(2725) Proposal to conserve the name Polypodium rigidulum (Drynaria rigidula) against P. simplex (Polypodiaceae)

Abstract

(2725) Polypodium rigidulum Sw. in J. Bot. (Schrader) 1800(2): 26. Oct–Dec 1801, nom. cons. prop. Typus: [Indonesia], Java, Thunberg (UPS No. 24565). (=) Polypodium simplex Burm. f., Fl. Indica: 235. 1 Mar–6 Apr 1768, nom. rej. prop. Lectotypus (vide Mazumdar & al. in Candollea 74: 104. 2019): Indonesia, Pryon (G-PREL barcode G00818253). Polypodium rigidulum Sw. (l.c.), currently called Drynaria rigidula (Sw.) Bedd. (Ferns Brit. India: 314. 1869), is the only species of Drynaria with pinnate fronds and is widely distributed in China, Malaysia, Myanmar, Thailand, Vietnam; tropical Australia, and some Pacific islands (Polynesia) (Zhang & Gilbert in Wu & al., Fl. China 2–3: 766. 2013). The rhizome of Drynaria rigidula has been used in traditional medicine in Indonesia as an anti-infective agent (Nugraha & al. in Nat. Prod. Commun. 8: 703. 2013). In the protologue of Polypodium rigidulum, Swartz (l.c.) did not mention any collector's name or locality. However, Roos (in Verh. Kon. Ned. Akad. Wetensch., Afd. Natuurk., Sect. 2, 85: 234. 1986) cited the type as follows: “Type: Thunberg, Java (holo: S; iso: UPS, n.v.)”. Hovenkamp & Roos (in Fl. Malesiana, ser. 2, Ferns Fern Allies 3: 42. 1998) repeated Roos's (l.c.) citation of the S specimen: “Type: Thunberg (S), Java”, omitting the UPS specimen, which they had apparently not seen. A specimen in S (S-P-11482: http://herbarium.nrm.se/img/fbo/large/S-P-011001/S-P-11482.jpg), annotated only Drynaria rigidula by Roos in 1985, bears the red herbarium label “Isotypus”, but the original label has “Polypodium diversifolium Brown, non Willd., prodr. 147. East coast of New Holland, within the tropics. 1802. R. Brown scripsit et misit. Herb. Swartz”. Because it has no association with Thunberg or Java and was collected after P. rigidulum was published, it cannot be the cited “holo[type]”, and is presumably the isotype indicated by Roos (l.c: 235) for P. diversifolium in his synonymy under D. rigidula. Whether a holotype under ICN Art. 9.1 (Turland & al. in Regnum Veg. 159. 2018) or a lectotype under Art. 9.10, the type of P. rigidulum in S cited by Roos (l.c.) appears to be missing, as despite the assistance of curatorial staff, Lindsay & al. (in Gard. Bull. Singapore 69: 153. 2017) were unable to locate it. They therefore designated a UPS specimen (Cat. No. 24565) as lectotype. Lindsay & al.'s (l.c.) lectotypification is acceptable under Art. 9.11. Drynaria rigidula (basket fern) is a popular garden plant (Hoshizaki & Moran in Fern Grower's Manual: 295. 2001; Wiersema & León in World Econ. Pl., ed. 2: 257. 2013), and this name has been well known for a long time as evident by many citations in the literature (for example, Beddome, l.c. 1869, Suppl. Ferns S. Ind.: 24. 1876, Handb. Ferns Brit. India: 344. 1883; Copeland, Polypod. Phil. Isl.: 135. 1905, Gen. Fil.: 204. 1947, Fern Fl. Philipp.: 497. 1960; Alderwerelt, Malayan Ferns: 699. 1909, Malayan Ferns Fern Allies: 415. 1917; Backer & Posthumus, Varenfl. Java: 233. 1939; Tardieu & Christensen in Lecomte, Fl. Indo-Chine 7(2): 421. 1941; Holttum, Revis. Fl. Malaya 2: 183. 1954, in Dansk Bot. Ark. 20: 20. 1961, 23: 231. 1965; Tagawa in J. Jap. Bot. 38: 330. 1963; Roos, l.c.; Tagawa & Iwatsuki in Fl. Thailand 3: 550. 1989; Hovenkamp & Roos, l.c.; Bostock & Spokes in Fl. Australia 48: 475. 1998; Boonkerd & Pollawatn, Pterid. Thailand: 250, 270. 2000; Newman & al., Checkl. Vasc. Pl. Lao PDR: 30. 2007; Zhang & Gilbert, l.c.; Mazumdar & al. in Candollea 74: 104. 2019). However, Mazumdar & al. (l.c.: 104, fig. 7) recently found that the type specimen of Polypodium simplex Burm. f. (Fl. Indica: 235. 1768) at G-PREL (barcode G00818253) is actually Drynaria rigidula. Due to the priority of N.L. Burman's name, a combination in Drynaria based on P. simplex should replace D. rigidula, but that would be disruptive and disadvantageous to the nomenclature of this widely distributed and well-known species. So I propose here to conserve the name P. rigidulum against P. simplex to maintain nomenclatural stability of the former. JM, https://orcid.org/0000-0001-6127-2737 I sincerely thank Dr. J. Wiersema (US) and Prof. J. McNeill (E) for editing and improving the proposal.