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Lichens A-Pac (2007) - Flora of New Zealand Lichens - Revised Second Edition A-Pac
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Arthothelium A.Massal.

ARTHOTHELIUM A.Massal., 1852

Type : Arthonia spectabilis Flot. [=Arthothelium spectabile (Flot.) A.Massal.]

Description : Flora (1985: 17–18).

Key

1
Ascospores 8 per ascus
2
Ascospores 2 per ascus; 30–40 × 12–20 μm
stirtianum
2
Ascospores muriform; end cell not undivided
3
Ascospores with a muriform tail and an expanded, undivided end cell
7
3
Apothecia black or brown-black; K−
4
Apothecia pale red-brown to yellow-brown; K+ purple; ascospores with (4–)7–10 transverse septa and 1–5 vertical septa, 33–46 × 13–25 μm
spadiceum
4
Hymenium colourless to olive or brownish
5
Hymenium bright orange-yellow; ascospores with 4–6 transverse septa and 1–3 vertical septa, 29–36 × 13–16.5 μm
endoaurantiacum
5
Apothecia > 0.4 mm diam., not white-pruinose
6
Apothecia minute, 0.1–0.3 mm diam., coarsely white-pruinose; ascospores with (3–)7–9 transverse septa and 1–3 vertical septa, 20–33 × 13–16.5 μm
suffusum
6
Apothecia dark red-brown to black, to 1 mm diam; ascospores brown at maturity with 5–7 transverse septa and 1–3 vertical septa; 25–30 × 11–14 μm
fusconigrum
Apothecia brown-black to black, 0.4–0.8 mm diam.; ascospores colourless with 4–9 transverse septa and 1–4 vertical septa, 22–33(–40) × 7–12(–14) μm
interveniens
7
Apothecia rounded to oblong; ascospores >30 μm long
8
Apothecia effigurate-branched; ascospores (20–)22–25 × 8–10 μm
pellucidum
8
Apothecia to 1 mm diam; ascospores 30–37(–42) × 10–15 μm
ampliatum
Apothecia 0.3–0.5 mm diam.; ascospores 29–36 × 13–16.5 μm
obtusulum

Arthothelium is a cosmopolitan genus of c. 80 species included in the family Arthoniaceae (Tehler 1990; Eriksson et al. 2004; Pennycook & Galloway 2004; Eriksson 2005). It is characterised by: a crustose, smooth, effuse or verrucose, mostly ecorticate thallus which may be corticolous, foliicolous or saxicolous; rounded, irregular to lirelline, branched, immarginate apothecia-like ascomata having a "rubbed-down" appearance; branching, anastomosing coherent paraphysoids forming a thick epithecium above – outermost paraphysoids often darkening and forming a pseudoparathecium; asci Arthonia -type (Malcolm & Galloway 1997: 186), 8-spored, and subglobose, pyriform, rarely clavate or ellipsoidal, bitunicate, fissitunicate or semi-fissitunicate and thick-walled; and colourless, muriform or transversely septate, ovate to ellipsoidal ascospores, often with an expanded terminal cell and a muriform to transversely septate "tail". Recent accounts of the genus include: Kantvilas (1990c) and Kantvilas & Vězda (1992) for Australian taxa; Coppins & James (1979a) and Coppins (1992c) for British species; Makhija & Patwardhan (1995b) for Indian taxa and Grube & Giralt (1996) for western Mediterranean species. Recently, Makhija & Patwardhan (1995a) described a new species from New Zealand. The foliicolous species, A. vermiferum Zahlbr. (Zahlbruckner et al. 1928: 310–311), described from living leaves of Metrosideros colensoi from Kitchener Park, Feilding, is non-lichenised and is referable to Chaetothyrium (Matzer 1996).

Present indications from both anatomical and molecular studies are that Arthothelium as currently circumscribed is heterogeneous (Tehler 1990; Grube & Giralt 1996; Sundin & Tehler 1998) but no decisions on redefining component genera within Arthothelium s. lat. have been taken until a wider spectrum of material (especially from tropical regions and the Southern Hemisphere) is examined. In this account nine species are recorded, but the genus is largely overlooked and very poorly collected and understood here.

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