(3069) Proposal to conserve the name <i>Elaphoglossum metallicum</i> against <i>E. pachycraspedon</i> (<i>Dryopteridaceae</i>)

(3069) Elaphoglossum metallicum Mickel in Fieldiana, Bot., ser. 2, 27: 146. 28 Feb 1991, nom. cons. prop. Typus: Peru, San Martín, Zepelacio, near Moyobamba, Mai 1934, Klug 3636 (NY barcode 00149668; isotypi: F No. 753194, GH barcode 00021184, K barcode K000590652, MO No. 1088746 [barcode MO-255710], US No. 1458021 [barcode 00588554]). (=) Elaphoglossum pachycraspedon Christ in Hedwigia 44: 362. 25 Aug 1905, nom. rej. prop. Lectotypus (hic designatus): Peru, Loreto, Cerro de Escaler, Jan 1903, Ule 6890 (B barcode B 20 0071406). Elaphoglossum is the second-largest fern genus, comprising approximately 600 species distributed across tropical and subtropical regions worldwide (Matos & al. in Syst. Bot. 46: 764–789. 2021). Despite its diversity, only about 10 species are commonly cultivated for their ornamental appeal (Hoshizaki & Moran, Fern Grower's Man.: 320–325. 2001). Among these, E. metallicum Mickel stands out for its striking, iridescent, metallic-blue fronds, making it particularly attractive in horticulture. The publication of the name Elaphoglossum pachycraspedon Christ (in Hedwigia 44: 362. 1905) predates that of E. metallicum Mickel (in Fieldiana, Bot., ser. 2, 27: 146. 1991) and therefore has nomenclatural priority under the International Code of Nomenclature (ICN; Turland & al. in Regnum Veg. 159. 2018). Elaphoglossum pachycraspedon, however, has been rarely used in the literature. It has appeared in only three publications since its original description: Murillo-Pulido & Harker-Useche (Helechos Pl. Afines Colombia: 274. 1990), Murillo-Pulido & al. (Pteridóf. Colombia: 243. 2008), and Vasco (in Bernal & al., Cat. Pl. Líq. Colombia 1: 484. 2016), the last noting that earlier references were “based on a misidentification”. Despite having a type from Peru, the name was overlooked in Mickel's (l.c.) treatment of the genus for Pteridophyta of Peru. The original publication of Elaphoglossum pachycraspedon by Christ in 1905, shortly after his major monograph of the genus (Christ, Monogr. Elaphoglossum: 1–159. 1899), may have contributed to its oversight. Additionally, the type specimen's sole deposition in the Berlin Herbarium (B barcode B 20 0071406, designated as lectotype) has limited accessibility for verification and study. In contrast, Elaphoglossum metallicum has been widely cited and its types are distributed in many herbaria (F, GH, K, MO, NY, US). Geographically, E. metallicum has been documented in Colombia (Vasco, l.c.: 482; Idárraga-Piedrahita & al., Fl. Antioquia, Cat. 2: 161. 2011), Ecuador (Neill & Ulloa Ulloa, Ad. Fl. Ecuador, Segundo Supl., 2005–2010: 1–202. 2011), and Peru (Mickel, l.c.; Alva & al., Divers. Floríst. N. Perú 2: 258. 2003). Many records for these countries are to be found in databases such as GBIF (80 occurrences for E. metallicum vs. only 6 for E. pachycraspedon, as of 1 January 2025) and iNaturalist (3 observations vs. 0). The name E. metallicum has also appeared in a taxonomic study of E. sect. Elaphoglossum by Rojas-Alvarado (in Revista Biol. Trop. 51: 4. 2003), a study on perine evolution in Elaphoglossum by Moran & al. (in Int. J. Pl. Sci. 171: 872–881. 2010), a study on the role of structural adaptations in leaf iridescence by Strout & al. (in Ann. Bot. (Oxford) 112: 1141–1148. 2013), and several molecular phylogenetic studies focused on Elaphoglossum, such as Rouhan & al. (in Molec. Phylogen. Evol. 33: 745–763. 2004), Skog & al. (in Int. J. Pl. Sci. 165: 1063–1075. 2004), and Matos & al. (in Int. J. Pl. Sci. 179: 296–313. 2018). Notably, Elaphoglossum metallicum was highlighted by Hoshizaki & Moran (l.c.: 323) and León & al. (Ornamental Ferns Peru: 42. 2012) as one of the few species of Elaphoglossum in cultivation. In fact, it appears to be the most prominent representative of the genus in horticulture as evidenced by its presence on many international sales platforms. A search on Google using the keywords “Elaphoglossum metallicum for sale” yielded results from numerous vendors across Latin America, the United States, Europe and Asia. To maintain nomenclatural stability and preserve its prevailing scientific and horticultural use, the name Elaphoglossum metallicum is proposed here to be conserved over E. pachycraspedon. The widespread adoption of E. metallicum by the scientific and horticultural communities underscores the practical and academic usefulness of this proposal. This research was partially funded by the Reference Center for Environmental Information (CRIA, in Portuguese). I thank the curators of the herbaria mentioned above for images of their specimens. I also thank Dr. Robbin Moran for his constructive comments on the manuscript.