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 Author Masson, Didier 0000-0002-3340-5472 Vertevoye, 2860 route d’Irieu, F- 40390 Saint-Martin-de-Seignanx, France di. masson @ wanadoo. fr; https: // orcid. org / 0000 - 0002 - 3340 - 5472 di.masson@wanadoo.fr Author Magain, Nicolas 0000-0001-5409-9518 Evolution and Conservation Biology, InBios research centre, Sart Tilman B 22, Quartier Vallée 1, Chemin de la vallée 4, B- 4000 Liège, Belgium nicolas. magain @ uliege. be; https: // orcid. org / 0000 - 0001 - 5409 - 9518 nicolas.magain@uliege.be Author Sérusiaux, Emmanuël 0000-0002-3340-5472 Vertevoye, 2860 route d’Irieu, F- 40390 Saint-Martin-de-Seignanx, France di. masson @ wanadoo. fr; https: // orcid. org / 0000 - 0002 - 3340 - 5472 & Evolution and Conservation Biology, InBios research centre, Sart Tilman B 22, Quartier Vallée 1, Chemin de la vallée 4, B- 4000 Liège, Belgium e. serusiaux @ uliege. be; https: // orcid. org / 0000 - 0002 - 0456 - 0131 * Corresponding author & Vertevoye, 2860 route d’Irieu, F- 40390 Saint-Martin-de-Seignanx, France di. masson @ wanadoo. fr; https: // orcid. org / 0000 - 0002 - 3340 - 5472 di.masson@wanadoo.fr text Phytotaxa 2024 2024-06-27 657 1 1 138 http://dx.doi.org/10.11646/phytotaxa.657.1.1 journal article 10.11646/phytotaxa.657.1.1 1179-3163 13217474 Parmotrema praesorediosum (Nyl.) Hale (1974a: 338) MycoBank no. 343106 Parmelia praesorediosa Nyl. (1891: 18) MycoBank no. 398093 Type :— SINGAPORE . [without locality], 30 November 1879 , E. Almquist s.n. (H-NYL 35547 [image!], holotype ; S [image!] isotype ; fide Hale 1965a ) . ( Fig. 34 ) Thallus foliose, moderately adnate to adnate, membranaceous to subcoriaceous, up to 8 cm in diameter. Lobes rounded, usually imbricate, rarely contiguous, irregularly branched, 2–7 mm wide, rarely plane but most often slightly concave, with margins undulated, ascendant, smooth or irregularly crenate, eciliate ( Fig. 34C ). Upper surface greenish grey, emaculate, dull, smooth near lobe tips but slightly wrinkled in the older parts, sorediate, lacking schizidia, pustules, dactyls, lobules, phyllidia and isidia. Soralia linear marginal at first, next labriform and crescent-shaped ( Fig. 34D ), rarely submarginal and then subcapitate. Soredia subgranulose, (30)– 42.5 –(60) µm in diameter (n = 60, from 2 specimens , SD = 6.9 µm). Medulla white throughout. Lower surface rugulose and mat, black in the central part, turning brown towards the margins, naked marginal zone (ca. 1–2.5 mm wide) buff, or whitish under some sorediate lobes. Rhizines moderately dense, irregularly distributed, concolor to the lower surface, frequently with white tip when young, simple, rarely furcate, short (up to 0.5 mm long). Apothecia absent. Pycnidia absent. Chemistry :— Spot tests and fluorescence : upper cortex K+ yellow, UV−; medulla K− or K± yellow, C− , KC− , Por P+ yellowish, UV−. Secondary metabolites ( TLC ): upper cortex with atranorin and chloroatranorin; medulla with 2−3 undetermined fatty acids (Rf classes:A2−4, B3−4, C 3−5), ± atranorin. Geographical distribution :—A pantropical species ( Hale 1965a , Louwhoff 2001 ) that extends into some warm-temperate areas ( Kurokawa 2006 , Hodkinson & Case 2008 ). In MIOI, present in Madagascar ( des Abbayes 1961 , Aptroot 1991) and in Réunion (van den Boom et al . 2011). Not reported from Mauritius by Diederich & Ertz (2020), but 15 specimens from seven localities, collected by Krog & Timdal in 1991 and determined as Parmotrema praesorediosum , are in O ( GBIF 2022a ). On Réunion , the taxon was collected at one documented locality ( Fig. 34A ) and one undetermined locality. Ecology :—According to the literature, Parmotrema praesorediosum is corticolous or saxicolous (e.g. Krog & Swinscow 1981 , Elix 1994 , Divakar & Upreti 2005 ). On trees, the species can grow on twigs, branches, as well as on trunks ( Martins & Marcelli 2011 ). It is found at low elevations in fairly dry, generally well-lit sites, often in areas disturbed by human activity, where it is sometimes considered a weedy species ( Hale 1965 a , Smith 1993, Elix 1994 , Lai 2001 , Bungartz & Spielmann 2019 ). The species can be found on wind-exposed trees growing near the sea ( Marcelli 1991 ); this is the case on Réunion at the only documented locality where P. praesorediosum was collected on smooth bark of several Pandanus utilis growing in a