Parmotrema aurantioreagens 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 : 20-22

Parmotrema aurantioreagens D.M. Masson & Sérus. , sp. nov. MycoBank no. 853865

Diagnosis. Shares with P. explanatum (Hale) Hale the barbatic acid chemosyndrome, a rare medullary chemistry in the genus Parmotrema , but differs chiefly by the presence of marginal cilia, soralia, a maculate upper surface and the corticolous habit.

Holotype:— FRANCE. Réunion: Sainte-Suzanne, les Hauts de la Perrière , elev. 765 m, 20°58’44”S, 55°33’52”E, in disturbed windward submontane rainforest in overall NE orientation, on roadside, on bark of a branch of an undetermined tree, 11 August 2015, D. Masson 974.4598 (MNHN-PC-PC0088068).

GenBank accession numbers: ITS ( PP 840413), mtSSU ( PP 842550), EF1-α ( PP 852812).

( Fig. 7 )

Thallus foliose, loosely adnate, membranaceous, ca. 12 × 8 cm (thallus fragmented). Lobes irregular, imbricate, 5–11 mm wide, irregularly wrinkled, sometimes convolute, with margins undulating, crenate to laciniate when sorediate, rarely lobulate, ciliate ( Fig. 7E ). Cilia black, unevenly distributed ( Fig. 7C ), simple, very rarely 1–2 times branched, ca. 0.04–0.05 mm in diameter at the base, up to 3 mm long. Upper surface pale greenish grey, mat or slightly shiny, faintly to clearly effigurate white-maculate, slightly wrinkled, rarely smooth, sometimes cracked in the older parts, sorediate, lacking schizidia, pustules, dactyls, phyllidia and isidia. Soralia marginal at the tip of short laciniae ( Fig. 7D ), occasionally somewhat labriform. Soredia subgranulose, (30)– 42.3 –(60) µm in diameter (n = 30, from 1 thallus, SD = 7.7 µm). Lobules occasional, marginal, up to 2 × 2.5 mm. Medulla white throughout. Lower surface smooth or granulose, rather dull in the central part, shiny in the periphery, black to the margin, or with an ochraceous-buff erhizinate marginal zone (ca. 1–3.5 mm wide) at main lobe tips; sorediate laciniae often ivory mottled ( Fig. 7D ). Rhizines ± in clusters, sometimes rather dense, concolor to the lower surface, often with pale tip when young, simple, rarely 1–2 times branched, slender, heterogeneous in size, up to 2.5 mm long. Apothecia not present. Pycnidia not present. Upper cortex palisade plectenchymatous, not fragile, (9)– 14.2 –(25) µm thick. Algal layer discontinuous, (0)– 17.0 –(30) µm thick. Medulla (67)– 77.0 –(83) µm thick. Lower cortex prosoplectenchymatous, (11)– 14.2– (17) µm thick.

Chemistry:— Spot tests and fluorescence: upper cortex K+ yellow, UV−; medulla K−, C + orange, KC + orange, P−, UV± bluish-white. Secondary metabolites ( TLC): upper cortex with atranorin and chloroatranorin; medulla with barbatic acid (major), 4- O -demethylbarbatic acid (major), and obtusatic acid (trace).

Etymology:—The specific epithet refers to the orange reaction of the medulla produced by the C and KC spot tests.

Geographical distribution: —So far known from a single locality on Réunion Island, at an elevation of 765 m, on the northern slope of the Piton des Neiges massif ( Fig. 7A ).

Ecology:—The species was found on the bark of a branch of an undetermined tree, on the side of a road through a degraded windward submontane rainforest covering a northeastern facing slope. Various alien plants invaded this forest, mainly Strawberry Guava ( Psidium cattleianum Afzel. ex Sabine ). The bioclimate of the locality is pluvial tropical, thermotype belt = upper thermotropical (It = 500), ombrotype belt = lower hyperhumid (Io = 16.2) ( Fig. 7B ).

Notes:— Parmotrema aurantioreagens is primarily characterized by its medullary chemistry, which is uncommon in the genus Parmotrema . Only one other species, P. explanatum , has both barbatic and 4- O -demethylbarbatic acids as major substances ( Hale 1965b, label of the isotype kept in the US herbarium). However, P. explanatum lacks marginal cilia, vegetative propagules, and maculation on the upper surface, and its medulla is twice as thick ( Hale 1965b). Parmotrema insuetum (Kurok.) Hale , P. matudae (Kurok.) Hale ex DePriest & B.W. Hale and P. neodiffractaicum R.S. Egan are also sorediate species with barbatic acid in the medulla, but they are eciliate, emaculate, and they all contain diffractaic acid as the major substance, not 4- O -demethylbarbatic acid ( Kurokawa 1984, Louwhoff & Elix 1999, Egan et al. 2016).

As demonstrated by our phylogenetic analysis of a 3-locus data matrix ( Fig. 3 ), Parmotrema aurantioreagens belongs to a supported clade, comprising two other species either described as new in this paper ( P. mascarenense ) or already described ( P. meiospermum ). All three are possible endemics to the Mascarenes.

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 7. Parmotrema aurantioreagens. A: Distribution on Réunion (UTM 2×2 km grid system); B: Bioclimatic characteristics of collection site (abbreviations and threshold values for thermotype and ombrotype horizons from Rivas-Martínez et al. 2011: 17–18); C: Upper surface of lobes with marginal cilia unevenly distributed (holotype); D: Sorediate lobe with marginal soralia at the tip of short laciniae, and margin of lower surface mottled with ivory white (holotype); E: Gross morphology of thallus (holotype). Scale bars: A = 10 km; C = 5 mm; D = 4 mm; E = 10 mm.