Didymoglossum barklyanum (Baker) J.P.Roux

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 : 24-25

13. Didymoglossum barklyanum (Baker) J.P.Roux ( Roux 2009: 41), Fig. 12A

Trichomanes barklyanum Baker ( Baker 1867: 338, t. 8, fig. F), as ‘ barklianum ’. Type:— MAURITIUS. ‘Tamari cascade’, without date, H. Barkly & A.M. Barkly s.n. (holotype K, K000228376!; isotype P, P00477822!). Note: in the introduction of his article including the description of T. barklyanum, Baker (1867) clearly mentioned that all the specimens are housed in the Kew collections (K). This allows treating the specimen at K as the holotype.

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 with short stipes, up to 1.5 cm long, narrowly ovate to oblong, entire with entire to mostly sinuate margins, with pinnate venation, lacking false veins, hairy with dark, not pedonculated, and usually paired trichomes on the margin; a single terminal sorus per fertile frond, cylindrical to narrowly campanulate with lips usually parallel and with brown margins; receptacle usually covered by the lips.

Global distribution—Endemic to the Mascarenes.

Current distribution in Mascarenes— La Réunion, Mauritius.

Ecology—Epiphytic on tree-trunks or lithophytic on shaded, wet rocks in lowland rainforests, with a few populations on shaded, wet rocks in wet ravines of the western side of La Réunion in remnants of semi-dry forests (50–700 m).

Specimens examined— MAURITIUS. Valley Cascade, March 1975, D. Lorence 1174 ( MAU) ; Vallée d’Osterlog , October 2010, S. Hennequin et al. 367 ( MAU, P02432431 ) .

— LA RÉUNION. Brûlé de Takamaka, October 2010, S. Hennequin et al. 308 (P02432361).

Note—This species was initially considered endemic to Mauritius ( Roux 2009), but has recently been confirmed on La Réunion ( Grangaud 2010). But because of its minute size and possible confusion in the field with similar Didymoglossum species, its potential presence outside Mascarenes, and especially in Madagascar, awaits confirmation. Its distinction is nevertheless easy, because it is the only Didymoglossum species in the western Indian Ocean that does not display false veins parallel to true veins.

Figures

FIGURE 12. A. Didymoglossum barklyanum (Baker) J.P.Roux, as lithophyte (Mauritius, ‘Vallée d’Osterlog’). B. D. lorencei (Tardieu) Ebihara & Dubuisson, as lithophyte (La Réunion, ‘Grand Etang’). C. D. lorencei, detail of frond with marginal trichomes (photographs. A–C: J.-Y. Dubuisson; D: J.-M. Tamon).