Crepidomanes inopinatum (Pic.Serm.) J.P.Roux var. tamonii Y. Robert & 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 : 20-21

8. Crepidomanes inopinatum (Pic.Serm.) J.P.Roux var. tamonii Y. Robert & Dubuisson ( Dubuisson et al. 2014: 165,

166), Fig. 10B

Type:— LA RÉUNION. La Possession, ravine de la Grande Chaloupe, August 2006, Y. Robert 913 (holotype P, P02433924 !; isotype REU!)

Short description—Similar to the typical variety but usually lithophytic with dwarf fronds up to 4 cm long and often when dry, folds parallel to veins.

Global distribution— La Réunion, one population reported in Mauritius.

Ecology—Lithophytic on wet and shaded rocks in wet ravines of the western side in semi-dry forest remnants, in addition to a few populations in locally-called ‘végétation de fond de cirque’ in north-eastern side (‘Rivière du Mât’ or ‘Mare à Poule d’eau’), at low elevations (150–900 m).

Specimens examined— MAURITIUS. Curepipe, Trou aux cerfs, October 2015, Pynee et al. s.n. (MAU 0017487, MAU 0017488).

— LA RÉUNION. Vallée de la Grande Chaloupe, La Montagne, October 1972, T. Cadet 3810 ( REU08464 ) ; Ravine des Avirons , August 2005, E. Grangaud 1688-1 ; Sentier du Petit Louis, Grand Bassin, June 2006, Y. Robert 885 ; Tampon, sentier Piton Petit Louis vers Grand-Bassin, June 2006, Y. Robert s.n .; Sainte Marie, ravine Kiwi, July 2006, Y. Robert 890 ; Bras Panon, berges de la rivière du Mât, July 2009, Y. Robert 1298 ; Salazie, mare à Poule d‘eau, August 2009, Y. Robert 1317 ; Saint Louis, les Canots, January 2014, Y. Robert 1655 ; Saint Leu, ravine du Trou, December 2005, Tamon & Fontaine s.n.; Sainte Marie, falaise du Cap Soldat, October 2007, Tamon s.n .; La Possession, Ilet Solitude, december 2007, Tamon s.n ; La Possession, Sentier de Dos d‘Ane vers Deux bras, March 2010, Tamon s.n. Note : Except T. Cadet 3810 available in REU, the holotype available at P and the Mauritian specimens, all other examined specimens are available in respective private collections of E. Grangaud , Y. Robert and J.- M. Tamon (La Réunion) .

Note—As Dubuisson et al. (2013, 2014) have shown, this dwarf variety can easily be confused with C. trinerve , found in equivalent lowland habitats, especially when specimens show laminar folds parallel to veins. Subtle differences concern the sori, which exhibit a slightly dilated mouth vs. a well dilated bilabiate mouth for C. trinerve (see Fig. 11B ), and laminar cells, which have straight walls vs. undulated wavy walls for C. trinerve (see Figs 2 and 3 in Dubuisson et al. 2013). A population was observed in Mauritius for the first time in 2015 (see above).

Figures

FIGURE 2. Wet Mascarenan ecosystems. A. Lowland windward rainforest dominated by Sapotaceae trees, showing the understory with numerous low epiphytic and terrestrial free-sporing plants (liverworts, mosses, ferns, lycopods and spikemosses) and a few herbaceous angiosperms (especially orchids) (La Réunion, ‘Mare Longue’ forest, ~450 m). B. Montane rainforest dominated by Dombeyoideae (Malvaceae) trees and Alsophila spp. tree-ferns (Cyatheaceae) as emergents from the canopy (La Réunion, ‘Cassé de Takamaka, Bébour’, 1,100–1,200 m). C. Montane ericoid thickets (La Réunion, ‘Enclos du Piton de la Fournaise’, ~2,200 m). (Photographs. A, C: C. Chaussidon; B: J.-M. Tamon).

FIGURE 3. Particular Mascarenan ecosystems. A. Hyperhumid montane ‘Avoune’ vegetation dominated by the endemic Erica reunionensis (Ericaceae), with most trunks and branches fully covered by epiphytes (liverworts, mosses, peat mosses, lycopods and ferns, especially here Hymenophyllum capillare and H. inaequale, and orchids) (La Réunion, ‘Pitons Mare à Boue’, ~1,600 m). B. Montane ‘Tamarinaie’ dominated by endemic Acacia heterophylla (Fabaceae), showing as for ‘Avoune’ tree-trunks and branches fully covered by epiphytes, including here H. inaequale (La Réunion, ‘Bélouve’, ~1,520 m). C. Remnant of leeward lowland semi-dry forest (La Réunion, ‘Ilet Solitude’, ~550 m). D. Typical wet ravines that host lithophytic Hymenophyllaceae on the wet and shaded rocks close to streams and waterfalls. (photographs.A: J.-Y. Dubuisson; B–C: J.-M. Tamon; D: A. Mercier).

FIGURE 10. A. Crepidomanes inopinatum (Pic.Serm.) J.P.Roux var. inopinatum, as lithophyte (La Réunion, ‘Petite Plaine’). B. C. inopinatum var. tamonii Y.Robert & Dubuisson, habit (Y. Robert 913, P02433924). C. C. minutum (Blume) K.Iwats. var. minutum, as epiphyte (La Réunion, ‘Bébour’). D. C. minutum var. minutum, frond with long terete wingless stipe. E. C. minutum var. minutum, showing stipe proliferation, scale = 1 cm (from Madagascar, F. Rakotondrainibe 3698, P00085267). F. C. minutum var. mascarenense Pynee & Dubuisson, as epiphyte (La Réunion, ‘Grand Etang’). G. C. minutum var. mascarenense, detail of fronds with short stipes. (photographs. A: J.-Y. Dubuisson; C–D: C. Chaussidon; F–G: E. Grangaud).

FIGURE 11. Crepidomanes trinerve (Baker) Dubuisson & Ebihara. A. As lithophyte in a wet ravine of the western side of La Réunion (‘Les Canots’; photograph by J.-M. Tamon). B. Habit (from Comores, F. Rakotondrainibe 6651, P00310478; modified from Dubuisson et al. 2013).