Parmotrema mirum 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 : 63-68

Parmotrema mirum D.M. Masson & Sérus. , sp. nov. MycoBank no. 853872

Diagnosis. Ascospores, conidia and chemistry similar to Parmotrema subrugatum (Kremp.) Hale , but differs mainly by the constant presence of abundant and well-developed isidioid protuberances on the surface of the thalline exciple, by the constricted stipe of the apothecium, and by the lower cortex without a white or cream marginal zone.

Holotype:— FRANCE. Réunion: Le Tampon, Piton Textor trail, elev. 1865 m, 21°10’44”S, 55°38’11”E, in windward montane rainforest, in an overall north orientation, on the bark of small branches of Tambourissa sp. , 27 August 2012, D. Masson 974.4089 (MNHN-PC-PC0088075; isotype: LG).

GenBank accession numbers: ITS ( PP 840541), mtSSU ( PP 842527).

( Fig. 26 )

Thallus foliose, moderately adnate, membranaceous to coriaceous, up to 12 cm long, 5 cm wide. Lobes often ± elongated along the axis of the support (branch), irregularly or ± dichotomously branched, contiguous to imbricate, 3–12 mm wide, irregularly wrinkled, apices rounded; with margins sinuate, denticulate to laciniate, rarely lobulate, ± ciliate ( Fig. 26E ). Cilia rare to numerous, black, mostly irregularly distributed at the lobe margins, also occasionally present at the margin of laciniae, on isidioid protuberances of the amphithecium ( Fig. 26C ), and at the tip of isidia, simple, rarely forked, ca. 0.03–0.09 mm in diameter at the base, up to 2.5 mm long. Upper surface pale greenish grey, ± shiny, without maculae (except at the base of some apothecia), smooth to rugose, not cracked, isidiate or not, lacking schizidia, pustules, dactyls, soralia. Isidia present in 16 of the 26 thalli examined ( Fig. 26D ), laminal, sometimes also marginal, irregularly distributed, quite often in clusters, cylindrical to navicular, terete to ± flattened, mostly simple, rarely 1–2 times branched, occasionally apically ciliate, up to 0.7 mm high, up to 0.25 mm thick, sometimes develop into phyllidia. Laciniae marginal, usually numerous, elongated, fairly short (<1 mm long) and narrow (0.2–0.3 mm wide), not or hardly branched, at times ± canaliculate with subterete apex, sometimes ciliate, occasionally much more developed (up to 5 mm long and 1 mm wide) and repeatedly branched. Lobules occasional, marginal, up to 5 × 5 mm. Medulla white throughout. Lower surface rugulose, fairly shiny, especially on the periphery; black to the margin, or with a chestnut brown or grey-brown marginal zone (ca. 2–6 mm wide), especially at main lobe tips; often becoming ivory or cream under apothecia. Rhizines rather numerous, unevenly distributed, sometimes extending to the margin of the lobes, concolor to the lower surface, simple, rarely 1–(2) times branched, up to 1.5 mm long. Apothecia common, laminal and submarginal, up to 10 mm in diameter, shortly stipitate on constricted stipes (up to 1.8 mm in diameter); disc perforate or imperforate, irrespective of the stage of development of the apothecium (diameter of the smallest apothecium with perforate disc = 1.3 mm), orange brown to reddish brown, ± shiny, first concave, then ± flattening with age; thalline margin, amphithecium, and later on sometimes also stipe, early developing numerous, coarse, irregular, ± flattened, and ± branched isidioid protuberances (up to 3 mm long) which occasionally bear cilia and pycnidia ( Fig. 26C ); hymenium s. lat. (150)– 158.2 –(175) µm high, proper exciple with hyaline layer (6)– 11.1 –(15) µm high, intermediate layer (7)– 11.4 –(13) µm high, cortex-like basal layer (10)– 14.6 –(20) µm high. Ascospores 8 per ascus, simple, colourless, ellipsoidal, (26)29– 33.8 –38.5(43) × (13)14.5– 17.6 –20.5(21.5) µm, Q = (1.44)1.59– 1.94 – 2.29(2.50), epispore (2)– 3.6 –(4.5) µm thick, n = 330, from 11 thalli, mean values for each thallus: 31.6 × 16.8, 32.4 × 16.4, 32.4 × 18.3, 32.5 × 17.6, 33.2 × 16.8, 33.3 × 16.7, 34.7 × 19.2, 35.1 × 18.5, 35.4 × 17.9, 35.5 × 17.6, 35.8 × 17.4 µm. Pycnidia frequent, mostly submarginal, sometimes also on laciniae or lobules, black. Conidia unciform to bacilliform 4.5–5.5 × ca. 1 µm. Upper cortex palisade plectenchymatous, not fragile, (17)– 19.1 –(23) µm thick. Algal layer continuous, (12)– 17.2 –(20) µm thick. Medulla (95)– 100.5 –(107) µm thick. Lower cortex prosoplectenchymatous, (12)– 14.0– (15) µm thick.

