Flora of New Zealand Series

≡Leptogium azureum, sensu D.J.Galloway (1985a: 250) nonL. azureum (Sw.) Mont. s. str.

Lectotype: New Zealand. Pohangina near Palmerston North, on Melicytus ramiflorus, H.H. Allan W 29 – CHR 264104 [fide Galloway (1999: 320)].

Description : Thallus submonophyllous to polyphyllous, dark grey-blue to distinctly bluish when wet, dark leaden grey or slate-grey when dry, 2–10 cm diam., attached to substratum by scattered tufts of hairs, loosely attached, corticolous, muscicolous. Lobes rather papery, orbicular to elongate, apices rounded, 2–8(–15) mm broad, margins sinuous, entire to sublobulate. Upper surface smooth to somewhat roughened, never wrinkled–plicate, without isidia or phyllidia. Lower surface concolorous with upper surface, without tomentum. Apothecia common, often abundant, to widely scattered, or occasionally absent, sessile to shortly pedicellate, laminal, 0.2–1.0(–2) mm diam., disc concave to plane or subconvex, pale orange-brown to red-brown, matt, proper exciple rarely seen, thalline exciple entire, thin or with occasional small, microphylline outgrowths, concolorous with thallus or paler, often creamish white. Epithecium orange or yellow-brown, 12.5–15 μm thick. Hymenium colourless, 90–115 μm tall. Hypothecium opaque, pale brownish. Ascospores broadly ellipsoidal, apices distinctly pointed, submuriform, with 3–7 transverse septa and 1–3 longitudinal septa, not constricted at septa, (20–)25–27.5(–32.5) × 10–12.5(–15) μm [Zahlbruckner (1941: 270) gives 20–24 × 5.5–7 μm].

N: Northland (Kaipara) to Wellington (Kaitoke). S: Marlborough (Onamalutu) to Southland (Dusky Sound, Riverton). St: (Glory Cove). C: Rather rare, mainly in wetter western areas where it grows among mosses on trunks and branches of trees and shrubs, also rarely foliicolous, and on mossy rocks in grassland, both E and W of the Main Divide, s.l. to 1000 m (map in Galloway 1999: 322, fig. 1).

?Endemic

Leptogium aucklandicum is characterised by: the corticolous habit; the distinctive blue to blue-grey colour, the large, rather thin lobes with entire, undulate margins, the absence of isidia, and of tomentum on the lower surface. As Verdon (1992a: 178) records "... Many past and recent determinations of L. azureum from south-eastern Australia and N.Z. are misdeterminations of Collema subconveniens (blue-grey form)...", and care is needed to distinguish this Collema from specimens of L. aucklandicum. Young apothecia of C. subconveniens are commonly clustered together in ±erumpent groups, the thalline margins only slightly raised above the level of the thallus. The spores of C. subconveniens are longer, 20–40(–43) μm (and more noticeably apiculate at the apices), and also broader, 8–10.5(–15) μm, and are distinctively constricted at the transverse septa than are those of L. aucklandicum, and generally have mainly 2 and not 3 longitudinal septa for each transverse septum (Degelius 1974: 137).

Although Zahlbruckner recorded both Leptogium tremelloides (L.f.) S.F.Gray, and described L. aucklandica (Zahlbruckner 1941: 270) for broad–lobed, bluish coloured, fertile, non-isidiate specimens of Leptogium from New Zealand, later accounts (e.g. Galloway 1985a, 1992; Malcolm & Galloway 1997) included this material under the name L. azureum, following the then current rather wide interpretation of this latter name. Jørgensen & James (1983: 116), in a discussion of the "L. azureum" group of taxa in Europe, emphasised the confusion and complications surrounding the nomenclature of these often widely reported taxa, showing that L. tremelloides is an illegitimate name, and introducing a greater precision to the limits of L. azureum. Swartz's type material of Lichen azureus from Jamaica (Acharius 1799) on which the name Leptogium azureum is based, and which is supported by a fine, early, coloured engraving in his own account of his West Indian lichens (Swartz 1811: tab. 21), is shown to have the following characters: bright grey-blue, flat, broadly orbicular lobes, to 5 mm wide and 70–100 μm thick; sessile or shortly stalked apothecia to 2 mm diam., with a narrow margin often excluded at maturity; a proper exciple of periclinal hyphae; and sparingly muriform spores (18–)20–25(–32) × (6–)7–9(–10) μm (Jørgensen & James 1983: 112, tab. 1).

As is shown above and in Zahlbruckner's description, L. aucklandicum has a thicker thallus (170–180 μm thick), and has a duller and darker grey-blue colour, and not the vivid bright grey-blue of typical L. azureum, and the spores are slightly broader. Since the New Zealand material is not quite typical of L. azureum  s. str. from the West Indies and elsewhere (Jørgensen & James 1983; Swinscow & Krog 1988; Aragón et al. 2004), Zahlbruckner's name is revived for the New Zealand material pending further investigations on other Southern Hemisphere populations. Aragón et al. (2004: 346) map the known world distribution of L. azureum and include New Zealand in their data.