Parmotrema reunionicum D.M. Masson

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 : 94-97

Parmotrema reunionicum D.M. Masson , sp. nov. MycoBank no. 853878

Diagnosis. Shares with Parmotrema inexspectatum (Abbayes ex Krog & Swinscow) D.M. Masson comb. nov. and P. lambinonii Sérus. the same rare medullary chemistry (colensoic acid-lividic acid chemosyndrome), but differs from them mainly by the presence of true soralia.

Holotype:— FRANCE. Réunion: Sainte-Marie, Plaine des Fougères , between Ravine Sèche and Ravine Mère Canal, elev. 1220 m, 20°58’29”S, 55°31’04”E, in windward montane rainforest, in an overall NE orientation, on bark of Pandanus montanus , 17 April 2003, D. Masson 974.0446 (MNHN-PC-PC0088081; isotype: LG).

( Fig. 36 )

Thallus foliose, loosely to moderately adnate, membranaceous to subcoriaceous, up to 6 × 9 cm. Lobes irregular, imbricate, 3–10 mm wide, rarely plane but mostly concave, rarely convolute, with margins undulated, crenate to somewhat shortly laciniate when sorediate, very rarely lobulate, often ascendant, ciliate ( Fig. 36E ). Cilia conspicuous, black, some with coppery glints (pigment), abundant, mostly simple but sometimes 1–2 times dichotomously branched, ca. 0.04–0.06 mm in diameter at the base, up to 5 mm long. Upper surface pale yellowish grey, rather dull, emaculate or faintly punctiform white-maculate, smooth or slightly wrinkled in the older parts, sorediate, lacking schizidia, pustules, dactyls, phyllidia and isidia. Soralia marginal, at first linear interrupted or at the tip of very short laciniae, then coalescent and forming ± rounded clusters ( Fig. 36C ); very rarely submarginal, and then subcapitate ( Fig. 36D ). Soredia subgranulose to granulose, (35)– 48.8 –(65) µm in diameter (n = 90, from 3 thalli, SD = 6.0 µm). Lobules very occasional, marginal, up to 1.5 × 2 mm. Medulla white throughout. Lower surface smooth or slightly rugulose, rather dull in the central part, more shiny towards the periphery, black to the margin, or with a chestnut brown or buff erhizinate marginal zone (ca. 0.5–5 mm wide) at main lobe tips. Rhizines scanty, in clusters, concolor to the lower surface, frequently with white tip when young, some marginal with coppery glints, simple or 1–2(3) times branched, up to 2.5 mm long. Apothecia absent. Pycnidia rare, submarginal towards apices; only primordia seen. Conidia not found. Upper cortex palisade plectenchymatous, not fragile, (15)– 20.2 –(30) µm thick. Algal layer continuous or discontinuous, (10)– 18.0 –(30) µm thick. Medulla (47)– 76.1 –(115) µm thick. Lower cortex prosoplectenchymatous, (15)– 17.6– (22) µm thick.

Chemistry:— Spot tests and fluorescence: upper cortex K+ yellow, UV−; medulla K+ slowly pinkish brick-red, C−, KC + fleeting violet then brick-red, P± pale orange, UV+ white. Secondary metabolites ( TLC): upper cortex with atranorin and chloroatranorin; medulla with colensoic acid, hydroxycolensoic and/or norcolensoic acid, 4-Omethylphysodic acid, 4-O-methyllividic acid, physodic acid, lividic acid, oxyphysodic acid and two unidentified substances; ± an undetermined ciliary pigment: P1.

Etymology:—Named after Réunion where this species was discovered.

Geographical distribution:—So far known from two collections gathered nine years apart at the same locality, at an elevation of 1220 m on the northern side of the Piton des Neiges massif, on Réunion ( Fig. 36A ).

Ecology:—The collected thalli grew on ± mossy bark of Pandanus montanus , in a windward montane rainforest covering a northeastern facing slope. The bioclimatic features of the locality are: bioclimate = pluvial tropical, thermotype belt = lower mesotropical (It = 452), ombrotype belt = lower hyperhumid (Io = 16.0) ( Fig. 36B ).