Chemistry:— Spot tests and fluorescence: upper cortex K+ yellow, UV−; medulla K−, C−, KC + fleeting purple pink, then orange, P−, UV+ blue-white. Secondary metabolites ( TLC): upper cortex with atranorin and chloroatranorin; medulla with alectoronic acid (major, constant), ± α-collatolic acid (major, present in 46% of the investigated thalli), ± 1–2 undetermined substances, most probably of the alectoronic acid chemosyndrome (minor/trace).

Etymology: From the Latin mirus: surprising, remarkable. The specific epithet relates to the unusual outgrowths on thalline exciple of apothecia.

Geographical distribution:—So far known from only three locations on Réunion (in two UTM 1× 1 km grid cells, or two UTM 2× 2 km grid cells, Fig. 26A ), on the north-western and southern slopes of the Piton de la Fournaise massif. The three locations are curiously situated near the upper (1865 m) and lower (1085 and 1100 m) limits of the montane belt. Although apparently not widespread on Réunion, this lichen can be quite abundant where it occurs.

Ecology:— Parmotrema mirum is a corticolous species, found on the bark of small branches of trees and shrubs ( Antidesma , Sideroxylon , Tambourissa ) and on a liana stem ( Danais ). It was found in two types of habitat: windward montane rainforest and Pandanus montane wet thicket. According to the pluvial tropical bioclimate and bioclimatic indices of the localities, the species seems to be very ombrophilous [ombrotype belts = upper hyperhumid (Io = 20.6) and ultrahyperhumid (Io = 25.9)], but rather eurythermal [thermotype belts = upper thermotropical (It = 502) and upper mesotropical (It = 345)] ( Fig. 26B ).

Notes:—With its thallus bearing numerous apothecia, its short unciform to bacilliform conidia, its large and thick-walled ascospores, and its medulla with alectoronic acid as a major and constant extrolite, Parmotrema mirum is similar to members of the P. subrugatum group, and especially to P. subrugatum and P. restingense Marcelli, Benatti & Elix (Benatti et al. 2010, Marcelli et al. 2011). The main distinction of P. mirum lies in the constant presence of numerous and conspicuous isidioid outgrowths on the amphithecium and thalline margin, even in young apothecia. The shape, size and branching of these protuberances are rather variable, as is the presence of cilia. These outgrowths have an unconstricted, ± massive base and are most likely not vegetative propagules. In P. subrugatum and P. restingense , amphithecia are smooth when young and rugose and veined with age; only a few short papilloid-isidioid structures are sometimes present on the thalline margin in P. subrugatum (Benatti et al. 2010; first author’s observation). Another discriminating feature is that the apothecial cups of P. mirum develop on constricted stipes, whereas those of P. subrugatum and P. restingense develop on inflated stipes. Parmotrema hanningtonianum (Müll. Arg.) Hale and P. uberrimum (Hue) Hale are two species with amphithecia covered with conspicuous and coarse outgrowths, like P. mirum . However, these taxa produce much smaller ascospores (ca. 15–20 × 8–10 µm), and longer and differently shaped (sublageniform, filiform) conidia, their apothecial stipes are inflated, their lower surfaces are coloured differently, and the medullary chemistry of P. hanningtonianum is different (gyrophoric acid, fatty acids) ( Krog & Swinscow 1981).

