Steinera isidiata Ertz & R.S. Poulsen, 2017

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, Phytotaxa 324 (3), pp. 201-238 : 210-212

Steinera isidiata Ertz & R.S. Poulsen spec. nov. ( Fig. 4 )

MycoBank: MB 822678

Diagnosis: A species of Steinera characterized by a subfoliose to placodioid, brown isidiate thallus with marginal lobes 0.5–3 mm wide, (2–)3-septate ascospores that are 18–25(–28) × (5–)6–7 μm.

Type:—CROZET. Île de La Possession, partie amont de la rivière de la Crique de la Chaloupe (nord-ouest de la base Alfred Faure), le long du transit vers la Baie Américaine, c. 125 m, 46°24’40”S, 51°49’58”E, bloc rocheux dans le lit du ruisseau, sur mousses près du niveau de l’eau, 26 November 2015, D. Ertz 20689 (holotype BR!, isotype PC!).

Etymology: The specific epithet refers to the isidiate thallus.

Thallus subfoliose to placodioid, rather loosely attached to the substrate, 1–3(–4) cm diam., margin distinctly and ±regularly lobate; marginal lobes 0.5–3 mm wide. Upper surface smooth, dark-brown, rarely pale brown when less exposed, not pruinose, with scattered to abundant isidia on the upper surface or rarely at the margin of the thallus, sometimes covering the entire surface of the central parts of the thallus; isidia concolorous with the thallus, globose to ± narrowly clavate, sometimes ±spathulate, simple, bifurcate or branched-coralloid, up to 1 × 0.15 mm. Apothecia often absent, but sometimes abundant, mostly restricted to the central areas of the thallus, discrete or sometimes 2–5(–10) contiguous, rarely fused, 0.3–0.8(–1) mm diam., immersed when young, remaining immersed or becoming slightly sessile at maturity; disc red-brown to black, plane to slightly convex at maturity; thalline margin sometimes visible at maturity, narrow, to 60 μm wide, concolourous with thallus. Thalline anatomy: thallus c. 200–400 μm thick; hyphae in upper 1/2–1/3 of thallus running perpendicularly to surface getting short-celled and densely packed towards upper surface; upper ±algal-free layer consists of a c. 15–30 μm thick, hyaline to pale brown layer of ±isodiametric or slightly elongated cells of c. 3–6(–10) × 3–5 μm diam., which is sometimes overlaid by a necrotic layer, 2–4 μm thick. Photobiont Nostoc ; individual photobiont cells 3–7(–10) μm diam., heterocytes c. 6–8 μm diam.; hyphae in medulla c. 2–4(–5) μm wide. Lower surface light-brown to whitish, smooth, with a ±irregularly developed hyaline cortical layer c. 15–20 μm thick, composed of irregularly shaped, ±isodiametric or slightly elongated cells of c. 3–6(–10) × 3–5 μm diam.; rhizines few, short, simple, concolorous with the thallus. Apothecial anatomy: Excipulum 30–60 μm thick consisting laterally of short-celled, c. 12–15 × 4–6 μm hyaline hyphae arranged in parallel and becoming brownish near the surface, and basally paraplectenchymatous, of hyaline cells c. 4–7 μm diam. Hymenium 90–120 μm high; epihymenium brown; paraphyses branched-anastomosing mainly in upper parts of hymenium, 2–3 μm wide; apical cells shortened and swollen, with brown walls, 3–4 μm wide. Hypothecium 75–150 μm high. Asci 70–75 × 14–20 μm, tholus with a KI+ dark blue outer layer; ascospores 8 per ascus, (2–)3-septate, straight, narrowly ellipsoid to fusiform with usually pointed ends, 18–25(–28) × (5–)6–7 μm. Pycnidia not seen.

Distribution and ecology: This species is mainly restricted to lowland habitats but also occurs in higher elevation. It is primarily found on various saxicolous mosses, but has also been seen on gravelly soil, and occasionally directly on basaltic rock. It is scattered to relatively common throughout all investigated areas on Crozet and Kerguelen, with well-developed thalli near streams.

