Parmotrema odontatum (Hue) 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 : 80-83

Parmotrema odontatum (Hue) D.M. Masson & Sérus. , comb. nov. MycoBank no. 853883

Parmelia odontata Hue (1899: 185) MycoBank no. 397978

Type:— FRANCE. La Réunion [without locality], 1889, frère Rodriguez s.n. ( PC, n.v., holotype, fide Hale 1965a; US [image!], isotype) . ( Fig. 31 )

Thallus foliose, loosely to moderately adnate, coriaceous, up to 14 × 20 cm. Lobes irregular to sublinear, sometimes ± separate or contiguous but generally imbricate, 3–13 mm wide, often ± involute to partly convolute, lobe axils usually rounded, with margins sinuate, crenate or dentate, rather frequently laciniate, fairly often lobulate, eciliate ( Fig. 31C ), often with a black rim. Cilia absent, but exceptionally a few ± clumped rhizines can be located on the black rim at the margin of some lobes and thus resemble cilia. Upper surface pale yellowish grey centrally, more greenish towards the periphery, ± dull, glossier towards lobe tips, faintly to clearly effigurate white-maculate, smooth to rugose, lacking schizidia, pustules, dactyls, isidia, soralia. Laciniae occasional to frequent, mostly on lateral lobes, mainly marginal, rarely also laminal, plane, rarely ± terete, sometimes ± dichotomously or irregularly branched, not brittle, up to 4 mm long and 2 mm wide. Lobules frequent, marginal, up to 7 × 7.5 mm. Medulla white throughout. Lower surface rugulose or granulate, ± shiny, black to the margin, or with a chestnut brown erhizinate marginal zone (ca. 1–4.5 mm wide) at main lobe tips. Rhizines in scattered clusters, black, simple, sometimes furcate, up to 1 mm long. Apothecia frequent, laminal or submarginal ( Fig. 31D ), up to 17 mm in diameter, shortly stipitate on constricted stipes (up to 1.6 mm in diameter), disc imperforate, margin crenate, dentate, occasionally shortly laciniate (up to 1.2 mm long), amphithecium maculate, smooth ( Fig. 31D ), rarely reticulate cracked with age. Ascospores (14)16– 18.4 –21(22) × (7)7.5– 9.2 –11 µm, Q = (1.55)1.57– 2.01 –2.45(2.71), epispore (1)– 1.6 –(2) µm thick, n = 150, from 5 thalli, mean values for each thallus: 17.7 × 8.6, 17.8 × 9.4, 18.5 × 9.3, 18.8 × 8.7, 18.9 × 10.0 µm. Pycnidia common, submarginal, also on laciniae when present, black. Conidia bacilliform (8)9–11(12) × ca. 1 µm.

Chemistry:— Spot tests and fluorescence: upper cortex K+ yellow, UV−; medulla K−, C−, KC + pink, P+ orange, UV−. Secondary metabolites ( TLC): upper cortex with atranorin and chloroatranorin; medulla with protocetraric acid.

Geographical distribution:—The species was described by Hue (1899) from Réunion and so far it is only known from this island. The oldest collection dates from 1840, and since then, Parmotrema odontatum has been found at nine localities in seven UTM 1× 1 km grid cells (or six UTM 2× 2 km grid cells, Fig. 31A ). All recent collections are located at low elevations (50–345 m), at the southwestern end of the island at the bottom of the Piton de la Fournaise volcano. As with P. nemorum , it is likely that this lichen also occurs at other localities with parks and gardens with trees in the windward coastal zone, as these anthropogenic lowland habitats have been under-surveyed by lichenologists visiting the island.

Ecology:— Parmotrema odontatum is a corticolous lichen, found on the trunk, branches or twigs of native or introduced trees and shrubs. This species seems to be restricted to the warm and humid low-lying area, as evidenced by the bioclimatic characteristics of the localities: bioclimate pluvial tropical, with thermotype belt = lower thermotropical (605 ≤ It ≤ 638) and ombrotype belts = from lower to upper hyperhumid (14.5 ≤ Io ≤ 19.9) ( Fig. 31B ). It does not occur within the lowland rainforest remnants themselves (except perhaps high in the canopy?), which are probably too dark, but in more lighted secondary habitats such as the sides of forest roads or tracks, tree plantations and parks.

