Parmotrema subcorallinum (Hale) Hale (1974a: 339) MycoBank

Masson, Didier, Magain, Nicolas & Sérusiaux, Emmanuël, 2024, Small island but great diversity: thirty six species of Parmotrema (Parmeliaceae, lichenized Ascomycota), including sixteen new species, on Réunion (Mascarenes), with additional data from the Western Indian Ocean, Phytotaxa 657 (1), pp. 1-138 : 102-104

Parmotrema subcorallinum (Hale) Hale (1974a: 339) MycoBank no. 343133

Parmelia subcorallina Hale (1962: 345) MycoBank no. 345524

Type:— TAIWAN. Taichung: Keitau , 24 December 1933, Y. Asahina 3312 ( TNS!, holotype; US [image!], isotype) .

Parmelia acrotrycha Kurok. (1979: 126) , syn. nov. MycoBank no. 115850

Type:— PAPUA NEW GUINEA. Eastern Highland District : Kundibesa logging area, 22 miles east of Kainantu, 1560 m, 18 November 1965, S. Kurokawa 6086 ( TNS, n.v., holotype) .

= Parmotrema acrotrychum (Kurok.) Streimann (1986: 92) MycoBank no. 129345

( Fig. 38 )

Description and chemistry are based on specimens from Réunion ( P. subcorallinum s. str.).

Thallus foliose, loosely to moderately adnate, membranaceous, up to 13 × 16 cm. Lobes rounded, imbricate, irregularly branched, 4–12 mm wide, often concave; margins ascending, crenate to isidiate-dissected, ciliate ( Fig. 38C ). Cilia conspicuous, black, sometimes with coppery glints (pigments), abundant, simple, up to 5 mm long. Upper surface pale greenish grey, emaculate or faintly white-maculate, ± cracked and somewhat scrobiculate in the older parts, isidiate, lacking schizidia, pustules, dactyls, phyllidia and soralia; regeneration lobules occasionally present in older parts. Isidia mainly marginal and submarginal, occasionally also laminal in older parts, very often apically ciliate, irregular, at first granular or cylindrical, then ± coralloid or arbuscular and inflated, up to 2 mm high, brittle ( Fig. 38D ). Medulla white throughout. Lower surface ± shiny, smooth to rugulose, black to the margin, or with a chestnut brown or buff erhizinate marginal zone (ca. 1–8 mm wide) at main lobe tips, isidiate lateral lobes often with a narrow (0.2–1.2 mm), erhizinate, ivory white marginal zone. Rhizines concolor to the lower surface, in scattered groups, simple, sometimes furcate or 1–2 branched, up to 2.5 mm long. Apothecia not seen in the specimens examined. Pycnidia rare, submarginal towards apices; only primordia seen. Conidia not found.

Chemistry:— Spot tests and fluorescence: upper cortex K+ yellow, UV−; medulla K−, C−, KC+ fleeting pinkish, P+ orange, UV−. Secondary metabolites (TLC): upper cortex with atranorin and chloroatranorin; medulla with protocetraric acid (major), protolichesterinic acid (major), lichesterinic acid (minor or trace), ± undetermined fatty acid (Rf classes:A2-3, B1, C2; minor); ± 2 undetermined ciliary pigments: P1, PV.

Geographical distribution:— Parmotrema subcorallinum is a paleotropical species with a curious insular/ peninsular distribution. Specimens with protocetraric acid ( P. subcorallinum s. str.) have been reported from Taiwan ( Hale 1962, Kurukowa & Lai 2001), Hainan Island ( Chen et al. 2005), Java ( Hale 1965a), the Malay Peninsula ( GBIF 2022b), Borneo ( Din et al. 1999), New Guinea ( Louwhoff & Elix 1999), Seychelles ( Seaward & Aptroot 2009, Diederich et al. 2017), Mauritius ( Hale 1962, Diederich & Ertz 2020, present work), and São Tomé Island ( Hale 1965a). They are here reported as new for Réunion from nine localities in eight UTM 1× 1 km grid cells (or seven UTM 2× 2 km grid cells, Fig. 38A ). These localities are located on the windward part of the island, between 685 and 1395 m elevation. Specimens with succinprotocetraric and fumarprotocetraric acids ( P. acrotrychum ) have been reported from Borneo ( Din et al. 1999, 2008), New Guinea and northern Queensland in Australia ( Kurokawa 1979, Elix 1994, Louwhoff & Elix 1999). They have also been collected at two locations in Mauritius, between 565 and 680 m elevation (Diederich & Ertz 2020; also herein).

