New insights into the systematics and evolution of the filmy fern genus Crepidomanes (Hymenophyllaceae) in the Mascarene Archipelago with a focus on dwarf species

Abstract The diversity of species belonging to the filmy fern genus Crepidomanes (Hymenophyllaceae) in the Mascarene archipelago was studied, based on morphological investigations and focusing especially on the most dwarf species that are easily confused in the field and in herbarium collections. Morphological potential clusters and discriminations were then compared with an rbcL phylogeny. As a result, we recognized at least eight morpho-species for the archipelago and defined characters for distinguishing the three smallest ones, Crepidomanes bonapartei, Crepidomanes minutum and Crepidomanes (Trichomanes) trinerve. Morphological evidence and molecules confirm the specific status for T. trinerve (newly combined in Crepidomanes), the inclusion of Crepidomanes mannii into a C. minutum complex, and new records of C. bonapartei for Mauritius. The neotropical Polyphlebium pyxidiferum is found to be closely related to Afro-Madagascan Crepidomanes inopinatum and Crepidomanes melanotrichum species and so is newly combined in Crepidomanes. A key for the eight species of the genus in the archipelago, description of a new section clustering Crepidomanes frappieri and Crepidomanes longilabiatum, and new enhanced descriptions for two dwarf taxa (C. bonapartei and C. trinerve) are provided, and biogeographical origins of the genus in the Western Indian Ocean area are discussed.