Didymoglossum robinsonii (Hook. ex Baker) Copel.

Ahamada H. Saïd, Sabine Hennequin, Germinal Rouhan & Jean-Yves Dubuisson, 2017, Disentangling the diversity and taxonomy of Hymenophyllaceae (Hymenophyllales, Polypodiidae) in the Comoros, European Journal of Taxonomy 313, pp. 1-53 : 15-16

Didymoglossum robinsonii (Hook. ex Baker) Copel.

Didymoglossum robinsonii (Hook. ex Baker) Copel., The Philippine Journal of Science 67: 77, t. 31, figs 7, 8 (1938). – Trichomanes robinsonii Hook. ex Baker , Journal of the Linnean Society, Botany 9: 339, t. 8B (1866), as ‘ robinsoni ’. – Type: Natal, E.A. Robinson s.n. (syn-: K000435669!, K000435670!); Natal, J. Sanderson s.n. (syn-: K000435671!).

Trichomanes reptans Sw. var. major Mett. ex Kuhn, Filices Africanae : 37 (1868). – Type: ‘Natalia’, s. loc., s.d., s. coll. s.n. (Herb. Hooker).

Short description

Epiphytic; long-creeping filiform rhizomes, rootless and densely covered by dense black trichomes, bearing widely separated pending fronds; fronds subsessile or with short stipes, up to 5 cm long, oblong to ovate, lobed to pinnatifid, with palmate to pinnate venation and false veins parallel to true veins, hairy with dark not pedunculated trichomes on lamina margins; sori few, epitactic, cylindrical with lips usually parallel and with brown margins.

Global distribution

Comoros, Madagascar, Tanzania, South Africa.

Distribution in Comoros

Anjouan.

Additional specimen examined

COMOROS: ANJOUAN, les forêts des sommets les plus élevées, May 1850, L.H. Boivin s.n. (P02439524).

Note

African Didymoglossum robinsonii is morphologically quite close to D. reptans (Sw.) C.Presl and as such was considered a synonym of the latter species ( Wessels Boer 1962; Roux 2009). In addition, paleotropical D. reptans has often been identified as D. montanum (Hook.) J.P.Roux , especially by Sim (1915) or Tardieu-Blot (1951). Types of D. reptans and D. montanum are both neotropical, and exhibit identical diagnostic characters, explaining why we consider that these two taxa are synonyms ( D. reptans has priority) as previously considered by Wessels Boer (1962). By considering such synonymy and the a priori of paleotropical D. reptans populations, D. reptans would be present in Neotropics, in eastern and southern Africa and in the western Indian Ocean, but would be absent in western and central Africa (according to collections and Roux 2009). However, unpublished personal molecular data (based on rbc L sequences) would indicate that neotropical D. reptans would be genetically close and yet distinct from paleotropical specimens from Madagascar and Comoros (i.e., they do not form a monophyletic cluster). The disjunct distribution and the genetic differences thus suggest that Comorian supposed D. reptans (often identified as D. montanum ) could be a distinct species and thus likely considered D. robinsonii (type from South Africa) as a distinct (potentially cryptic) taxon and not a synonym of D. reptans . Additional molecular phylogenetic investigations including African specimens are required to clarify the taxonomic status of the paleotropical populations. Pending such revision we name the Comorian species D. robinsonii .