Notes: Steinera isidiata is similar to S. latispora that differs by a non-isidiate thallus, ascospores having sometimes a longitudinal septum and being slightly shorter and wider, 16–20 × 7–8 μm ( Øvstedal & Gremmen 2006). Steinera isidiata is also reminiscent and phylogenetically close to S. subantarctica but that species differs by a non-isidiate, smaller thallus and 5–6-septate ascospores 28–32 × 4–5 μm ( Øvstedal & Gremmen 2001, sub. ‘ Arctomia ’ subantarctica ). Steinera olechiana also has a brown isidiate thallus but differs by 5–7-septate ascospores that are 34–42 × 5–8 μm ( Alstrup & Søchting 2011). Earlier reports of the superficially similar Massalongia carnosa (Dicks.) Körb. (1855:109) from the subantarctic and antarctic should be checked against this species, despite its presence in the southern hemisphere is at least confirmed for the Falklands (A. Fryday pers. comm.). They differ e.g. in internal thallus anatomy and characters of the apothecium including spore septation (1-septate in M. carnosa ). Specimen Ertz 20816 growing on acrocarpous mosses is almost entirely isidiate, with very reduced thallus lobes, looking almost as a tiny fruticose-coralloid lichen. A lichenicolous fungus (black perithecia immersed in the thallus) is present on specimen Ertz 20816.

Examined specimens: CROZET. Île de La Possession, Pointe Basse, rivière juste en amont de l’arbec, c. 80 m, 46°21’56”S, 51°42’40”E, blocs rocheux sur la berge d’un ruisseau, sur mousses près du niveau de l’eau, 30 November 2015, D. Ertz 20713 (BR); ibidem, Arête des Djinns, c. 700–900 m, 46°26’07”S, 51°46’48”E, rocher de crête, sur mousses, 06 December 2015, D. Ertz 20816 (BR); Mont du Mischief, col situé juste au nord-est du sommet, entre la vallée des Géants et le vallon situé au nord du sommet du Mischief, c. 795 m, 46°24’46”S, 51°41’47”E, gros bloc rocheux, sur mousses, 08 December 2015, D. Ertz 20869 (BR). KERGUELEN. Peninsule Courbet, Rivière du Sud, en amont de la cabane Jacky, 50 m, 49°19’21”S, 70°07’31”E, bloc rocheux au bord de la rivière, 13 January 2014, D. Ertz 18958 (BR); versant droit de la Rivière du Sud, Ravin du Mica, 150 m, 49°16’07.6”S, 70°03’11.1”E, 17 November 2016, D. Ertz 21011 (BR); Val Studer, 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 Novermber 2016, D. Ertz 20981, 20982, 20986 (BR); 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 Novermber 2016, D. Ertz 20994 (BR). Cirque du Chateau, on plateau around upper course of Rivière de la Grande Muraille c. 1–2 km S of la Grande Cascade , 250 m, 49°17’6”S, 70°07’9”E, 15 December 1998, R.S. Poulsen 171 (C); Mt. Crozier, just below and <150 m from summit, 950 m, 49°17’7”S, 69°59’1”E, 18 December 1998, R.S. Poulsen 295 (C); W end of Presqu’Île du Prince de Galles, Roche Verte, 110 m, 49°25’2”S, 70°19’6”E, 14 March 1999, R.S. Poulsen 1151 (C). Golfe du Morbihan, Île Australia, c. 3 m, 49°28’S, 69°52’E, 22 December 2013, D. Ertz 18761 (BR); Île Guillou, c. 14 m, 49°28’57”S, 69°49’06”E, 08 January 2014, D. Ertz 18862 (BR); Île Mayes, E end of the island 100–200 m from sea, 30 m, 49°28’2”S, 69°57’1”E, 17 December 1998, R.S. Poulsen 233 (60 m a.s.l.), 247, 261 (C). La Mortadelle, SE part (at the foot) of La Mortadelle, c. 0.5 km W of Lac Ampère, c. 100 m from cabin/shelter, 150 m, 49°25’4”S, 69°10’8”E, 17 January 1999, R.S. Poulsen 580a (C). Péninsule Rallier du Baty, Baie de la Mouche, N part of Les Restanques <300 m from coast, 25 m, 49°33’6”S, 69°03’5”E, 2 February 1999, R.S. Poulsen 748 (C); Les Deux Frères, at the SE foot of the mountain, 50 m, 49°38’4”S, 69°00’4”E, 5 February 1999, R.S. Poulsen 845 (C); E-most part of Arete Jérémine by W end of Anse du Gros Ventre, 20 m, 49°43’4”S, 68°55’5”E, 6 February 1999, R.S. Poulsen 880 (C).

Figures

FIGURE 4. Steinera isidiata. a–c Fertile and isidiate thalli (Ertz 20689). d Thallus almost entirely covered by isidia (Poulsen 233). e–f Sections of upper part of thallus (Ertz 20689). g Section of lower part of thallus (Ertz 20689). h Photobiont (Ertz 20689). i Ascus (Ertz 20689). j Ascospores in water (Ertz 20689). Scale bars: a=1.5 mm, b–d=0.5 mm, e=25 μm, f–i=10 μm, j=5 μm. (Photos D. Ertz)