Parmotrema mezierii D.M. Masson & Sérus., 2024

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 : 61-63

Parmotrema mezierii D.M. Masson & Sérus. , sp. nov. MycoBank no. 853871

Diagnosis. Similar to P. paulense (Zahlbr.) Hale but differs from it by the coralloid isidia and by the presence in the medulla of protolichesterinic and lichesterinic acids, in addition to norlobaridone and loxodin.

Holotype:— FRANCE. Réunion: Cilaos , eastern side of le Bonnet Carré, GR R1 trail, elev. 1350 m, 21°07’33”S, 55°28’13”E, in disturbed leeward montane rainforest, in an overall E orientation, on a shaded volcanic rock, 18 August 2015, D. Masson 974.4714 (MNHN-PC-PC0088074; isotype: LG).

GenBank accession numbers: ITS ( PP 840443), EF1-α ( PP 852831).

( Fig. 25 )

Thallus foliose, moderately adnate, membranaceous to subcoriaceous, up to 10 × 11 cm. Lobes irregular, sometimes contiguous but generally imbricate, irregularly branched, 3–11 mm wide, often concave, with margins sinuate to crenate, becoming dentate and sometimes revolute with the development of isidia, rarely lobulate, ciliate ( Fig. 25E ). Cilia black, rarely with coppery glints; moderately dense and ± evenly distributed at the lobe margins, also present on isidia, simple, very rarely once branched, ca. 0.03–0.05 mm in diameter at the base, up to 2.5 mm long. Upper surface greenish grey, pale or ± darkened, ± shiny, more so towards lobe tips, ± distinctly punctiform white-maculate, smooth to rugose, sometimes cracked in older parts, isidiate, lacking schizidia, pustules, dactyls, soralia; regeneration lobules occasionally present in older parts. Isidia marginal, extending submarginally and ± laminally; rapidly coralloid, sometimes irregularly flattened and then ± looking like phyllidia, very often apically and/or laterally ciliate; up to 3 mm high, brittle ( Fig. 25C & 25D ). Medulla white throughout. Lower surface rugulose, rarely smooth, exceptionally reticulate, shiny, duller in the central part, black to the margin, or with a buff or chestnut brown erhizinate marginal zone (ca. 2–6 mm wide) at main lobe tips, isidiate lateral lobes with an erhizinate, ivory white or ivory-mottled marginal zone (0.4–3 mm wide). Rhizines in ± scattered groups, concolor to the lower surface, young ones often with pale tips, simple, more rarely 1–2 times branched, up to 1.5 mm long. Apothecia absent. Pycnidia occasional, submarginal towards the lobe apices; only primordia seen. Conidia not found. Upper cortex palisade plectenchymatous, not fragile, (13)– 19.7 –(27) µm thick. Algal layer continuous, (13)– 19.5 –(25) µm thick. Medulla (72)– 83.2 –(98) µm thick. Lower cortex prosoplectenchymatous, (15)– 17.7– (20) µm thick.

Chemistry:— Spot tests and fluorescence: upper cortex K+ yellow, UV−; medulla K−, C−, KC + pinkish, P−, UV± white. Secondary metabolites ( TLC): upper cortex with atranorin and chloroatranorin; medulla with norlobaridone (major), protolichesterinic acid (major), lichesterinic acid (minor/trace), and loxodin (minor/trace); ± 1 undetermined ciliary pigment: PV.

Eponymy: The epithet commemorates Marie Eustache Mézières de Lépervanche (1808–1861), Justice of the Peace in Réunion, but also a naturalist interested in various aspects of the natural history of this island. He corresponded with several members of the French Academy of Sciences such as J.-B. Bory de Saint-Vincent, C.-F. Brisseau de Mirbel, C. Gaudichaud-Beaupré or A. Richard ( Maillard 1862). He collected many lichens ( Jacob de Cordemoy 1895), some of which were studied by Nylander (1859). In particular, a fine specimen of the new species was collected by him in 1840 and sent to Bory de Saint-Vincent. It was determined as Parmelia perlata var. ciliata by Nylander and is now kept at PC.

Geographical distribution:—So far only known from Réunion, where it seems to be rare. The earliest collection dates to 1840; since then, P. mezierii has been found at four localities in four UTM 1× 1 km grid cells (or three UTM 2× 2 km grid cells, Fig. 25A ). The documented localities are distributed over a fairly narrow range of elevations: 1005–1350 m, on the southern slopes of the Piton des Neiges massif, in the Cirque de Cilaos or nearby.

