(3047) Proposal to conserve the name Ctenitis against Atalopteris (Dryopteridaceae)

(3047) Ctenitis (C. Chr.) C. Chr. in Verdoorn, Man. Pteridol.: 544. 3 Apr 1938 (Dryopteris subg. Ctenitis C. Chr. in Rosenvinge, Biol. Arbejder Tilegnede Eug. Warming: 77. 3 Nov 1911), nom. cons. prop. Typus: Dryopteris ctenitis (Link) Kuntze) (Aspidium ctenitis Link). (=) Atalopteris Maxon & C. Chr. in Contr. U. S. Natl. Herb. 24: 55. 15 Aug 1922, nom. rej. prop. Typus: A. aspidioides (Griseb.) Maxon & C. Chr. (Polybotrya aspidioides Griseb.). Ctenitis (C. Chr.) C. Chr. (in Verdoorn, Man. Pteridol.: 544. 1938a) is a pantropical genus of the fern family Dryopteridaceae with 125 species presently recognized (PPG I in J. Syst. Evol. 54: 563–603. 2016). This genus name has been widely and consistently used in regional floristic works (e.g., Proctor, Ferns Jamaica: 416–425. 1985; Moran in Davidse & al., Fl. Mesoamer. 1: 196–200. 1995; Mickel & Smith, Pterid. Mexico: 219–233. 2004; Dong & Christenhusz in Wu & al., Fl. China 2–3: 558–561. 2013; Duan & al. in Ann. Missouri Bot. Gard. 102: 3–86. 2017; Viveros & al. in Phytotaxa 385: 1–83. 2017). Ctenitis was first published by Christensen (in Rosenvinge, Biol. Arbejder Tilegnede Eug. Warming: 77. 1911) as the epithet of a subgenus of Dryopteris and remained so for the next 27 years. Although Christensen (in Kongel. Danske Vidensk. Selsk. Skr., Naturvidensk. Math. Afd., ser. 7, 10: 84. 1913a) already considered the particular pubescence of Ctenitis (ctenitoid hairs) to be of sufficient taxonomic value to recognize it as a genus distinct from Dryopteris, it was not until 1938 that Ctenitis was treated as such. In 1938, the name Ctenitis was changed to the rank of genus by Christensen on two occasions: the first time in the Manual of Pteridology, published in April (Christensen, l.c. 1938a), and the second time in October, in "Les fougères d'Indochine. XIV Dryopterideae" (Tardieu-Blot & Christensen in Notul. Syst. (Paris) 7: 86. 1938). In publishing Ctenitis in the Manual of Pteridology (Christensen, l.c. 1938a), Christensen indirectly referred to the basionym Dryopteris subg. Ctenitis through the phrase "(Dryopteris part. auctt.)". Additionally, Christensen (l.c. 1938a: 525–526) cited in the bibliographic list: (1) "Index Filicum" (Christensen, Index Filic. Suppl. 1: 19. 1913b), and (2) "Monograph of the genus Dryopteris, Part I, the Tropical American pinnatifid-bipinnatifid species" (Christensen, l.c. 1913a: 82). In both these publications the basionym, Dryopteris subg. Ctenitis, is fully and directly referenced. We are of the opinion that, in this case, Art. 41.3 of the Shenzhen Code (Turland & al. in Regnum Veg. 159. 2018), which states that an indirect reference to a basionym is sufficient for valid publication of a name at new rank, is complied with. Although Christensen (l.c. 1938a) provided a description of Ctenitis, it was in English and not Latin as required in 1938 and so, unless the indirect reference to the subgeneric name is accepted, Ctenitis would not be validly published there and so Art 41.4 is not applicable. However, should the General Committee consider that the indirect reference to the basionym Dryopteris subg. Ctenitis through the phrase "(Dryopteris part. auctt.)" in the Manual of Pteridology (Christensen, l.c. 1938a: 544) is insufficient to consider it as the valid publication of the name Ctenitis, the conservation of this name should be based on the later publication (Christensen, l.c. 1938b: 86). In this case, a full and direct reference to the author and place of valid publication is given for the basionym, Dryopteris subg. Ctenitis. Ching (in Bull. Fan Mem. Inst. Biol. Bot. 8: 275, 277. 1938) designated Aspidium ctenitis Link as the type of the generic name Ctenitis, but also noted that the correct name for the species in Ctenitis is C. distans (Brack.) Ching (Lastrea distans Brack.). Aspidium ctenitis and Ctenitis distans are heterotypic synonyms, a synonymy apparently first noted by Christensen (l.c. 1913a: 93). Link (Hort. Berol. 2: 122. 