Unlike the protuberances always present on amphithecia, the development of isidia on the upper surface of the lobes of P. mirum is much more variable. A substantial proportion of the thalli examined (38%, n = 26) are completely devoid of them. For the isidiate specimens, the abundance of isidia varies from rare to numerous, according to the thalli. In our phylogenetic study based on ITS sequences of four specimens, the three isidiate and the one non-isidiate thalli are grouped in the same monophyletic clade ( Fig. 4 ), supporting the view that only one taxon is involved and that the presence of isidia is a variable character in this species. There is no clear-cut morphological difference between what we have called isidia and the isidioid structures on the amphithecia. The isidia are, however, generally thinner and shorter, and less branched. Both types of structures may occasionally be ciliate.

Two populations of P. mirum are known so far, one located at 1865 m elevation on the northwest slope of the Piton de la Fournaise volcano, the other at 1085–1100 m, on its southern slope.A comparative study of the morphology and anatomy of thalli from these two populations shows that they differ significantly for two characters: the presence/ absence of isidia, and the length of the ascospores ( Table 7). The population located towards the lower limit of the montane rainforest has a higher proportion of isidiate thalli than the one located towards the upper limit (Fisher’s exact test, one-tailed, P = 0.011), and the ascospores produced are on average shorter (Wilcoxon-Mann-Whitney test, one-tailed, U = 5, P = 0.041). It remains to be determined if environmental parameters can explain these phenotypic differences.

In our 3-locus phylogenetic tree, P. mirum and P. mellissii were resolved as a supported group ( Fig. 3 ). In both species, alectoronic acid is the major secondary metabolites of the medulla.

Additional specimens examined (paratypes):— FRANCE. Réunion: Le Tampon, Piton Textor trail, elev. 1865 m, 21°10’44”S, 55°38’11”E, in windward montane rainforest, in an overall north orientation, on the bark of small branches of Tambourissa sp. and Sideroxylon borbonicum , 27 August 2012, D. Masson 974.4092 (LG), 974.4090 (REU), 9744091, 974.4093, 974.4094 (Hb. DM); Saint-Philippe, forêt de Saint-Philippe, Piton Ravine Basse Vallée, GR R2 trail, elev. 1085 m, 21°19’28”S, 55°42’16”E, in Pandanus montane wet thicket, in an overall SSW orientation, on the bark of a dead stem of the liana Danais fragrans , 16 August 2013, D. Masson 974.4268 (Hb. DM); ibid., elev. 1100 m, 21°19’26”S, 55°42’17”E, in windward montane rainforest, in an overall SSW orientation, on the bark of branches of Antidesma madagascariense , 16 August 2013, D. Masson 974.4272–74 (Hb. DM), 974.4275, 974.4276 (LG), 974.4277 (REU).

Specimens studied for comparison:

Parmotrema hanningtonianum .—Trop. Afric. (or.), 2–7° lat. austr., s.d., J. Hannington s.n. (G [image!], holotype).

ANGOLA. Koiembe (Quingenge-Benguela), ad cortices arborum, circ. 1400 m s.m., 21 November 1957, J.B. Damann, C. N. Tavares Lichenes Lusitaniae selecti exsiccati 168 ( US [image!]).

Parmotrema restingense .— BRAZIL. São Paulo: Cananéia, Ilha do Cardoso , restinga da Vila Marujá, sobre ramo fino de arbusto, 20 October 1981, M.P. Marcelli 1759 (B [image!], paratype) .

