Didymoglossum cuspidatum (Willd.) Ebihara & Dubuisson

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 : 25

15. Didymoglossum cuspidatum (Willd.) Ebihara & Dubuisson ( Ebihara et al. 2006: 236), Fig. 13

Trichomanes cuspidatum Willd. (Willdenow 1810: 499). ≡ Microgonium cuspidatum (Willd.) C.Presl ( Presl 1843: 20). Type :— MAURITIUS. ‘ Grandes forêts des Iles de France’, without date, J.B.G.M. Bory de Saint-Vincent s.n. (lectotype B, BW 20 205010!, here designated; isolectotype P, P00612305 !).

= Trichomanes bojeri Hook. & Grev. ( Hooker & Greville 1829: pl. 155). Type:—‘In sylvis umbrosis, ad arborum truncos, in Insula Mauritii’, without date, D. Bojer s.n. (holotype K, K000435677!).

Short description—Epiphytic or lithophytic; long-creeping filiform rhizomes, rootless and densely covered by dense black trichomes, bearing widely separated pending fronds; fronds sub-sessile or well stipitate, up to 6 cm long, usually less than 3–4 cm long, quite variable and highly polymorphic, glabrous, entire with entire to mostly sinuate margins, to slightly lobed, sub-circular to narrowly deltoid to lanceolate, sometimes linear, with palmate venation, false veins parallel to true veins in addition to a continuous sub-marginal false vein ( Fig. 13E ); 1–10 sori per fertile frond, cylindrical to narrowly campanulate with a slightly dilated mouth and usually immersed in apical distinct lobes when numerous; receptacle short to long-exerted.

Global distribution—Western Indian Ocean (excl. Comores).

Current distribution in Mascarenes— La Réunion, Mauritius, Rodrigues.

Ecology—Opportunistic, epiphytic and lithophytic on various substrates in the understory of rainforests and in wet ravines from low to middle elevations (0–1,300 m). The species is usually abundant in lowland rainforests, but is rarer and mostly located in wet ravines in montane rainforests. This is the single Hymenophyllaceae species present on Rodrigues, in a single wet ravine.

Specimens examined—‘Ile de Mascareigne’, without locality, 1831, C. Bélanger s.n. (P00612306).

— MAURITIUS. Bel Ombre , October 2010, S. Hennequin et al. 383 ( MAU 0008184 , P02432448 ) ; Fayence Mt. , December 2007, K. Pynee et al. s.n. ( MAU 0008189 ) ; Rambouillet , April 2011, K. Pynee s.n. ( MAU 0008209 ) ; Alma Hill , September 2012, K. Pynee et al. s.n. ( MAU 0008224 ) ; Bar Le Duc , August 2011, K. Pynee et al. s.n. ( MAU 0009100 ) ; Trou aux Cerfs, October 2015, K. Pynee et al. s.n. ( MAU 0011483 ) ; Mare Longue , October 2010, S. Hennequin et al. 361 ( MAU 0011513 , P02432425 ) .

— LA RÉUNION. Without locality, without date, J. M. C. Richard 122 ( P00065001 ) ; Ilet Alcide , November 2004, F. Rakotondrainibe et al. 6897 ( P00411902 ) .

Note—This widespread species is readily distinguished from the other Didymoglossum species in Mascarenes by its glabrous fronds. Its distinctiveness outside the Mascarenes is discussed in Saïd et al. (2017).

Figures

FIGURE 13. Didymoglossum cuspidatum (Willd.) Ebihara & Dubuisson.A. Typical sub-circular, and lanceolate to deltoid sterile forms as usually observed (La Réunion, ‘Mare Longue’). B. Linear sterile forms (La Réunion, ‘Grand Etang’). C. Ovate to lanceolate fertile fronds with apical sori (La Réunion, ‘Forêt de Bon Accueil, Les Makes’). D. Narrowly lanceolate fertile frond with apical sori (La Réunion, ‘Grand Etang’). E. Small sub-circular/ovate fertile frond with a single sorus, showing sub-marginal false vein (mfv) and false veins parallel to true veins (fv) (photographs.A–D: J.-Y. Dubuisson; E: L. Bauret).