Ecology:—On Réunion, Parmotrema subcorallinum was found in two types of habitats, Pandanus submontane wet thicket and windward submontane rainforest, where it was corticolous on branches and trunks of trees (especially Pandanus montanus ). Its localization on the windward side of the island and at medium elevation (685–1395 m) suggests that it is an ombrophilous and moderately thermophilous species. Bioclimatic features of the localities ( Fig. 38B ) can be summarized as follow: bioclimate pluvial tropical, thermotype belts = upper thermotropical and lower mesotropical (425 ≤ It ≤ 542), ombrotype belts = from lower hyperhumid to ultrahyperhumid (12.7 ≤ Io ≤ 27.1). In Mauritius, the species was collected between 565 and 750 m elevation; on Mahé Island ( Seychelles), between 600 and 800 m ( Seaward & Aptroot 2009, Diederich et al. 2017).

Notes:—All the collections from Réunion and one from Mauritius examined by TLC contain protocetraric, protolichesterinic and lichesterinic acids as constant medullary extrolites. Two specimens from Mauritius contain succinprotocetraric, fumarprotocetraric, protolichesterinic and lichesterinic acids in their medullae, which react K+ slowly brick red, C-, KC-, P+ orange. They are morphologically indistinguishable from those containing protocetraric acid. They also contain the same two ciliary pigments: P1 and PV. These two Mauritian specimens fit morphologically and chemically with Parmotrema acrotrychum described from Papua New Guinea and Australia ( Kurokawa 1979). According to Kurokawa (1979), Elix (1994) and Louwhoff & Elix (1999), P. acrotrychum and P. subcorallinum are closely related and differ mainly in medullary chemistry. A subtle distinction in the shape of the isidia was proposed by Kurokawa (1979): ‘isidia of P. subcorallina often become granular (…), those of P. acrotrycha are usually coralloid in shape’. However, we were unable to find any correlation between isidia morphology and medullary chemistry in the Mascarene material examined.

Our phylogenetic study based on three loci from five specimens from Réunion with protocetraric acid and two specimens from Mauritius with succinprotocetraric and fumarprotocetraric acids further show that a single taxon is involved and can be recovered with phylogenetic inferences ( Fig. 3 ). We therefore propose to place P. acrotrychum in synonymy with P. subcorallinum , and distinguish two chemotypes within P. subcorallinum , one with protocetraric acid as major substance, the other with the biosynthetically related succinprotocetraric and fumarprotocetraric acids.

Parmotrema subcorallinum can be confused with P. kaisenikianum (Kurok.) Streimann , which appears to be endemic to Papua New Guinea, but the latter species has eciliate isidia and its medulla lacks protolichesterinic acid ( Kurokawa 1985, Louwhoff & Elix 1999).

In our 3-locus phylogenetic tree, the isidiate P. subcorallinum formed part of a well-supported clade that also included the sorediate P. eleonomum ( Fig. 3 ). Both species further belong to a strongly supported radiation, comprising a total of ten species, either described as new in this paper (eight) or already described (two).

