A nomenclator for Elaphoglossum section Polytrichia (Dryopteridaceae), with notes on the identification and biogeography of its species

Elaphoglossum section Polytrichia is one of the main clades of the fern genus Elaphoglossum. It is usually distinguished from the rest of the genus by the presence of subulate scales and lack of hydathodes. Here we provide a nomenclatural synopsis with notes on the species taxonomy and identification, along with comments on the clade's biogeography. A total of 80 names were found to apply to species in the Polytrichia clade. Based on an examination of 3475 herbarium gatherings, we recognize in the group 53 species and two hybrids. The clade is almost entirely Neotropical, occurring from Mexico and the Antilles to Argentina and Brazil. The only exception is E. hybridum, which is widespread in South America but also occurs in Africa, Madagascar, and islands of the mid-Atlantic and Indian Oceans. We provide maps of geographic distribution and species richness for the section. Each species is provided with place and date of publication, information on types, complete synonymy, notes on geographic distribution, and other pertinent remarks. The following nomenclatural combinations are made: E. versatile and E. occidentale, comb. nov. Also, one epitype is designated for E. clathratum, lectotypes are designated for 13 names (Acrostichum barbatum, A. hybridum var. minor, A. mexicanum, A. nitidum, A. stramineum, E. angustioblongum, E. cinctum, E. cordifolium, E. demissum, E. erinaceum var. boliviense, E. lindbergii var. truncatum, E. reductum, E. truncatum), and neotypes are designated for E. hystrix and E. versatile. A list of the specimens examined is provided.