Parmotrema mascarenense D. M. Masson & Serus., sp. nov.
Creators: name: Masson, Didier
name: Magain, Nicolas
name: Sérusiaux, Emmanuël
Publisher: name: Zenodo
Year: 2024
Subjects: Biodiversity
Taxonomy
Fungi
Ascomycota
Lecanoromycetes
Lecanorales
Parmeliaceae
Parmotrema
Parmotrema mascarenense

description: Parmotrema mascarenense D.M. Masson & Sérus., sp. nov. MycoBank no. 853870
Diagnosis. Superficially similar to P. sanctae-candidae Eliasaro and sharing the same chemistry, but differs mainly by the effigurate, and not truly reticulate, maculation of the upper surface, the more branched isidia that do not become sorediate, and by the clustered rhizinae not extending to the margin of lobe tips.
Holotype:— FRANCE. Réunion: La Possession, la Grande Montagne, sentier des Lataniers, elev. 1330 m, 20°58’17”S, 55°23’30”E, in leeward montane rainforest, in an overall NW orientation, on bark of a branch of Erica reunionensis, 19 August 2015, D. Masson 974.4732 (MNHN-PC-PC0088073).
GenBank accession numbers: ITS (PP 840449), mtSSU (PP 842574), EF1-α (PP 852835).
(Fig. 22)
Thallus foliose, moderately adnate, membranaceous to coriaceous, up to 11 × 17 cm. Lobes imbricate, irregular, ± rounded towards apices, 2–13 mm wide, isidiate lateral lobes frequently revolute and forming cone-shaped, or Tshaped, raised structures; margins sinuate to crenate, becoming ± dentate with the development of isidia, rarely shortly laciniate or lobulate, irregularly ciliate or eciliate (Fig. 22E). Cilia black, with density very variable among thalli, mostly unevenly distributed at the lobe margins, often ± in clumps in lobe axils (Fig. 22D), sometimes present on isidia, simple to 4 times branched, occasionally ± squarrose, ca. 0.03–0.10 mm in diameter at the base, up to 4 mm long. Upper surface pale greenish grey, rather dull, somewhat shinier towards lobe tips, rugose, generally distinctly effigurate white-maculate, old parts often finely cracked, sometimes with a subreticular pattern; isidiate, lacking schizidia, pustules, dactyls, soralia. Isidia marginal, extending submarginally and laminally; simple and cylindrical to coralloid (Fig. 22C), at times granular, seldom slightly flattened, occasionally apically and/or laterally ciliate, up to 3.5 mm high. Laciniae rare, marginal, up to 1 × 2 mm. Lobules occasional, marginal, up to 6 × 7 mm. Medulla white throughout; exceptionally, and very locally, coloured orange-yellow by a K- pigment. Lower surface smooth or rugulose, granulose in places, quite often cracked, shiny, duller in the central part, black to the margin, or with a chestnut brown, or tan, erhizinate marginal zone (ca. 1–10 mm wide) at main lobe tips, isidiate lateral lobes often with an erhizinate, ivory white or ivory-mottled marginal zone (0.5–4 mm wide), some revolute isidiate lobes may even have a completely ivory white underside. Rhizines in ± scattered groups, concolor to the lower surface, simple, very rarely furcate, generally quite short but some can reach 3 mm long. Apothecia very rare; one thallus (no 974.4312) with a few minute submarginal apothecia, up to 0.8 mm in diameter, amphithecium isidiate. Ascospores absent. Pycnidia quite frequent, mainly on isidia but also marginal towards lobe apices, black. Conidia bacilliform, straight or slightly curved, 5–6 × ca. 1 µm. Upper cortex palisade plectenchymatous, not fragile, (14)– 18.7 –(30) µm thick. Algal layer here and there briefly interrupted, (10)– 18.9 –(24) µm thick. Medulla (75)– 100.9 –(115) µm thick. Lower cortex prosoplectenchymatous, (17)– 19.2– (20) µm thick.
Chemistry:— Spot tests and fluorescence: upper cortex K+ yellow, UV−; medulla K+ slowly orange brown, C−, KC−, P+ orange, UV−. Secondary metabolites (TLC): upper cortex with atranorin and chloroatranorin; medulla with succinprotocetraric acid (major), fumarprotocetraric acid (minor/trace), ± virensic acid (trace), ± unidentified substance (grey; Rf classes:A3, B5, C 5; trace).