Parmotrema subrugatum .— BRAZIL. Minas Gerais: Poços de Caldas, on tree branch, 1937, Wilberto s.n. ( REN 000063 ) ; Rio de Janeiro: Serra dos Órgãos, Helmreichen s.n. (M [image!], holotype, isotype) ; Rio Grande do Sul: Sobradinho , 375 m, 29°24’20.2”S, 53°01’25.9”W, open place near the road, 17 July 2003, A.A. Spielmann 360 ( SP [image!]) .

Parmotrema uberrimum .— KENYA. s.l., 1912, Vicomte de Poncins (US [image!], isotype); Eastern Province, Machakos District, lava flow 5 km NW of Kibwezi, 1000 m, February 1974, H. Krog 3K 23/118 (US [image!]) .

Parmotrema cf. negrosorientale Elix & Schumm [as ‘ negrosorientalum ’] (2001: 253) MycoBank no. 546186 Type:— PHILIPPINES. Negros, Negros Oriental Province, Mt Talinis ( Cuernos de Negros ), Lunga Nature Trail between Camp Vendiola

(9°16’N, 123°11’E) and Lake Nailig (9°15’N, 123°10’E), 1170 m, on bark, 10 Aug. 2000, F. Schumm s.n. & U. Schwarz (herb.

Schumm 7521 [image!], holotype). ( Fig. 27 )

Thallus foliose, loosely to moderately adnate, membranaceous to subcoriaceous, up to 10 × 14 cm. Lobes irregular to sublinear, mostly imbricate, more rarely contiguous, 3–11 mm wide, rarely plane, main lobes often broadly concave, sorediate lateral lobes erect, sometimes ± involute, more rarely ± revolute, with margins sinuate in young parts, then crenate to laciniate, mostly ascendant, ciliate ( Fig. 27C ). Cilia black, some with coppery glints (pigment), ± numerous and ± evenly distributed, mostly simple, rarely 1–(2) times branched, ca. 0.03–0.06 mm in diameter at the base, up to 6 mm long. Upper surface pale greenish grey, quite dull; faintly to clearly white-maculate, maculae irregular; smooth to rugulose, occasionally slightly wrinkled, not cracked; sorediate, lacking schizidia, pustules, dactyls, phyllidia and isidia. Soralia generally terminal at the apex of laciniae ( Fig. 27D ), then subcapitate or ± labriform, rarely marginal on lobes and linear ± labriform, very rarely extending slightly submarginally, never laminal. Soredia subgranulose, (30)– 43.2 –(60) µm in diameter (n = 150, from 5 thalli, SD = 7.0 µm), sometimes tinged with orange. Laciniae numerous, particularly in older parts, marginal, often lingulate, sometimes palmate to ± dichotomously branched, almost always apically sorediate, ciliate or not, up to 2 mm wide, 5 mm long. Lobules rare, marginal, ciliate or not, up to 5 × 5 mm. Medulla white, at times orange-tinged in soralia and in older, or damaged, parts. Lower surface smooth, rugulose, or granulate, moderately shiny, duller centrally, black to the margin, or with a buff or chestnut brown erhizinate marginal zone (ca. 1–7 mm wide) at main lobe tips, sorediate laciniae or lateral lobes often with an erhizinate, ivory white or ivory-mottled apical or marginal zone (0.5–3 mm wide) ( Fig. 27D ). Rhizines scattered to moderately dense, unevenly distributed, concolor to the lower surface, sometimes with lighter tip when young, some submarginal rhizines with coppery glints (pigment) near apex, simple, up to 2 mm long. Apothecia absent. Pycnidia rare, submarginal, black. Conidia not found (15 pycnidia investigated).

Chemistry:— Spot tests and fluorescence: upper cortex K+ yellow, UV−; medulla K−, C−, KC+ fleeting purple pink, then orange, P−, UV+ blue-white; pigmented medulla and soredia K+ purple. Secondary metabolites (TLC): upper cortex with atranorin and chloroatranorin; medulla with alectoronic acid (major), α-collatolic acid (major), ± 1–3 unidentified substances (minor/trace), ± skyrin, ± parietin; ± an undetermined ciliary pigment: P1.