Notes:—Whereas it is frequently found in species of the genus Hypotrachyna , the lividic acid chemosyndrome is very rare in the genus Parmotrema ( Hale 1973, Sérusiaux 1984). Until now, it was only known in three African taxa: Parmotrema inexspectatum [see nomenclatural and taxonomic comment below], P. lambinonii and P. paradoxum (Hale) Hale. Parmotrema inexspectatum and P. paradoxum lack vegetative propagules and usually produce apothecia. They have been reported from Côte d’Ivoire ( des Abbayes 1958, Hale 1965a) and Uganda ( Hale 1973, Krog & Swinscow 1981). Parmotrema lambinonii produces laminal and submarginal pustules that erupt without forming typical soredia. It was collected in Democratic Republic of the Congo and in Rwanda ( Sérusiaux 1984). A third species, P. menyamyaense Louwhoff & Elix , has a rather similar medullary chemistry, but without lividic acid and with eumitrin pigments ( Louwhoff & Elix 1999). Like P. inexspectatum and P. paradoxum , it lacks vegetative propagules, but its ascospores are smaller. It was previously known only from Papua New Guinea. However, it appears that this taxon is also present in the Indian Ocean indeed, the Parmelia subrugata Kremp. cited by des Abbayes (1956) from Mohéli Island in the Comoro Archipelago is a Parmotrema menyamyaense , according to its morphology, medullary chemistry and ascospore size [(19)19.5– 21.6 –23.5 × 11.5– 12.4 –13.5 µm, epispore 2–2.5 µm thick, n = 30]. It is unfortunately not yet possible to elucidate the relationship between P. inexspectatum , P. lambinonii , P. menyamyaense , P. paradoxum and P. reunionicum , notably due to the lack of phylogenetic information. We have not been able to study the DNA of the P. reunionicum specimens, despite two attempts.

Nomenclatural and taxonomic comment:— Parmelia inexspectata was described by des Abbayes in Bulletin de l’Institut français d’Afrique noire A 20(1): 16, 1958. The material cited by des Abbayes consists of two specimens that are currently in REN with the reference numbers 000046 and 000047. According to the labels handwritten by des Abbayes, both specimens were collected from the same locality ( Côte d’Ivoire, mont Tonkoui, cercle de Man, 1150 m) but on two different substrates (‘tronc d’arbre dans la forêt à Parinari excelsa ’ for REN 000046, ‘troncs de jeunes Quinquinas’ for REN 000047), and on two different dates (17 Oct. 1951 for REN 000046, 16 Oct. 1951 for REN 000047). REN 000047 has ‘TYPUS’ handwritten on the packet. A duplicate of REN 000047, probably sent by des Abbayes to Hale between 1958 and 1965 and with a typewritten label in Latin, is also present in US. In the protologue published in 1958, des Abbayes unfortunately did not indicate which of these collections was the type; consequently, the name proposed by him is not validly published (Art. 40.1). To our knowledge, Krog & Swinscow (1981) were the first to validate the name: (1) they accepted the name, (2) they clearly cited the relevant page in the 1958 publication, thereby providing the necessary reference to a previous effectively published description (Art. 38.1) and (3) they clearly indicated a single collection (the one kept in US) that they considered to be the type. In the same publication, Krog & Swinscow synonymised Parmelia paradoxa Hale Phytologia 27: 1, 1973, described from Uganda, with P. inexspectata Abbayes , from Ivory Coast. This synonymy was also mentioned by Hale & DePriest (1999). If the two taxa are indeed conspecific, Parmelia paradoxa Hale would be the earlier validly published name for the species concerned. However, according to the literature and our own observations ( Table 11), the relationship between the two taxa appears rather confusing. In addition, two Malagasy specimens with a phenotype close to that of Parmotrema inexspectatum and P. paradoxum cannot be confidently assigned to either species. The available data seem insufficient to clarify the taxonomy of the African Parmotrema with ciliate lobe margins, an emaculate upper surface, no vegetative propagules, an imperforate apothecial disc, large spores and a medulla with the lividic acid complex.