Etymology: The species name is based on its occurrence on Réunion and Mauritius, two islands of the Mascarene Archipelago.
Geographical distribution:—This lichen is so far only known from the two largest islands of the Mascarenes. It seems to be relatively frequent on Réunion, having been collected at 25 localities in 24 UTM 1× 1 km grid cells (or 21 UTM 2× 2 km grid cells, Fig. 22A). These localities are distributed at elevations between 570 and 1500 m, mainly in the Piton des Neiges massif but also on the southwestern slopes of the Piton de la Fournaise massif. In Mauritius, P. mascarenense is known from 6 localities, between 565 and 700 m elevation, in the southwestern part of the island.
Ecology:—On Réunion, Parmotrema mascarenense is mainly corticolous, but it was also found on basaltic rocks in one location. The trees and shrubs that are phorophytes are indigenous and belong to various genera: Antidesma, Aphloia, Dombeya, Erica, Ficus, Gaertnera, Melicope, Molinea, Ocotea, Pandanus, Pittosporum, and Weinmannia. This Parmotrema was found significantly more often on trunks (21 occurrences) than on branches (seven occurrences) (χ² test with Yates correction, P = 0.0070, one-tailed). Leeward montane rainforest is the main habitat the species occurs in (43% of the localities), but P. mascarenense was also collected in windward submontane rainforest (22%), windward montane rainforest (13%), leeward submontane rainforest (13%), submontane mesic forest (4%) or lowland dry forest (4%). The bioclimates of the localities are pluviseasonal tropical and pluvial tropical; thermotype belts are mainly mesotropical = from upper thermotropical to upper mesotropical (355 ≤ It ≤ 585), ombrotype belts are very variable = from upper subhumid to ultrahyperhumid (5.7 ≤ Io ≤ 29.3) (Fig. 22B). In Mauritius, the species was found on tree bark, in localities with bioclimatic features (thermotype belt = upper thermotropical, ombrotype belt = lower humid) similar to those of some Reunionese stations.
Notes:—All thalli of Parmotrema mascarenense whose medullary chemistry was investigated by TLC have succinprotocetraric acid as main substance, as well as fumarprotocetraric acid always in lesser amounts. There is no evidence of the presence of the related compound protocetraric acid. Only four isidiate species of the genus Parmotrema containing succinprotocetraric acid are currently known: P. acrotrychum (Kurok.) Streimann, P. adspersum (Vain.) Elix, P. sanctae-candidae, and P. tongaense Elix. Parmotrema acrotrychum and P. tongaense differ from P. mascarenense mainly by the emaculate upper surface and by the additional presence of the protolichesterinic acid in the medulla (Kurokawa 1979, Elix 1996). Furthermore, our molecular investigations suggest that P. acrotrychum is a chemical variant of P. subcorallinum, phylogenetically distant from P. mascarenense (see the entry for P. subcorallinum, and Fig. 3). Unlike P. mascarenense, P. adspersum has an emaculate upper surface and its lobe margins and isidia are eciliate (Vainio 1907, Hale 1976). With its strong reticulate maculation on the upper surface and rhizines that often extend to the lobe margins, the Brazilian P. sanctae-candidae is similar to species previously included in the genus Rimelia Hale & A. Fletcher (Eliasaro 2008), and differs from P. mascarenense precisely in these features. To our knowledge, there does not seem to be a morphological equivalent to P. mascarenense with protocetraric acid as a major medullary extrolite.
Specimens from Mauritius are phenotypically similar to those from Réunion. At most, they tend to have slightly narrower lobes (2–7 mm) with more lobulate and laciniate margins, and less frequently coralloid isidia. A few Reunionese thalli from low elevation localities show this kind of morphology. Both Mauritian and Reunionese samples were resolved in the same well-supported clade in our phylogenetic trees (Fig. 3 & 4) and, as demonstrated by phylogenetic analyses, P. mascarenense belongs to a well-supported clade comprising two other species, either described as new in this paper (P. aurantioreagens) or already described (P. meiospermum). All three could be endemic to the Mascarene Islands (Table 1).
