5–4(–4.5) μm
zonatum
7
Apothecia 0.2–0.28 mm diam., brick-red; hymenium 60–70 μm tall; ascospores 6–9 × 1.8–2 μm
fuscescens
Apothecia 0.5–0.7 mm diam.; pale yellow-brown; hymenium to 45 μm tall; ascospores 6.5–7.5 × 1.8–2 μm
queenslandicum
8
Thalli with pale-yellow, tubular pycnidia
flavum
Thalli without pycnidia
fallaciosum

Coenogonium is a tropical/subtropical genus of 45–50 species (Santesson 1952; Uyenco 1963; Kalb 2001c; Kirk et al. 2001), included in the monogeneric family Coenogoniaceae (Eriksson et al. 2004; Pennycook & Galloway 2004). It is not possible to identify species of Coenogonium accurately in the absence of apothecia. Recently, Lücking & Kalb (2000: 31–32) synonymised Dimerella and a further seven genera (Byssiplaca A.Massal.,  Biatorinopsis Müll.Arg.,  Microphiale (Stizenb.) Zahlbr.,  Holocoenis Clem.,  Lecaniopsis (Vain.) Zahlbr.,  Didymopycnomyces Cavalc. & A.A.Silva and Flabellomyces Y.Kobayashi) within Coenogonium. The conspecificity of Coenogonium and Dimerella was confirmed in a molecular study (Kauff & Lutzoni 2002) and this view is adopted here. Seaward & Aptroot (2004), however, accept Dimerella as a separate genus, distinguished from Coenogonium by a crustose thallus, 1-septate ascospores (half of the species of Coenogonium have simple ascospores), and often swollen excipular cells. Four species of Dimerella from New Zealand were recently transferred to Coenogonium, in line with current practice (Malcolm 2004, 2005). Nine species are known from New Zealand.

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