Taxonomic and Nomenclatural Notes on Philippine Ferns. VI. Asplenium lepturus and A. contiguum (Polypodiales, Aspleniaceae), One or Two Species?

The present study clarifies the existing confusion between the Southeast Asian–Malesian Asplenium lepturus and the Hawaiian A. contiguum. The geographical range of both species is reported. Eleven (11) European and North American herbaria were visited by the author, and virtual collections of eight more herbaria were consulted. A morphological comparison of the size, shape, color, and dissection of the rhizome, scales, fronds, pinnae, apical segment, and sori was studied using light and dissecting microscopes. A. lepturus and A. contiguum are different species that can be distinguished by the size of the frond of fully developed plants, their different scales, the dentation of the pinna margin, the shape and length of the pinna apex, and sori position. A. lepturus is reported as a new Hawaiian species different from A. contiguum. A. lepturus is found in the Hawaiian Archipelago, south China, Laos, Vietnam, Philippines, and Sulawesi. A. contiguum is endemic in the Hawaiian Archipelago.