1833) did not designate a type for Aspidium ctenitis, but Christensen (l.c. 1913a: 93) mentioned that Link based this name on a plant cultivated in the Botanical Garden in Berlin, with specimens in B, but indicated that the species was native to Brazil. Later, Viveros & al. (l.c.: 40) designated the specimen with barcode B 20 0054401 as the lectotype of A. ctenitis. Lastrea distans is also from Brazil being based on a specimen collected in the Organ Mountains, Rio de Janeiro, in 1838–1842, during the South Pacific Exploring Expedition commanded by Capt. Wilkes (US No. 50547 [barcode 00067060]). The fact that Ching (l.c. 1938: 277) mentioned that "distans" is the earliest epithet for this taxon available in Ctenitis immediately after designating Aspidium ctenitis Link as the type for the generic name has generated confusion resulting in a wide acceptance of C. distans (Brack.) Ching as the type for Ctenitis (e.g., Tryon & Tryon, Ferns Allied Pl.: 468–470. 1982; Proctor, l.c.; Tryon & Stolze in Fieldiana, Bot., n.s., 27: 5–11. 1991; Mickel & Smith, l.c.; PPG I, l.c.; Viveros & al., l.c.). However, the correct type for Ctenitis is the type of Aspidium ctenitis Link (Ching, l.c. 1938: 275, 277). The type of C. distans is not eligible, even though the basionym to which it applies is a synonym of Aspidium ctenitis Link and provides the earliest epithet for that species in Ctenitis, because Christensen (l.c. 1911) did not include it in Dryopteris subg. Ctenitis. The Index Nominum Genericorum (ING) refers to another attempt to designate the type of Ctenitis, this by C. submarginalis (Langsd. & Fisch.) Ching (Polypodium submarginale Langsd. & Fisch.) by Ching (in Sunyatsenia 5: 250. 1940). This attempt is posterior to the effective designation of Aspidium ctenitis as the type for Ctenitis (Ching, l.c. 1938: 275, 277) and is therefore also incorrect. Among the dryopteroid ferns, the genus Atalopteris Maxon & C.Chr. (in Contr. U. S. Natl. Herb. 24: 55. 1922) is endemic to the Greater Antilles (except Puerto Rico) and comprises three species. The genus was described to include two species: A. aspidioides (Griseb.) Maxon & C. Chr. (Polybotrya aspidioides Griseb.), the type from Cuba, and A. maxonii (Christ) C. Chr. (Psomiocarpa maxonii Christ), from Jamaica. Christensen (l.c 1913a) had already recognized the close morphological affinity of these Antillean species with Ctenitis species (treated as part of Dryopteris subg. Ctenitis in that monograph) in characters such as habit, texture and indument. However, he considered the extreme leaf dimorphism to be enough to place these species in a separate genus (Christensen, l.c. 1913a). Since its description, the name Atalopteris has been commonly used in fern lists and taxonomic treatments for the Greater Antilles (e.g., Christensen in Kongl. Svenska Vetensk. Akad. Handl., ser. 3, 16(2): 1–93. 1936; Duek in Adansonia, ser. 2, 11: 722. 1971; Tryon & Tryon, l.c.; Proctor, l.c.: 415–416; Sánchez in Brittonia 69: 489. 2017, in Revista Jard. Bot. Nac. Univ. Habana 42: 12. 2021). Only Kramer & al. (in Kubitzki, Fam. Gen. Vasc. Pl. 1: 126. 1990) have previously considered Atalopteris to be a synonym of Ctenitis. A recent molecular phylogenetic study by the authors of this proposal, using plastid DNA (Regalado & al., accepted), revealed that Atalopteris is phylogenetically nested within Ctenitis, a relationship that is strongly supported. Although the three species previously included in Atalopteris differ from most of Ctenitis taxa by having complete foliar dimorphism, the merger of the two genera is also supported by morphological characters such as the common presence of ctenitoid hairs, non-sulcate costae, persistent divaricate scales upon the rachis and the lower side of the costae, and the echinate perispore (Maxon in Contr. U. S. Natl. Herb. 24: 55. 1922; Regalado & al., accepted). The current proposal is made with the aim of maintaining nomenclatural stability. We therefore recommend that the name Ctenitis should be conserved over Atalopteris. This arrangement would prevent the disruption that would result from making more than a hundred new combinations if the name Ctenitis is not conserved against Atalopteris. We are grateful to John McNeill, Werner Greuter, and Rosa Rankin for their advice to solve nomenclatural and typification issues.