Ecology:— Parmotrema mezierii is a saxicolous and corticolous species; it was found twice thriving on volcanic rocks and twice on the bark of trunks of Ficus and Weinmannia . According to the scanty data available, three types of habitat are involved: submontane mesic forest, leeward submontane rainforest and leeward montane rainforest. The bioclimate of the four documented localities is pluvial tropical, thermotype belt = lower mesotropical (412 ≤ It ≤ 482), and ombrotype belt = upper humid (9.1 ≤ Io ≤ 10.4) ( Fig. 25B ).

Notes:—The phenotype of Parmotrema mezierii is close to that of P. paulense , a poorly known and apparently rare lichen, whose type was collected near São Paulo in Brazil ( Zahlbruckner 1909). The circumscription of this last taxon is still rather unclear, mainly due to the paucity of available material. Hale’s concept of the species, in his world monograph of Parmelia subgenus Amphigymnia ( Hale 1965a) , was broad since it included specimens belonging to two other taxa from Africa, Parmotrema dolosum (Abbayes) Hale and P. diacidulum (Hale) Hale [both synonymized with P. lophogenum (Abbayes) Hale by Krog & Swinscow (1975)], and a specimen from Réunion, identified in the present work as P. intonsum (see ‘Erroneous, doubtful and problematic reports’). Later on, Kurokawa (1969) stated that the medulla of the type of P. paulense contains norlobaridone and loxodine, while Hale (1971b) pointed out that both P. dolosum and P. diacidulum have a different chemistry, with gyrophoric acid and a fatty acid in the medulla. The two authors concluded that P. paulense was represented only by the type collection from Brazil. Recently, however, P. paulense was reported from Mexico ( Ryan et al. 2000, Egan et al. 2016). Unfortunately, the morphological and anatomical descriptions of this species in Egan et al. (2016) are based on Hale (1965a), and hence on an inaccurate concept of the species. As for the medullary substances, they are listed by Egan et al. (2016) as norlobaridone and ‘protolichesteric’ acid. Therefore, it is difficult for us to draw conclusions about the taxonomic status of the Mexican material. Our own study of the type collection of P. paulense gives results that are consistent with the comments of Kurokawa (1969). In the protologue, Zahlbruckner (1909) stated that the species lacked vegetative propagules, but close examination of thalli shows the presence of small (not more than 0.7 mm high), granular or ± cylindrical, often ciliate, isidia. Thin layer chromatography revealed the existence of norlobaridone (and loxodin?) in the medulla as well as the absence of any fatty acid (at least in detectable amounts). The ciliary pigment PV was also detected. Without knowing the intraspecific variability of P. paulense and without molecular data [examination of the Colombian specimen cited in Stelate et al. (2022) reveals that it actually belongs to P. mellissii , which is consistent with its position in the phylogenetic tree based on ITS sequences], it is difficult to assess whether the Reunionese material belongs to this Neotropical species or not. The wide disjunction from Réunion to Brazil, the constant occurrence of protolichesterinic acid as a major medullary substance, and the regular presence of well-developed coralloid isidia lead us nevertheless to propose a distinct status for the taxon present on Réunion.

Phylogenetic analysis of a 3-locus data matrix revealed that P. mezierii belongs to a strongly supported radiation, comprising ten Reunionese species ( Fig. 3 ). Five of them, including P. mezierii , are possibly endemic to Réunion or the Mascarenes.

Additional specimens examined (paratypes):— FRANCE. Réunion: without locality, 1840, M.E. Mézières de Lépervanche 25 ( PC 0009292 ) ; Cilaos, Ravine des Calumets , NE of Palmiste Rouge, elev. 1075 m, 21°09’42”S, 55°29’23”E, in the bottom of a ravine, in an overall SW orientation, on a 50° sloping face, a little shaded and facing N, of a basaltic rock, in a disturbed submontane mesic forest, 21 August 2012, D. Masson 974.3960 ( LG) ; Saint-Louis, Les Makes, Bois Bon Accueil , elev. 1170 m, 21°11’35”S, 55°23’50”E, in leeward montane rainforest, in an overall S orientation, on the bark of a trunk of Weinmannia sp. , 28 August 2017, D. Masson 974.5159 ( LG) ; ibid., elev. 1005 m, 21°11’57”S, 55°23’58”E, in leeward submontane rainforest, in an overall S orientation, on the bark of a trunk of an old Ficus densifolia , 28 August 2017, D. Masson 974.5226 (Hb. DM) .

Specimens studied for comparison:

Parmotrema paulense .— BRAZIL. São Paulo: In monte Jaraguá prope Taipas , elev. 800–1050 m, corticola, June 1901, V. Schiffner s.n. (W, type collection) .

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 25. Parmotrema mezierii. 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 & D: Isidiate lobes with isidia rapidly coralloid, and ± apically and/or laterally ciliate (C: Masson 974.3960, D: holotype); E: Gross morphology of thallus (holotype). Scale bars:A = 10 km; C, D = 4 mm; E = 10 mm.