Notes: Hale (1965a) reduced Parmelia odontata into synonymy with Parmelia disparilis Nyl. [= Parmotrema disparile (Nyl.) Hale ], a poorly circumscribed species described by Nylander (1860) from the island of Nosy Be, northwest of Madagascar ( des Abbayes 1956). According the protologue, des Abbayes (1956: 10–11) comments, our own examination of two collections from northern Madagascar (REN) and a photograph of a syntype in H, Parmotrema disparile has a maculate upper surface, eciliate lobe margins with conspicuous ± canaliculate/corniculate laciniae, apothecial margins without or with laciniae (up to 4 mm long), medium size ascospores [21–25 × 10–12 µm, according to the protologue; (15)16– 18.7 –21.5 × (7)8– 9.2 –10.5 µm, Q = (1.50)1.63– 2.04 –2.45(2.63), epispore (1)– 1.3 –(1.5) µm thick, n = 60, from the two Malagasy thalli], and protocetraric acid in the medulla (one specimen, REN 000038, also has an unknown yellow pigment). Conidia of P. disparile were not described so far. Those of the two Malagasy specimens are faintly sublageniform, sometimes slightly curved, and 5–6 µm long. Thus, P. disparile and P. odontatum have quite similar phenotypes ( Table 9), but P. odontatum does not have long and well-developed canaliculate/corniculate laciniae at lobe margins, the epispore is slightly thicker, and above all, the conidia are different. Hale (1965a) cited three collections of P. disparile from two localities in Mexico. Two of these collections belong to P. cornigerum Kurok. (Kurokawa 2001, Egan et al. 2016), one being the type collection. Study of an isotype of P. cornigerum in REN has shown that this taxon is very similar to P. disparile ( Table 9), and it is unfortunate that Kurokawa did not compare the two taxa in the protologue. Both have a maculate upper surface and amphithecium (‘emaculate’ in the protologue of P. cornigerum ), eciliate lobe margins with conspicuous corniculate laciniae, non-perforate apothecial disk (‘perforate’ in the protologue of P. cornigerum ), and ascospores of similar size.According to the isotype of P. cornigerum investigated, conidia are faintly sublageniform and 6–7 µm long. A molecular investigation of this complex is needed to better understand the relationship between P. disparile , P. odontatum and P. cornigerum .

Some collections from Réunion were initially identified as P. zollingeri (Hepp) Hale (e.g. van den Boom et al. 2011). In his revision of the P. zollingeri group, Elix (1998) found that the isotypes of P. zollingeri contain fumarprotocetraric and succinprotocetraric acids as major medullary substances, whereas P. merrillii (Vain.) Hale and P. overeemii (Zahlbr.) Elix contain protocetraric acid as the only major substance. These two species, however, differ from P. odontatum mainly in their ± ciliate margins, emaculate upper surface, and sublageniform conidia that are 5–7 µm in length ( Louwhoff & Elix 1999). In our phylogenetic tree constructed from ITS sequences ( Fig. 4 ), a Thai accession identified as P. overeemii (GenBank MK722218) does not appear to be closely related to the well-supported clade of P. odontatum .

As demonstrated by phylogenetic analysis of a 3-locus data matrix ( Fig. 3 ), P. odontatum belongs to a well-supported clade, comprising four other species ( P. aurantioreagens , P. mascarenense , P. meiospermum and P. orarium ). According to the distribution data currently available, it is possible that all are endemic to the Mascarene Islands ( Table 1 ).