Additional specimens examined (paratypes):— FRANCE. Réunion:Bras-Panon, sentier de la Caroline, elev. 760 m, 21°01’42”S, 55°37’08”E, in disturbed windward submontane rainforest, on bark of trunks of Gaertnera vaginata and of an undetermined tree, 15 August 2017, D. Masson 974.4954 (Hb. DM), 974.4955 (LG); Cilaos, Ravine des Calumets, NE of Palmiste Rouge, elev. 1140 m, 21°09’34”S, 55°29’26”E, in the bottom of a ravine, in an overall south orientation, on 75 and 90° sloping faces, hardly shaded and facing NE and E, of basaltic rocks, in a disturbed submontane mesic forest, 21 August 2012, D. Masson 974.3951 (REU), 974.3954 (Hb. DM); ibid., Plateau des Chênes, elev. 1350 m, 21°07’36”S, 55°28’19”E, in leeward montane rainforest, in an overall south orientation, on bark of a trunk of Antidesma madagascariense, 18 August 2015, D. Masson 974.4710 (LG); ibid., Cirque de Cilaos, along trail (GR R2) in canyon just W of Cilaos town, elev. 1150 m, 21°07’48”S, 55°28’12”E, 02 October 1996, H. Krog RE34/3, RE34/4 & E. Timdal (O); Entre-Deux, sentier de la Grande Jument, elev. 1130 m, 21°12’45”S, 55°28’59”E, in leeward montane rainforest, in an overall south orientation, on bark of a trunk of Pittosporum senacia, 16 August 2015, D. Masson 974.4667 (Hb. DM); La Possession, Dos d’Âne, Piton Grand Bazar, elev. 1330 m, 20°58’25”S, 55°23’25”E, in leeward montane rainforest, in an overall NW orientation, on bark of a trunk of Dombeya sp., 19 August 2015, D. Masson 974.4722 (Hb. DM); ibid., la Grande Montagne, sentier des Lataniers, elev. 1330 m, 20°58’17”S, 55°23’30”E, in leeward montane rainforest, in an overall NW orientation, on bark of a branch of Erica reunionensis, 19 August 2015, D. Masson 974.4732 (Hb. DM); ibid., elev. 1330 m, 20°58’11”S, 55°23’37”E, in leeward montane rainforest, in an overall NW orientation, on bark of a trunk of Dombeya sp., 19 August 2015, D. Masson 974.4733 (Hb. DM); ibid., Cirque de Mafate, Sentier Scout, elev. 1480 m, 21°03’10”S, 55°26’49”E, in leeward montane rainforest, on bark of a trunk of Dombeya sp., 24 July 2005, D. Masson 974.1714 (Hb. DM); L’Étang-Salé, Chemin Canal, elev. 1030 m, 21°12’50”S, 55°22’32”E, in leeward submontane rainforest, on bark of Erica reunionensis, 27 August 2017, D. Masson 974.5139 (LG); Saint-André, forêt de Dioré, elev. 825 m, 20°59’36”S, 55°34’55”E, in windward submontane rainforest, on bark of branches of Pandanus montanus, 21 August 2017, D. Masson 974.5057 (LG), 974.5228 (Hb. DM); Saint-Benoît, Piton de Bébour, elev. 1390 m, 21°07’33”S, 55°33’52”E, in windward montane rainforest, on bark of a trunk of Dombeya sp., 07 April 2003, D. Masson 974.1210 (Hb. DM); ibid., Takamaka, elev. 740 m, 21°05’27”S, 55°37’04”E, in windward submontane rainforest, in an overall south orientation, on bark of trunk of an undetermined tree, 24 August 2013, D. Masson 974.4430 (LG); Saint-Denis, Plaine d’Affouches, elev. 1460 m, 20°59’00”S, 55°24’22”E, in leeward montane rainforest, on bark of trunks of Aphloia theiformis and Gaertnera vaginata, 04 August 2005, D. Masson 974.1943 (REU), 974.1954 (Hb. DM); ibid., elev. 1485 m, 20°58’58”S, 55°24’50”E, in leeward montane rainforest, on bark of a branch of Erica reunionensis, 18 August 2012, D. Masson 974.3865 (LG); Saint-Joseph, Grand Coude, elev. 1415 m, 21°16’24”S, 55°37’52”E, in windward montane rainforest, on bark of trunk of an undetermined young tree, 24 August 