Colloquia

         Neotropical Pteridology: A Dedication to Robbin Moran

Taxonomic revision of the Petiolatum Clade (Elaphoglossum, Dryopteridaceae)

Presenting Author
Ana Martinez
Description
Taxonomic revisions are the basis for understanding the Earth’s diversity. Elaphoglossum is a fern genus with a high diversity with ca. 600 species distributed in the tropics of the world. Molecular phylogenetic studies have contributed to advancing the understanding of Elaphoglossum in the last few years because they have promoted monographic work on small monophyletic groups. Here we present the taxonomic revision of one of those clades, the Petiolatum Clade. This group includes eight species distributed from Mexico to Panama and the Greater Antilles. Species in this clade are characterized by resinous dots on the abaxial surface of the lamina, rhizome scales with filiform to tortuouse apex and margins darker than the rest of the scale body, and spiny perispores. Taxonomic delimitation of the species belonging to the Petiolatum Clade has been challenging due to the lack of detailed taxonomic keys and descriptions. Especially, the taxonomy of the namesake species of this group, E. petiolatum, has been complicated because of its great variation and wide distribution. For the taxonomic revision, we consulted the protologues and type specimens of the eight species belonging to the clade and their synonyms and studied more than 2000 herbarium specimens, as well as spore micromorphology using scanning electron microscope images. The morphological characters that help to distinguish species within the clade are the shape, size, and color of the rhizome and the laminar scales, the presence and type of resinous dots on the abaxial surface of the lamina, and the perispore ornamentation. Based on our studies we provide an identification key and detailed descriptions that include images of the plants and their most characteristic morphological structures, distribution maps, and nomenclatural, ecological, phenological, and taxonomic notes for each of the eight species. We made a new nomenclatural combination, designated four lectotypes, described a new species endemic to Guatemala, and recognized two species that had been placed under synonymy.