When Hale (1974a) transferred Parmelia inexspectata to Parmotrema , he used the invalid ‘basionym’ citing des Abbayes (1958), and hence Hale’s combination is not validly published, either as a combination or as the name of a new taxon. We have not found any validation of the name Parmotrema inexspectatum published after 1974, so it is necessary to make a new combination:

Parmotrema inexspectatum (Abbayes ex Krog & Swinscow) D.M. Masson , comb. nov. MycoBank no. 853924

Basionym: Parmelia inexspectata Abbayes ex Krog & Swinscow, Bull. Br. Mus. nat. Hist. (Bot.), 9(3): 188, 1981. MycoBank no. 853923

Type :— CÔTE D’IVOIRE. In Monte Tonkoui , prope Man , ad truncum Cinchonae, 1150 m, 16 October 1951, H. des Abbayes s.n. (US, holotype; REN 000047, isotype) .

Additional specimen examined (paratype):— FRANCE. Réunion: Sainte-Marie, Plaine des Fougères , between Ravine Sèche and Ravine Mère Canal, elev. 1220 m, 20°58’29”S, 55°31’04”E, in windward montane rainforest, in an overall NE orientation, on ± mossy bark of a branch of Pandanus montanus , 30 August 2012, D. Masson 974.4124 (Hb. DM) .

Specimens studied for comparison:

Parmotrema inexspectatum .— CÔTE D’IVOIRE. Man District : Mont Tonkoui , elev. 1150 m, troncs de jeunes Quinquinas, 16 October 1951, H. des Abbayes s.n. ( REN 000047 , isotype); ibid., tronc d’arbre dans la forêt à Parinari excelsa , 17 October 1951, H. des Abbayes s.n. ( REN 000046 , paratype) .

Parmotrema lambinonii .— DEMOCRATIC REPUBLIC OF THE CONGO. Massif du Kahuzi, piste Mukaba (ancienne route Kavumu-Kahuzi), km 17, elev. 2210 m, forêt de Bambous, sur le sommet de bambous inclinés, en lisière de la piste, 24 December 1971, J. Lambinon 71/Z/1195 (LG, holotype); Massif du Kahuzi, en bordure du marais Musisi, à proximité de la route Bukavu-Walikale, elev. 2180 m, taillis dense à Kotschya cf. africana , Hypericum revolutum , Agauria salicifolia …, sur petites branches tombées (généralement Kotschya ), 22 December 1971, J. Lambinon 71/Z/1149 (LG, paratype).

RWANDA. Forêt de Rugege , partie W du marais Kamiranzovu, elev. ca. 1950 m, sur branches moussues de Syzygium mourant, 18 August 1974, J. Lambinon 74/928 ( LG, paratype) .

Parmotrema menyamyaense . — COMOROS. Mohéli: massif de Mafondrodjo [= Mafoumboudjou], elev. 620 m, July 1945, unknown collector ( REN 000064 ) .

Parmotrema sp. — MADAGASCAR. Diana : Montagne d’Ambre, elev. 1100 m, branches d’arbre en forêt, 29 October 1956, H. des Abbayes 3119 ( REN 000065 ); ibid., Montagne d’Ambre, poste des Roussettes, elev. 1000 m, sur Quinquina, 31 October 1956, H. des Abbayes 3144 ( REN 000066 ) .

Figures

FIGURE 36. Parmotrema reunionicum. 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: Sorediate lobes with marginal soralia, at first ± linear interrupted or at the tip of very short laciniae, then coalescent and forming ± rounded clusters (holotype); D: Sorediate lobe with some subcapitate submarginal soralia (holotype); E: Gross morphology of thallus (holotype). Scale bars:A = 10 km; C = 3 mm; D = 2 mm; E = 10 mm.