Molecular phylogenetic and morphological affinities of Adiantum senae (Pteridaceae)

Adiantum senae, a diminutive fern nearly restricted to southern Brazil, was described by Baker in 1885. In subsequent Floras, it was either completely overlooked or simply retained in the maidenhair genus Adiantum. However, a molecular phylogenetic analysis and a thorough morphological evaluation clearly demonstrate that this species does not belong in this genus. We find strong molecular support for the inclusion of A. senae within the cheilanthoid genus Adiantopsis, as a rather isolated lineage resolved as sister to the large, generally echinate-spored Glade. The position of sporangia in A. senae-along the vein tips of the main laminar tissue rather than on the abaxial tissue of the pseudoindusia-confirms the separation of this species from Adiantum, and the presence of arachnoid-echinulate spores reinforces its resolved position within Adiantopsis. Based on the sum of this evidence, we here provide a new combination, Adiantopsis senae (Baker) Schuettp. & A.Davila. Additionally, we designate a lectotype for A. senae, as well as for a later synonym.