Steinera lebouvieri Ertz 2017, spec. nov.
Creators: name: Ertz, Damien
name: Poulsen, Roar S.
name: Charrier, Maryvonne
name: Søchting, Ulrik
Publisher: name: Zenodo
Year: 2017
Subjects: Biodiversity
Taxonomy
Fungi
Ascomycota
Lecanoromycetes
Peltigerales
Koerberiaceae
Steinera
Steinera lebouvieri

description: Steinera lebouvieri Ertz spec. nov. (Fig. 6)   
MycoBank: MB 822680  
 Diagnosis: A species of Steinera characterized by a pale greyish to whitish, often with a pinkish tinge, subfoliose to placodioid thallus with central parts remaining subfoliose and marginal lobes (2–)3–5(–6) mm wide, (1–2–)3-septate ascospores that are (17–)19–26(–31) × 7–10 μm.   
 Type:—CROZET. Île de La Possession, Mont du Mischief, tout près du sommet, c. 910 m, 46°24’59”S, 51°41’37”E, sur rochers moussus, 8 December 2015, D. Ertz 20867 (holotype BR!, isotype PC!)   
 Etymology: The new species is dedicated to Marc Lebouvier for his outstanding work on the terrestrial biodiversity of the French subantarctic islands.   
 Thallus subfoliose to placodioid, rather loosely attached to the substrate, 2–3(–4) cm diam., margin distinctly and ±regularly lobate, central parts remaining subfoliose (never crustose); marginal lobes (2–)3–5(–6) mm wide. Upper surface smooth in distal parts, sometimes ±scabrid in central parts, pale greyish to whitish, often with a pinkish tinge, not pruinose, without soredia or isidia. Apothecia abundant, mostly restricted to the central areas of the thallus, discrete or sometimes confluent, up to 0.6(–0.8) mm diam., immersed when young, remaining immersed or becoming sessile, without or rarely with a slightly constricted base at maturity; disc dark brown or reddish-brown to almost black, plane to slightly convex at maturity; thalline margin inconspicuous to narrow at maturity, to 0.12 mm wide, concolourous with thallus. Thalline anatomy: thallus c. 300–700 μm thick; hyphae in upper 1/2–1/3 of thallus running perpendicularly to surface becoming short-celled and densely packed towards upper surface; upper ±algal-free layer consists of a c. 15–50 μm thick, hyaline layer of ±isodiametric cells, 4–8(–10) μm, rarely slightly elongated and then 8–10 × 5–6 μm diam. that is overlaid by a necrotic layer, c. 5–10 μm thick. Photobiont Nostoc; individual photobiont cells 4–8 μm diam., heterocytes 5–8 μm diam.; hyphae in medulla c. 2–4(–5) μm wide. Lower surface light-brown to whitish, in the foliose distal parts of thallus with a ±irregularly developed cortex layer c. 20–25 μm thick, composed of thick-walled, ±isodiametric cells, 3–5 μm diam. Apothecial anatomy: Excipulum compound, consisting of an inner proper exciple and an outer thalline exciple; proper exciple hyaline, becoming brownish near the surface, laterally of hyphae arranged in parallel, 10–25 μm, with cells of c. 5–10 × 2–3 μm and basally paraplectenchymatous, 20–35 μm, with isodiametric c. 4–6 μm diam. to elongate cells up to 15 × 5 μm; thalline exciple inconspicuous or to c. 40–70 μm thick. Hymenium 100–150 μm high; epihymenium pale orange, 10–25 μm; paraphyses branched-anastomosing mainly in upper parts of hymenium, 2–3 μm wide; apical cells swollen, with brown walls, up to 4–5 μm wide, K+ faintly darker brown. Hypothecium 70–180 μm high. Asci 70–90 × 20–25 μm, tholus apparently including a deeper staining KI+ dark blue ring structure; ascospores 8 per ascus, (1–2–)3-septate, straight or slightly curved, narrowly ellipsoid to oblong with rounded to pointed ends, (17–)19–26(–31) × 7–10 μm. Pycnidia not seen.   
 Distribution and ecology: Steinera lebouvieri is known from Crozet and Kerguelen. It is usually found on saxicolous mosses, rarely directly on exposed rock. On Île de La Possession (Crozet), it seems to be restricted to the highest summits where it is locally abundant. On Kerguelen, the species is rare and was observed mainly near waterfalls in Val Studer and near the summit of Mt. Crozier.   
 Notes: Steinera lebouvieri is reminiscent of other species in the genus having a pale greyish to whitish thallus. It is characterized by a combination of the following characters: thallus large, with wide thallus lobes, greyish to whitish and often with a pinkish tinge, and four-celled ascospores. It differs from S. molybdoplaca by the larger thallus’ lobes having a pinkish tinge and while S. molybdoplaca always grows on rock, S. lebouvieri is usually found on saxicolous bryophytes. In Crozet, it was typically found only at high elevation. Henssenia glaucella differs by much smaller thallus and 0(–1)-septate ascospores. Degelia neozelandica (C.W. Dodge) P.M. Jørg. & D.J. Galloway (syn. Steinera neozelandica C.W. Dodge, Parmeliella neozelandica (C.W. Dodge) D.J. Galloway & P. James) differs from the new species notably by simple, much smaller (12–14 × 4–5 μm) ascospores, an arachnoid lower thallus surface and apothecial margin concolorous with the disc or darker (Galloway & James 1984).   
 Additional examined specimens: CROZET. Île de La Possession, Pic du Mascarin, c. 930 m, 46°26’19”S, 51°44’41”E, 6 December 2015, D. Ertz 20826 (BR). KERGUELEN. Péninsule Courbet, Val Studer, vallon encaissé s’ouvrant dans le versant droit de la Rivière du Sud un peu en aval du Lac Supérieur, 105 m, 49°17’27”S, 70°03’11”E, 16 November 2016, D. Ertz 20996 (BR); ibidem, versant droit de la Rivière du Sud un peu en aval du Lac Supérieur, 90 m, 49°17’22”S, 70°02’59”E, 16 November 2016, D. Ertz 20988, 20990 (BR); ibidem, Grande Cascade, c. 800 m SE of Lac Supérieur, 100 m, 49°17’5”S, 70°03’3”E, 18 December 1998, R.S. Poulsen 371 (C); c. 1–1.5 km NE of summit of Mt. Crozier, 49°17’3”S, 69°59’8”E, 18 December 1998, R. S. Poulsen 349 (C).
description: Published as part of Ertz, Damien, Poulsen, Roar S., Charrier, Maryvonne & Søchting, Ulrik, 2017, Taxonomy and phylogeny of the genus Steinera (Arctomiales, Arctomiaceae) in the subantarctic islands of Crozet and Kerguelen, pp. 201-238 in Phytotaxa 324 (3) on pages 213-215, DOI: 10.11646/phytotaxa.324.3.1, http://zenodo.org/record/13698300