recreational area just near the sea. The bioclimatic features of this locality are: bioclimate: pluvial tropical, thermotype belt: lower thermotropical (It = 660), ombrotype belt: upper humid (Io = 11.8) ( Fig. 34B ). Notes :—The two major aliphatic acids occurring in the medulla of Parmotrema praesorediosum were described as praesorediosic and protopraesorediosic by David et al . (1990) . We were unable to identify these two acids with any certainty in the Reunionese specimens, as the TLC performed did not allow us to differentiate them from those of the constipatic acid group. Spot tests with K applied to the medulla and soralia of the specimens collected gave results ranging from a distinctly yellow colour to no reaction ( Table 10 ), suggesting the occurrence of atranorin in variable concentrations in these anatomical structures. Hale (1971a) distinguished P. mordenii (Hale) Hale from P. praesorediosum by its substrate ecology (saxicolous vs corticolous), the presence (vs absence) of atranorin in the medulla, and by some minor morphological differences (size of the lobes, size of the soredia, morphology of the soralia). In East Africa, Krog & Swinscow (1981) found no clear difference in medullary reactions and morphology between corticolous and saxicolous specimens, and therefore reduced P. mordenii to synonymy with P. praesorediosum . Some later authors did not accept their proposal (e.g. Spielmann & Marcelli 2009 , Benatti & Marcelli 2010 b , Gerlach & Eliasaro 2012, Bungartz & Spielmann 2019 ), mainly because of the presence of atranorin in the medulla of P. mordenii , a feature considered diagnostic by these authors. The concentration of atranorin in the cortex of lichen thalli, including Parmotrema , was shown to vary with environmental factors (e.g. Armaleo et al. 2008 , Shukla et al . 2015 ). The same may be assumed for medullary atranorin, which could explain the variability observed in Reunionese material, even between corticolous specimens ( Table 10 ). Evidence of the existence of P. mordenii on Réunion is further complicated by the uncertainty surrounding the identity of the fatty acids present in its medulla. Hale (1971a) , Nash & Elix (2002) and Nash et al . (2016) reported caperatic and protolichesterinic acids. Marcelli & Benatti (2010) and Benatti (2014) reported caperatic, protolichesterinic, praesorediosic, protopraesorediosic and two undetermined acids. Flakus et al . (2014) reported the constipatic acid group, and Bungartz & Spielmann (2019) cited praesorediosic and protopraesorediosic acids. We were unable to identify the 2−3 fatty acids present in the Reunionese material by TLC, but they are neither caperatic acid nor protolichesterinic acid. We echo Benatti’s (2014) conclusion that indepth morpho-anatomical, chemical, molecular and ecological studies are needed to clarify the relationship between P. praesorediosum and P. mordenii . Lacking such studies, all the material collected on Réunion is assigned to P. praesorediosum . Unfortunately, we have not been able to study the DNA of specimens from Saint-Benoît, despite two attempts. Specimens examined: — FRANCE . Réunion : Saint-Benoît, Pointe du Bourbier, elev. 20 m , 21°01’13”S , 55°42’13”E , coastal recreational area with many Pandanus utilis , on bark of P. utilis , 11 June 2008 , P. & B. van den Boom 40992 ( Hb. van den Boom); ibid ., 12 August 2013 , D. Masson 974.4214 , 974.4215 (Hb. DM); without locality, April 1989 , G. Follmann & I. Follmann-Schrag s.n. (B). FIGURE 34. Parmotrema praesorediosum . 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 : Gross morphology of thallus ( Masson 974.4214 ); D : Sorediate lobes, with ± labriform and crescent-shaped marginal soralia ( Masson 974.4215 ). Scale bars: A = 10 km; C = 10 mm; D = 3 mm. TABLE 10. Colour reactions with potassium hydroxide of the medulla and soralia of corticolous and saxicolous specimens of Parmotrema praesorediosum from Réunion .

Specimens	medulla	Spot tests	soralia	Substrate ecology
Masson 974.4215	K−	K−	corticolous
Masson 974.4214	K+ faint yellow	K+ faint yellow	corticolous
van den Boom 40992	K+ faint yellow	K+ yellow	corticolous
G. Follmann s.n.	K+ yellow	K+ yellow	saxicolous

Specimen studied for comparison :— FRANCE . Guadeloupe : Basse-Terre, Sainte-Rose, Morne Rouge, elev. 3 m, on Avicennia germinans in a mangrove, 27 October 1992 , J. Vivant s.n. (Hb. DM).