Stereocaulon argus
Synonyms
Stereocaulon argodes, Stereocaulon macrocarpum var. argus
Family
Stereocaulaceae
Flora category
Lichen – Native
Endemic taxon
Yes
Endemic genus
No
Endemic family
No
Structural class
Lichens - Fruticose
Current conservation status
2018 | At Risk – Naturally Uncommon | Qualifiers: RR
Brief description
Characterised by the saxicolous habit; the coarse and strongly rugose to verrucose or areolate cortex; the corticate phyllocladia with smooth, white, glossy tips, finger-like and often restricted to the base of podetia, becoming flattened and coralloid-branched at maturity, also often ridged and cracked; the small, globose cephalodia, 1.5–2(–5) mm diam., smooth or coarsely rugose, sessile or very shortly stalked, grey-white, surface smooth, matt, never areolate or maculate; and the distinctive chemistry (atranorin and perlatolic acid).
Distribution
Stewart Island: (Smith’s Lookout). Campbell Island: (Mt Fizeau, Mt Sorenson, St Col Peak). Auckland Islands. Macquarie Island. Antarctica.
Habitat
On open winsdswept grasslands of the subantarctic islands, on rock outcrops.
Detailed description
Thallus large, robust, 4-7(-10) cm tall, branching ± dichotomous at base becoming sympodial towards apices. Pseudopodetia very firmly attached by a well-developed holdfast, basal or primary branches stout, 1.5-3(-5) mm wide, often decorticate, smooth, to strongly vertically furrowed and cracked, upper parts of branches mostly corticate although the cortex may extend to the base of pseudopodetia. Phyllocladia sparse, corticate, with smooth, white, shining tips, simple, terete, gnarled, finger-like at first and often ± restricted to the base of pseudopodetia, becoming flattened, coralloid-branched at maturity (to 7 mm long) and often ridged and cracked, at the apices of pseudopodetia phyllocladia are smaller and nodular, rounded or flattened. Cephalodia developed on large pseudopodetia, small, globose (1.5-)2-5 mm diam., sessile or very shortly stalked, greyish-white, surface smooth, matt, never areolate or maculate. Apothecia terminal, large (to 5 mm diam.), disc brownish-purple to black, plane in immature fruits and then with a conspicuous pale margin, becoming convex and immarginate at maturity. Hypothecium 75 µm tall, colourless to pale brownish. Asci clavate, 6-8-spored. Ascospores colourless to pale yellowish, 3-7-septate, 30-50 × 4-6 µm.
Chemistry: Atranorin and perlatolic acid, and possibly stenosporic acid and traces of unidentified compounds.
Similar taxa
Stereocaulon argus may be confused with Argopsis megalospora, as the two species are often sympatric and have a similar geographical distribution and habitat preference. S. argus may also be mistaken for some forms of S. ramulosum. However, the cortex of the pseudopodetia, and the structure of the phyllocladia and cephalodia distinguish S. argus (the chemistry of the two species is similar), and when fertile the fruits of the two species are readily separable.
Substrate
Saxicolous
Attribution
Fact sheet prepared by Melissa Hutchison (25 June 2021). Information in the Brief description, Distribution, Habitat, Features and Similar taxa sections copied from Galloway (1985, 2007).
References and further reading
Galloway D.J. 1985: Flora of New Zealand: Lichens. Wellington: PD Hasselberg, Government Printer. 662 pp.
Galloway D.J. 2007: Flora of New Zealand: Lichens, including lichen-forming and lichenicolous fungi. 2nd edition. Lincoln, Manaaki Whenua Press. 2261 pp.