A taxonomic and biogeographic reappraisal of the genus Dicksonia (Dicksoniaceae) in the Neotropics

Abstract

We evaluate morphological characters of South AmericanDicksonia(Dicksoniaceae) gathered from field observations and herbarium specimens. We here adopt the taxonomic concept of earlier authors and separateD. sellowianaof southeastern Brazil fromD. navarrensis(=D. giganteaauct.) andD. karsteniana,which occurmainly in Mesoamerica and in the Andes, respectively. The latter species is especially variable in plant size and persistence of the hairy indument, which can be correlated with local ecological conditions. For plants with small, hairy fronds from shrubby páramo vegetation, we here propose to reinstate a varietal name,D. karstenianavar.arachnoidea, and for glabrescent plants regularly found at lower elevations in closed forest we suggestD. karstenianavar.spruceana. Dicksonia stuebeliiis maintained as a separate species and is reported from northern Colombia for the first time. One species is recognized as new,D. lehnertiana; it is characterized by relatively small, long-stalked fronds with spreading bristly hairs. Results of an S-DIVA biogeographical analysis implemented on an updated phylogeny of NeotropicalDicksoniaseparateD. sellowianain southeastern Brazil clearly from the rest of the taxa, whose ancestral area is reconstructed as northern Andes–southern Mesoamerica. However, the resolution and support in this group could be improved. Our results have significance for conservation efforts, asD. sellowianais now virtually a Brazilian endemic.