2017, D. Masson 974.5115 (Hb. DM); ibid., sentier du Piton du Rond, elev. 1140–1175 m, 21°18’29–32”S, 55°36’04–06”E, in leeward submontane rainforest, in overall S–SW orientation, on bark of a branch of a big Ficus sp. and a trunk of Weinmannia sp., 18 August 2013, D. Masson 974.4295 (REU), 974.4296, 974.4298 (Hb. DM); ibid., elev. 1260 m, 21°18’15”S, 55°36’11”E, in leeward submontane rainforest, in an overall SSW orientation, on bark of trunk of Dombeya sp., 18 August 2013, D. Masson 974.4313 (Hb. DM); ibid., Piton du Rond, elev. 1375 m, 21°17’55”S, 55°36’23”E, in leeward submontane rainforest, on bark of trunk of Molinea alternifolia, 18 August 2013, D. Masson 974.4312 (Hb. DM); Saint-Louis, Les Makes, Bois Bon Accueil, elev. 1005 m, 21°11’57”S, 55°23’58”E, in leeward submontane rainforest, in an overall south orientation, on bark at the base of a trunk of an old Ficus densifolia, 28 August 2017, D. Masson 974.5144 (Hb. DM); ibid., elev. 1145 m, 21°11’38”S, 55°24’06”E, in leeward submontane rainforest, on bark of trunk of an undetermined tree, 28 August 2017, D. Masson 974.5148 (LG); Saint-Philippe, forêt de Saint-Philippe, sentier de Piton Ravine Basse Vallée, elev. 910 m, 21°19’53”S, 55°42’16”E, in windward submontane rainforest, in an overall SSW orientation, on ± mossy bark of a trunk of a young Ocotea obtusata, 16 August 2013, D. Masson 974.4254 (Hb. DM); Saint-Pierre, Piton de Mont Vert, elev. 570–590 m, 21°19’37–38”S, 55°32’28–32”E, in lowland dry forest, on bark of trunks of undetermined trees, 19 August 2017, D. Masson 974.5009, 974.5010 (Hb. DM), 974.5017 (LG); Salazie, Piton d’Enchain, elev. 1350 m, 21°02’37”S, 55°29’53–55”E, in windward montane rainforest, on bark of Melicope borbonica and on bark of trunks of undetermined trees, 13 April 2003, D. Masson 974.0301 (REU), 974.0305, 974.0320, 974.0324 (Hb. DM); ibid., Forêt de Bélouve, track from Gîte de Bélouve to viewpoint, elev. 1500 m, 21°03’39”S, 55°32’10”E, 30 September 1996, H. Krog RE25/27 & E. Timdal (O).
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 19181, 19192 & D. Ertz (Hb. P. Diederich); ibid., Trou aux Cerfs, along road surrounding the crater, elev. 580–605 m, 20.31794°S, 57.51147°E, on the bark of a tree, 30 July 2016, P. Diederich 18281 (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 bark of trees, 01 August 2016, P. Diederich 18331, 18596 (Hb P. Diederich); ibid., along the trail west of Pétrin Information Centre, up to 600 m W of first viewpoint, elev. 620–660 m, 20.40038°S, 57.45669°E, on the bark of a tree, 31 August 2019, P. Diederich 18757 & D. Ertz (Hb P. Diederich); Rivière Noire District: Black River Gorges National Park, 5 Km NW of Pétrin, Brise Fer Forest, elev. 585 m, 20.37787°S, 57.44035°E, on bark of trees, 10 September 2019, P. Diederich 19222, 19410, 19424 & D. Ertz (Hb. P. Diederich); ibid., along trail to Piton de la Petite Rivière Noire, elev. 630–700 m, 20.42133°S, 57.41947°E, on the bark of a tree, 05 August 2016, P. Diederich 18413 (Hb. P. Diederich).
Specimen studied for comparison:
Parmotrema sanctae-candidae.— BRAZIL. Paraná: General Carneiro, Fazenda Santa Cândida, 30 October 2004, S. Eliasaro 2794 (UPCB, paratype).
description: Published as part of 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, pp. 1-138 in Phytotaxa 657 (1) on pages 54-57, DOI: 10.11646/phytotaxa.657.1.1, http://zenodo.org/record/13217474