J Syst Evol

• Research Article •    

Diversity, taxonomy, and history of the tropical fern genus Didymoglossum Desv. (Hymenophyllaceae, Polypodiidae) in Africa

Jean‐Yves Dubuisson1*, Adèle Nivart1, Ehoarn Bidault2,3, Vincent Deblauwe4,5,6, Vincent Droissart4,7,8, Narcisse G. Kamdem8, Germinal Rouhan3, Atsushi Ebihara9, and Timothée le Péchon10,11   

  1. 1 Institut de Systématique, Evolution, Biodiversité (ISYEB), Sorbonne Université, MNHN, CNRS, EPHE, Université des Antilles, CP 48, 57 rue Cuvier 75005 Paris, France
    2 Missouri Botanical Garden, Africa & Madagascar Department, 4344 Shaw Boulevard, Saint Louis, MO 63110, USA
    3 Institut de Systématique, Evolution, Biodiversité (ISYEB), Muséum national d'Histoire naturelle, CNRS, SU, EPHE, Université des Antilles, CP 39, 57 rue Cuvier, 75005 Paris, France
    4 Herbarium et Bibliothèque de Botanique africaine, CP 265, Université Libre de Bruxelles, Boulevard du Triomphe, B‐1050 Brussels, Belgium
    5 International Institute of Tropical Agriculture (IITA), BP 2008 (Messa), Yaoundé, Cameroon
    6 Center for Tropical Research, Institute of the Environment and Sustainability, University of California Los Angeles, Los Angeles, CA 90095, USA
    7 AMAP Lab, Univ. Montpellier, IRD, CNRS, INRAE, CIRAD, Montpellier, France
    8 Plant Systematics and Ecology Laboratory, Higher Teachers' Training College, University of Yaoundé I, Yaoundé, Cameroon
    9 Department of Botany, National Museum of Nature and Science, 4‐1‐1 Amakubo, Tsukuba 305‐0005, Japan
    10 Meise Botanic Garden, Nieuwelaan 38 1860 Meise, Belgium
    11 Fédération Wallonie‐Bruxelles, Service Général de l'Enseignement supérieur et de la Recherche scientifique, 1 rue A. Lavallée 1080 Bruxelles, Belgium
    *Author for correspondence. E‐mail: dubuisson@mnhn.fr
  • Received:2022-11-18 Accepted:2023-01-31 Online:2023-03-28

Abstract: The fern genus Didymoglossum (Hymenophyllaceae) is not so diverse in Africa with seven species at most. However, its local taxonomy is surprisingly still strongly debated, in particular within the Didymoglossum erosum complex interpreted either as a single polymorphic species or as a group of at least three distinct but morphologically very close taxa (D. erosum, Didymoglossum chamaedrys, and Didymoglossum benlii). Investigating these taxonomic issues and more generally the diversity of the genus in Africa and its origin, we conducted a complete anatomo–morphological analysis coupled with a molecular phylogenetic work based on rbcL. Our results support the recognition of all seven species, including Didymoglossum robinsonii that is likely distinct from the Neotropical Didymoglossum reptans to which the African populations were traditionally attributed. We here propose new characters and a novel key to distinguish the seven African species which also include Didymoglossum ballardianum, Didymoglossum lenormandii, and Didymoglossum liberiense. Once the taxonomy is clarified with respect to the distinct evolutionary lineages evidenced, the biogeographic history of the genus in Africa is discussed based on a divergence time estimation and the reconstruction of the ancestral geographic areas. These analyses reveal a Mesozoic (Cretaceous) vicariance event within Didymoglossum which is the second one hypothesized for the family Hymenophyllaceae.

Key words: biogeography, filmy ferns, vicariance, western Indian Ocean