Specimens with protocetraric acid examined:— FRANCE. Réunion: Bras-Panon, sentier de la Caroline, elev. 710 m, 21°01’36”S, 55°37’11”E, in windward submontane secondary rainforest with small Pandanus wet thickets, on bark of a trunk of Pandanus montanus , 15 August 2017, D. Masson 974.4961 (LG); ibid., La Plaine des Lianes, elev. 750 m, 21°01’52”S, 55°36’39”E, on bark, 01 October 1996, H. Krog RE32/9, RE32/10, RE32/11 & E. Timdal (O L-231245, L-231246, L-231247); La Plaine-des-Palmistes, Ligne Deux Mille en Dessous, elev. 870 m, 21°07’03”S, 55°39’05”E, in Pandanus submontane wet thicket, on bark of a branch of Agauria sp. , 18 August 2017, D. Masson 974.5001 (LG), 974.5002 (Hb. DM); Saint-André, forêt de Dioré, elev. 825 m, 20°59’36”S, 55°34’55”E, in windward submontane secondary rainforest, on bark of a branch of Pandanus montanus , 21 August 2017, D. Masson 974.5058 (LG); Saint-Benoît, Saint-François les Hauts, sentier Sainte-Marguerite, elev. 685 m, 21°06’57”S, 55°40’42”E, in Pandanus submontane wet thicket, on bark of Pandanus montanus , 28 August 2012 and 23 August 2015, D. Masson 974.4108 (Hb. DM), 974.4836 (LG); ibid., elev. 725 m, 21°07’11”S, 55°40’39”E, in Pandanus submontane wet thicket, on bark of a branch of Pandanus montanus , 28 August 2012, D. Masson 974.4116 (Hb. DM); Saint-Joseph, Grand Coude, elev. 1395 m, 21°16’28”S, 55°37’51”E, in windward montane rainforest, on bark of a branch of Pandanus montanus , 24 August 2017, D. Masson 974.5116 (LG); Sainte-Suzanne, les Hauts de la Perrière, elev. 765 m, 20°58’48”S, 55°34’06”E, open picnic place in a windward submontane secondary rainforest, on bark of a trunk of an undetermined tree, 11 August 2015, D. Masson 974.4590 (LG); ibid., ravine Bras Laurent, elev. 755 m, 20°58’49”S, 55°33’48”E, edge of a ravine in a windward submontane secondary rainforest, on bark of a branch of an undetermined tree, 11 August 2015, D. Masson 974.4591 (Hb. DM).

MAURITIUS. Savanne District: Black River Gorges National Park, along the trail to Mt Cocotte , elev. 720–750 m, 20.44174°S, 57.47106°E, on the bark of a tree, 01 September 2019, P. Diederich 18884 & D. Ertz (Hb. P. Diederich) .

Specimens with succinprotocetraric and fumarprotocetraric acids examined:— MAURITIUS. Plaines Wilhems District: Curepipe, Curepipe Botanic Gardens , elev. 565 m, 20.32505°S, 57.51389°E, on bark of trees, 09 September 2019, P. Diederich 19114 & D. Ertz (Hb. P. Diederich); ibid ., Black River Gorges National Park, Le Pétrin, between Pétrin Information Centre and the first viewpoint along the trail to the west, elev. 610–680 m, 20.40189°S, 57.45883°E, on the bark of a tree, 01 August 2016, P. Diederich 18332 (Hb P. Diederich) .

Figures

FIGURE 3. Phylogeny of the Parmotrema species studied. Best ML tree resulted from a RaxML analysis of three loci (EF1-α, ITS, mtSSU) and 102 specimens. Punctelia toxodes was selected as the outgroup. Bootstrap values are represented above the branches, and thick branches have bootstrap support value ≥ 70. Results of the species delimitation analyses are summarized to the right of the terminal labels of the tree. The first column corresponds to the results of the Stacey analysis, while the second column corresponds to the results of the bPP analysis. Specimens attributed the same colour were reconstructed as part of the same putative species by the species delimitation analysis. Major medullary extrolites are also shown for each specimen.

FIGURE 38. Parmotrema subcorallinum. A: Distribution on Réunion (UTM 2×2 km grid system); B: Bioclimatic characteristics of collection sites (abbreviations and threshold values for thermotype and ombrotype horizons from Rivas-Martínez et al. 2011: 17–18); C: Gross morphology of thallus (Masson 974.4961); D: Lobes with irregular isidia, at first granular or cylindrical, then ± coralloid or arbuscular and inflated, often apically ciliate (Masson 974.4961). Scale bars: A = 10 km; C = 10 mm; D = 4 mm