Geographical distribution:— Parmotrema negrosorientale is a recently described species previously known only from Mount Talinis in Negros Island, Philippines ( Elix & Schumm 2001, Bawingan et al. 2017). A specimen was collected on Réunion in 1840, but the exact location is unknown. More recently, it was found again at two localities, in two UTM 1× 1 km grid cells (or two UTM 2× 2 km grid cells, Fig. 27A ), on the windward side of the island, at 825 and 870 m a.s.l. This lichen does not seem to be widespread on Réunion, but it can be locally abundant where it occurs. It also occurs on Mauritius, as is attested to by a recent collection by P. Diederich and D. Ertz in the Black River Gorges National Park, between 620 and 660 m a.s.l.

Ecology:—On Réunion, the most recent collections come from two types of habitats, Pandanus submontane wet thicket and windward submontane rainforest, where this lichen grows on the bark of branches of the endemic screw pine Pandanus montanus . Bioclimatic indices (bioclimate pluvial tropical, Fig. 27B ) of the two collection localities suggest that the species is ombrophilous and moderately thermophilous: thermotype belts = upper thermotropical (It = 495 and 510), ombrotype belts = lower hyperhumid (Io = 17.5) and ultrahyperhumid (Io = 24.9). Its ecology seems to be close to that of Parmotrema subcorallinum or P. udisilvestre , two taxa with similar distributions in Réunion. In the Philippines, P. negrosorientale was collected on bark, at elevations of 1170 and 1360 m ( Elix & Schumm 2001). No other ecological data are available in the literature.

Notes:—Three species of Parmotrema share with the Reunionese and Mauritian taxon a medulla containing both alectoronic and α-collatolic acids with, occasionally, skyrin, the presence of true non-pustular soralia, ciliate lobe margins, and a black underside. Parmotrema arnoldii (Du Rietz) Hale mainly differs by its submarginal soralia on revolute lobes or lacinia tips, and its cilia without pink-purple pigment ( Hale 1965a; first author’s observation). Parmotrema rampoddense (Nyl.) Hale , considered a pantropical species extending into temperate areas ( Hale 1965 a, Chen et al. 2005), has been reported in MIOI from Madagascar ( Hale 1965 a, Aptroot 1990). Some marginal cilia of the type specimens from Sri Lanka ( Krog & Swinscow 1981) and those of Brazilian specimens ( Spielmann & Marcelli 2009) contain purple-red pigment(s) reacting K+. These ciliary pigments present in P. rampoddense were identified as fusarubin and anhydrofusarubin lactol in Chinese and Guatemalan collections ( Chen et al. 2005, van den Boom et al. 2007). The R F values of the ciliary pigment P1 found in specimens from the Mascarenes do not match either of these two naphthoquinones, according to Elix & Wardlaw (2001, 2002). Besides, the upper surface of P. rampoddense is emaculate ( Elix 1994, Louwhoff & Elix 1999, Kurokawa & Lai 2001) and soralia are not only marginal, as in the Reunionese and Mauritian taxon, but also laminal [ Krog & Swinscow 1981, image (!) of the isotype in S]. Finally, according to its ITS sequence, a Thai specimen of P. rampoddense (GenBank accession MK722222) does not appear phylogenetically close to specimens collected on Réunion ( Fig. 4 ). While it is unlikely that the material from the Mascarenes belongs to P. rampoddense , it does correspond better to the phenotypically close P. negrosorientale . Sadly, it was not possible to obtain the holotype, or even a paratype, on loan for comparison. The isotype could not be found at CANB (C. Gueidan & J.A. Elix, pers. com.). According to the protologue ( Elix & Schumm 2001) and some images of the type specimens available online (www.fschumm.de, accessed 23 August 2020), the Mascarene taxon and P. negrosorientale share the maculate upper surface, the soralia terminal on laciniae or marginal on involute lobes, and the soredia and medulla sometimes tinged with orange. However, the dehydrocollatolic acid reported as a minor medullary substance in P. negrosorientale was not detected in Réunion and Mauritius samples analysed by TLC, and the presence in P. negrosorientale of K+ reacting ciliary pigment(s) remains to be established. Molecular data on P. negrosorientale are therefore needed to study whether the Mascarene and the Philippine taxa are really conspecific.