Specimens examined:— FRANCE. Réunion :: ‘provient de mon jardin où il croissait sur le tronc rugueux d’un acacia’, 1840, M.E. Mézières de Lépervanche 7 ( PC 0009289 ) ; Saint-Philippe , Le Tremblet, elev. 140 m, 21°17’41”S, 55°47’57”E, GR R2 variante trail, kiosque by the road, ca. 20 years old tree plantation, 15 October 2003, U. Schiefelbein 1718 (B) ; ibid., Mare Longue, on road towards Mare Longue nature reserve , elev. 50 m, 21°21’41”S, 55°44’45”E, on tree, 28 September 1996, H. Krog RE16/1 & E. Timdal (O) ; forêt de Mare Longue, Sentier botanique, elev. 240 m, 21°22’S, 55°44’E, trees and shrubs along the road, on unidentified tree, 03 June 2008, P. & B. v.d. Boom 40567 (Hb. P. v.d. Boom); ibid., Mare Longue , route forestière 4, elev. 120 m, 21°21’31”S, 55°44’32”E, on the roadside in a disturbed lowland rainforest, in a general southern orientation, on bark of a trunk of an undetermined young tree, 15 August 2015, D. Masson 974.4655 ( LG) ; ibid., elev. 230 m, 21°21’12”S, 55°44’36”E, on the side of a track in a disturbed lowland rainforest, in a general southern orientation, on bark of twigs of Codiaeum sp. , 15 August 2015, D. Masson 974.4656 (Hb. DM) ; ibid., Basse Vallée , route forestière 36, elev. 345 m, 21°21’14”S, 55°42’20”E, on the roadside in a disturbed lowland rainforest with vanilla cultivation, in a general SE orientation, on bark of a trunk of an undetermined tree, 15 August 2015, D. Masson 974.4651 ( LG) ; ibid., elev. 310 m, 21°21’22”S, 55°42’23”E, on the roadside in a disturbed lowland rainforest with vanilla cultivation, in a general SSE orientation, on bark of a dead branch of an undetermined tree, 16 August 2013, D. Masson 974.4286 (Hb. DM) ; Sainte-Rose, Bois Blanc , elev. 80 m, 21°11’S, 55°49’E, in a garden along a road, on bark of a branch of an undetermined tree, 12 April 2003, D. Masson 974.0288 (Hb. DM) ; ibid., Bois Blanc , route forestière 18, elev. 155–175 m, 21°11’40”S, 55°48’51”E, in a managed lowland rainforest with various woodland plantations, on bark of trunks of undetermined trees, 13 August 2015, D. Masson 974.4627, 974.4632 ( LG) , 974.4629 (Hb. DM).

Specimens studied for comparison:

Parmotrema cornigerum .— MEXICO. Chiapas: El Sumidero canyon, north of Tuxtla Gutiérrez , elev. 1220 m, scrub deciduous forest bordering rim of El Sumidero, on deciduous trees, 21 March 1960, M.E. Hale 20078 & T.R. Soderstrom ( REN 000040 , isotype) .

Parmotrema disparile .— MADAGASCAR. Diana : district d’Ambilobe, vallée de l’Ifasy en aval d’Anaborano, elev. 50–200 m, 1950–1951, H. Humbert s.n. ( REN 000038 , 000039 ) .

Parmotrema zollingeri s. lat. — MEXICO. Chiapas: 50 km west of Tuxtla Gutiérrez on highway 190, elev. 1040 m, deciduous mist forest, on deciduous trees, 18 March 1960, M.E. Hale 19954 & T.R. Soderstrom ( REN 000067 ) ; ibid., road to El Suspiro, 5–7 km north of Berriozábal , elev. 920 m, scrubby deciduous pasture, mist forest, on deciduous trees, 22 March 1960, M.E. Hale 20157 & T.R. Soderstrom ( REN 000068 ) ; ibid., 2 km north of highway 190 on road to Puebla Nueva , west of Chiapas, elev. 1070 m, pine pasture, on deciduous trees, 23 March 1960, M.E. Hale 20186 & T.R. Soderstrom ( REN 000069 ) .

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 31. Parmotrema odontatum. 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 974.4655); D: Apothecia of various ages, with smooth amphithecium, on lobes with eciliate margins (Masson 974.4655). Scale bars: A = 10 km; C = 20 mm; D = 8 mm.