(3130) Proposal to conserve the name Araiostegiella faberiana ( Araiostegia faberiana , Davallia clarkei var. faberiana ) ( Davalliaceae ) with a conserved type and associated lectotypification of Araiostegiella perdurans ( Araiostegia perdurans , D. perdurans )

(3130) Araiostegiella faberiana (C. Chr.) M. Kato & Tsutsumi in Acta Phytotax. Geobot. 59: 12. 25 Mar 2008 ≡ Davallia clarkei var. faberiana C. Chr. in Acta Horti Gothob. 1: 73. 1924, nom. cons. prop. Typus: [China, Yunnan,] “N.W. of Tengyueh” [Tengchong], Jun 1925, Forrest 26764 (PE barcode 00050249), typ. cons. prop. In the fern family Davalliaceae, Araiostegia perdurans (Christ) Copel. (in Univ. Calif. Publ. Bot. 12: 397. 1931; based on Davallia perdurans Christ in Bull. Herb. Boissier 6: 970. 1898) and Araiostegia faberiana (C. Chr.) Ching (in Ching, Fl. Reipubl. Popul. Sin. 2: 293. 1959; based on Davallia clarkei var. faberiana C. Chr. in Acta Horti Gothob. 1: 73. 1924) have been documented as two morphologically similar but distinct species for over six decades (Ching, l.c.: 293–294; Wu in Wu, Fl. Reipubl. Popul. Sin. 6(1): 174–175. 1999; Xing & al. in Wu & al., Fl. China 2–3: 752. 2013). Both species share finely dissected laminae with sessile pinnae. Their main diagnostic distinction lies in that the basal pinnules of middle and lower pinnae are apparently catadromous (as explained below) in A. faberiana but opposite in A. perdurans. The genus Araiostegia Copel., nom. cons. (in Philipp. J. Sci. 34: 240. 1927) was indicated to be paraphyletic in a molecular phylogenetic study by Tsutsumi & al. (in Syst. Bot. 33: 44–48. 2008), in which the type species of Araiostegia together with some species of Davallodes Copel. (in Philipp. J. Sci., C 3: 33. 1908) were resolved in a clade, whereas samples of A. perdurans, A. faberiana, and A. parvipinnula (Hayata) Copel. (l.c. 1927: 241; based on Davallia parvipinnula Hayata in J. Coll. Sci. Imp. Univ. Tokyo 30: 431. 1911) were in a different clade. Consequently, Tsutsumi and Kato (in Acta Phytotax. Geobot. 59: 1–14. 2008) transferred most species traditionally placed in Araiostegia into Davallodes and established a new genus, Araiostegiella M. Kato & Tsutsumi, to accommodate Araiostegia perdurans and A. faberiana (treating A. parvipinnula as a synonym of A. perdurans). However, Fraser-Jenkins & al. (Annot. Checkl. Indian Pteridoph. 3: 57. 2021) argued that the catadromous lowest pinnules in Araiostegiella faberiana was “a variable feature of little taxonomic value” and considered it conspecific with A. perdurans, synonymizing the former under the latter. Upon examining the type specimens of the two names, we discovered an unexpected morphological discrepancy: the syntypes (A. Henry 10086 [NY barcodes 00128309 & 00128310; US No. 457575 = barcode 01100898 & No. 457576 = barcode 00065533], 10086A [E barcode E00417627; MO No. 1865430 = barcode MO-255776], and 10086B [P barcode P00643847]) of Araiostegiella perdurans comprise two morphologically distinct entities (one with opposite basal pinnules and another with catadromous pinnules), while the type specimens (E. Faber 1089 at K [barcode K000061879] and E [barcode E00348988]) of A. faberiana exclusively exhibit opposite pinnules. Notably, the morphology of type material of A. faberiana (Faber 1089) complies with the description of Araiostegia perdurans provided by Ching (l.c.) and subsequent authors for floras of China (e.g., Ching & Wu in Wu, Fl. Xizang 1: 286. 1983; Wu, l.c.; Xing & al., l.c.; Cheng in Wu, Fl. Yunnan. 21: 257. 2004), contradicting the diagnostic feature historically attributed to Araiostegia faberiana. To further assess the relationship and genetic differences between opposite-pinnuled material of Araiostegiella perdurans and catadromous-pinnuled material treated as A. faberiana, we performed novel molecular analyses on the plastid atpB-rbcL-accD fragment using the protocols described by Tsutsumi & al. (in Taxon 65: 1236–1248. 2016). Our sampling included eight Araiostegiella specimens: two A. faberiana (including a newly collected specimen from Yunnan, China), five A. perdurans (with one fresh Yunnan collection), and one A. hookeri (Bedd.) X.C. Zhang. Our analysis resolved these specimens into three strongly supported clades, each exhibiting substantial divergence (Dong & Huang, submitted to Phytotaxa in 2025). The A. perdurans clade formed a sister relationship with the A. hookeri clade, which collectively comprised a sister clade to the A. faberiana clade. Combined with our morphological observations from field surveys and herbarium examinations, these results convinced us that the opposite-pinnuled A. perdurans and catadromous-pinnuled A. faberiana represent distinct species. Given that the syntypes of Araiostegiella perdurans comprise morphologically heterogeneous elements, we hereby designate one of the syntypes, Henry 10086B at P (barcode P00643847), as the lectotype for Araiostegiella perdurans (Copel.) M.Kato & Tsutsumi to stabilize the application of the name A. perdurans for plants exhibiting opposite basal pinnules on all pinnae. Accordingly, to preserve nomenclatural continuity of the well-established epithet faberiana (under the genus Araiostegia, Araiostegiella, or Davallia), we formally propose the conservation of Araiostegiella faberiana with a conserved type under ICN Art. 14.9 (Turland & al. in Regnum Veg. 162. 2025). Specifically, we propose the well-preserved and complete specimen at PE, Forrest 26764 (barcode 00050249), as the conserved type of A. faberiana. This specimen bears Ching's original identification label dated 29 January 1959 (“Araiostegia faberiana”) and is annotated as “TYPUS” for the species’ description in Flora Reipublicae Popularis Sinicae. It unequivocally exhibits the diagnostic character of Araiostegiella faberiana: the basal pinnules of middle and lower pinnae are catadromous (the first pinnule arises on the basiscopic side of costa, extending from the costa-rachis joint, with the acroscopic pinnule's base being 6–10 mm distant from the rachis). An alternative approach to reconcile the conflict between the nomenclatural type and the current usage of the name Araiostegiella faberiana would be to subsume A. faberiana (including all homotypic synonyms) under A. perdurans, as proposed by Fraser-Jenkins & al. (l.c.), thereby necessitating the erection of a novel taxon for the plants with catadromous pinnules. However, conserving Araiostegiella faberiana with a conserved type is preferable for nomenclatural stability, because the epithet faberiana under Araiostegia has been accepted and widely used (e.g., Ching & Wu, l.c.; Wu, l.c.; Wang & al., l.c.; Cheng, l.c.; Tsutsumi & Kato, l.c.) since 1959 when it first appeared in Flora Reipublicae Popularis Sinicae (Ching, l.c.). We thank Chen Ren for his discussion on this proposal. This study was supported by Guangdong S&T Program (grant no. 2022B1111230001) and Bio-taxonomist Program of Chinese Academy of Sciences (CAS-TAX-24 047).