Hymenophyllum peltatum (Poir.) Desv.

Dubuisson, Jean-Yves, Pechon, Timothée Le, Bauret, Lucie, Rouhan, Germinal, Reeb, Catherine, Boucheron-Dubuisson, Elodie, Selosse, Marc-André, Chaussidon, Cécile, Dajoz, Isabelle, Pynee, Kersley, Grangaud, Edmond, Robert, Yannis, Tamon, Jean- Maurice & Hennequin, Sabine, 2018, Disentangling the diversity and taxonomy of Hymenophyllaceae (Hymenophyllales, Polypodiidae) in the Mascarene archipelago, with ecological implications, Phytotaxa 375 (1), pp. 1-58 : 29

16. Hymenophyllum peltatum (Poir.) Desv. ( Desvaux 1827: 333), Fig. 14C, D

Trichomanes peltatum Poir. ( Poiret 1808: 76), non Baker ( Baker 1867: 336, 337, t. 8, fig. C) ≡ Meringium peltatum (Poir.) Copel. ( Copeland 1938: 98). Type:— MAURITIUS. ‘Ile de France’, without date, J.B.G.M. Bory de St.-Vincent s.n. in herb. Du Petit-Thouars (lectotype P, P00789570!, inadvertently designated by Tindale (1963); isolectotype LE, LE00007981!).

= Hymenophyllum unilaterale Bory ex Willd. (Willdenow 1810: 522). Type :— LA REUNION. ‘ Rochers humides à 1000 toises Bourbon’, without date, J.B.G.M. Bory de St-Vincent s.n. (lectotype B, BW 20 225010!, here designated; isolectotypes FI, FI003711 !, P, P00477834 !). Note: It is highly possible that these specimens collected by Bory and here considered by Willdenow are part of the same gathering as those considered by Poiret for Trichomanes peltatum (see above), as it seems to be indicated in a label on the sheet of the LE00007981 specimen. Accordingly, this name would be illegitimate.

= Hymenophyllum menziesii C.Presl ( Presl 1843: 51). ≡ Hymenophyllum peltatum (Poir.) Desv. var. menziesii (C.Presl) C.Chr. ( Christensen 1940: 6). Type:— ARGENTINA. Isla de los Estados, ‘Habitat in Staatenland’, before 1842, A. Menzies s.n. (holotype E, E00215323!).

= Hymenophyllum uncinatum Sim ( Sim 1915: 81). Type:—SOUTH-AFRICA. ‘Tafelberg, XII 1891 ’, T. Kässer 1007 (holotype PRE, PRE0085675 !; isotype PRE, PRE0592122 !).

Short description—Epiphytic or lithophytic; long-creeping filiform rhizomes, bearing sparsely distributed roots and rare reddish-brown trichomes, and widely separated pending fronds; fronds glabrous, with narrowly winged stipes and rachises, up to 20 cm long, sometimes longer but mostly less than 15 cm long, narrowly lanceolate to oblong, sometimes linear, pinnate-pinnatifid, with toothed margins ( Fig. 14D ); numerous sori, paratactic, usually on the acroscopic mostproximal pinnules, bilabiate with a small base and with entire (not toothed) margins; receptacle included.

General distribution—Tropical and subtropical Africa, western Indian Ocean, subantarctic islands (Crozet, Kerguelen, Marion, Prince Edward), Tristan da Cunha, Andes from Venezuela to southern South-America (Patagonia and neighboring islands). The precise distribution in neotropics is detailed in Kessler & Smith (2017).

Current distribution in Mascarenes— La Réunion.

Ecology—Epiphytic on tree-trunks or lithophytic on wet rocks in montane rainforests and at high elevations up to the treeline (1,350 –1,900 m).

Representative specimens examined— LA RÉUNION. Without locality, without date, Maire s.n. ( P01324708 ) ; Cilaos, February 1969, T. Cadet 2044 ( P01324711 ) ; Notre Dame de la Paix, June 2006, E. Grangaud 1756 ( P01324717 ) .

Note—This species is more widespread in temperate wet regions at low elevations, explaining why it is observed at high elevations in the tropics in ‘temperate’ or ‘fresh’ ecosystems. It can easily be confused with the sub-cosmopolitan H. tunbrigense (L.) Sm. (Smith 1794: pl. 162), absent in the Mascarenes and with a questionable presence on Madagascar. It differs by the sorus margin, which is entire in H. peltatum and toothed in H. tunbrigense . The accurate distribution of H. peltatum remains to be assessed, as molecular studies have shown that the La Réunion specimens do not group with neither Australasian specimens ( Hennequin et al. 2010; del Rio et al. 2017) nor with South American ones ( Larsen et al. 2013).

Figures

FIGURE 14. A. Hymenophyllum fumarioides Bory ex. Willd, as epiphyte (La Réunion, ‘Mare Longue’). B. H. fumarioides, detail of curled/crisped segments and sori with toothed margins. C. H. peltatum (Poir.) Desv., as epiphyte (La Réunion, ‘Pitons Mare à Boue’). D. H. peltatum, detail of toothed/serrulate laminar margins. E. H. sibthorpioides (Bory ex Willd.) Mett. ex Kuhn, as epiphytic (La Réunion, ‘Vallée Heureuse’). F. H. sibthorpioides, fertile frond and sori with toothed margins (photographs. A, E: C. Chaussidon; B, F: L. Bauret; C: J.-Y. Dubuisson; D: J.-M. Tamon).