A thallus collected on Réunion has some old soralia whose soredia are partially stained orange by parietin. This anthraquinone appears to be very rare in the genus Parmotrema , being reported only once, to our knowledge, in the soralia and an exposed area of the medulla of a specimen of P. deflectens from Tanzania ( Krog & Swinscow 1982). We also found parietin in old soralia of P. subdeflectens . These observations can be considered alongside the fact that, according to our phylogenetic data ( Fig. 3 ), P. cf. negrosorientale from Réunion and P. subdeflectens belong to the ‘subarnoldii group’ clade and are therefore related to P. deflectens , a taxon considered by some authors as a chemotype of P. subarnoldii (e.g. Krog & Swinscow 1981, Swinscow & Krog 1988, Krog 2000).

Specimens examined:— FRANCE. Réunion: without locality, 1840, M.E. Mézières de Lépervanche 38 (PC 0009288 a); ibid., La Plaine des Palmistes, Ligne Deux Mille en Dessous, elev. 870 m, 21°07’00–04”S, 55°39’04– 06”E, in Pandanus submontane wet thicket, in an overall NE orientation, on bark of branches of Pandanus montanus , 23 August 2015 & 18 August 2017, D. Masson 974.4858 (REU), 974.5004–06 (Hb. DM), 974.4987, 974.4998 (LG); Saint-André, forêt de Dioré, elev. 825 m, 20°59’35–36”S, 55°34’55”E, in windward submontane rainforest, on bark of branches of Pandanus montanus , 21 August 2017, D. Masson 974.5056 (REU), 974.5060, 954.5227 (Hb. DM), 974.5059, 974.5061 (LG).

MAURITIUS. Plaines Wilhems District, Black River Gorges National Park, Le Pétrin, 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 18780 & D. Ertz (Hb. P. Diederich) .

Selected specimens studied for comparison:

Parmotrema arnoldii .— FRANCE. Finistère: Huelgoat, forêt de Huelgoat, elev. 110 m, 48°21’41”N, 3°43’45”W, in Atlantic oak-beech wood, on bark of a branch of Quercus petraea , 24 August 2007, D. Masson 64.2530 (Hb. DM). Landes: Moustey, Grande Leyre , elev. 30 m, 44°21’N, 0°46’W, in Atlantic oak wood, on bark of a branch of Quercus robur , 21 November 1997, D. Masson 40.2668 (Hb. DM). Pyrénées-Atlantiques: Aussurucq, massif des Arbailles, col Sorzauqui, elev. 845 m, 43°06’56”N, 0°58’53”W, in sub Atlantic-montane beech wood, on bark of branches of Fagus sylvatica , 03 July 2002, D. Masson 64.2655 (Hb. DM)

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 4. Global tree (best scoring maximum likelihood tree) of Parmotrema based on the fungal ITS barcoding marker. Figure can be enlarged for a better reading of labels. Accessions in black are those retrieved from GenBank on June 2023. Those in red are those produced by the authors for this study. Bootstrap support is indicated on branch when ≥ 70%.

FIGURE 26. Parmotrema mirum. 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: Two mature apothecia with well-developed and ciliate isidioid protuberances on the surface of the thalline exciple (Masson 974.4275); D: Isidia cylindrical to navicular, terete to ± flattened, mostly simple (Masson 974.4274); E: Gross morphology of thallus (holotype). Scale bars:A = 10 km; C, D = 3 mm; E = 10 mm.

FIGURE 27. Parmotrema cf. negrosorientale. 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 974.5061); D: Sorediate lobes with soralia terminal at the apex of laciniae, lower surface of sorediate laciniae ivory-white and erhizinate (Masson 974.5059). Scale bars:A = 10 km; C = 8 mm; D = 3 mm.