(2962) Proposal to conserve the name Ranunculus rionii against R. bauhini (Ranunculaceae)

(2962) Ranunculus rionii Lagger in Flora 31: 50. 28 Jan 1848 [Angiosp.: Ranuncul.], nom. cons. prop. Typus: Switzerland, “Ranunculus Rionii Lagger / Sion en Valais / Lagger. / communicavit Buchinger”, [C. Rion] (NCY barcode NCY023996). (=) Ranunculus bauhini Tausch in Flora 17: 525. 7 Sep 1834, nom. rej. prop. Lectotypus (hic designatus): “R[anunculus]. Bauhini Tau., Ex Europa austr.”, Sieber (PRC barcode PRC 456084). The name Ranunculus bauhini was proposed by Tausch (in Flora 17: 525. 1834) for a member of a group of aquatic species of Ranunculus, which is sometimes recognized as a separate genus Batrachium (e.g., Gray, Nat. Arr. Brit. Pl. 2: 720. 1821; Janchen, Cat. Fl. Austr. 1(2): 195. 1958; Wang & Tamura in Wu & al., Fl. China 6: 431. 2001; Eichler & Jeanes in Wilson, Fl. Austral. 2: 310. 2007), a subgenus (e.g., Seringe, Fl. Jard. 3: 48. 1849; Cook in Mitt. Bot. Staatssamml. München 6: 83. 1966; Cook in Tutin & al., Fl. Eur., ed. 2, 1: 285. 1993; Whittemore in FNA Ed. Comm., Fl. N. Amer. N. Mexico 3: 130. 1997) or a section of Ranunculus (e.g., Candolle, Syst. Nat. 1: 232. 1817; Emadzade & al. in Taxon 59: 819. 2010; Wiegleb & al. in Phytotaxa 319: 1. 2017). Tausch (l.c.) cited two elements in his protologue of Ranunculus bauhini: the pre-Linnaean polynomial “R[anunculus]. aquatilis omnino tenuifolius J. Bauh. hist. 3. p. 781. f. 2” and a collection with the provenance indicated as “Habitat in Europa australi, unde plura specimina attulit D. Sieber.” The illustration of “Ranunculus aquatilis omnino” in Bauhin's Historia plantarum universalis (3: 781. 1651) shows a homophyllous aquatic Ranunculus, which has only capillary leaves, small flowers and short peduncles, such as those that are now known under the names of R. trichophyllus Chaix (Pl. Vapinc.: 31. 1785) and R. rionii Lagger (in Flora 31: 49. 1848). The single illustrated aggregate fruit is of conical-ovoid shape, which indicates a receptacle elongating in fruit, a character typical of the species currently known as R. rionii. The authentic specimen collected by F.W. Sieber (probably in one of his collecting trips to Italy and Crete in 1812 and 1817, respectively) and cited by Tausch in the protologue was recently discovered in PRC. The plant has both flowers and fruits, which have small glabrous achenes and receptacles elongated to the conical shape. The plant is undoubtedly taxonomically identical to the species currently known as R. rionii. The description of R. bauhinii given by Tausch (l.c.) is consistent with R. rionii as well. To the best of our knowledge, the name Ranunculus bauhini has never been adopted apart from in its protologue. Soon after its original publication it was interpreted as a synonym of R. aquatilis by Steudel (Nomencl. Bot., ed. 2, 2: 432. 1841). This view was adopted in Index Kewensis (Jackson, Index Kew. 2: 683. 1895). Subsequently, the name R. bauhini almost completely disappeared from the literature. We failed to find it in the taxonomic studies dealing with aquatic Ranunculus as well as in consulted floras of central and southern Europe. This name is absent even from most of the taxonomic revisions and monographs of Ranunculus sect. Batrachium (e.g., Godron in Mém. Soc. Roy. Sci. Nancy 1839: 8–41. 1840; Wiegleb & al., l.c.). The only exception is the monograph by Cook (l.c. 1966: 129) where, however, R. bauhini is only listed among unclear names that “may refer to a terrestrial state of either R. trichophyllus, R. aquatilis or R. peltatus”. In any case, in spite of the extensive searching in the literature, we have not found a single instance where R. bauhini is recognized. If the name is incorporated in online databases, it is registered only as a synonym of R. aquatilis (Global Biodiversity Information Facility, https://www.gbif.org; Plants of the World Online, https://powo.science.kew.org; World Flora Online, http://www.worldfloraonline.org) or the status is not indicated (International Plant Names Index, https://www.ipni.org), while in many other databases the name is not given at all (including Euro+Med PlantBase, https://www.europlusmed.org, and Tropicos, http://tropicos.org; all databases accessed 5 Dec 2022). In contrast, Ranunculus rionii is a widely used name, consistently applied for the particular species since its original publication. It has been accepted in a wide range of publications that include the relevant national and regional floras and checklists (e.g., Damboldt in Hegi, Ill. Fl. Mitt.-Eur., ed. 2, 3(3): 315. 1974; Cook, l.c. 1993: 286; Dahlgren in Strid & Tan, Fl. Hellenica 2: 67. 1997; Tsvelev, Fl. Vost. Evr. 10: 174. 2001, sub Batrachium rionii; Wang & Tamura in Wu & al., l.c.: 433, sub B. rionii; Danihelka & al. in Preslia 84: 679. 2012, sub B. rionii), monographs and revisions (Cook, l.c. 1966: 141; Pizarro in Lazaroa 15: 43. 1995; Wiegleb & al., l.c.), other taxonomic and biosystematics studies (e.g., Dahlgren in Pl. Syst. Evol., Suppl. 9: 315. 1995; Bobrov & al. in Phytotaxa 233: 106. 2015; Englmaier in Neilreichia 8: 115. 2016; Prančl & al. in Preslia 90: 199. 2018; Koutecký & al. in Bot. J. Linn. Soc. 198: 419. 2022), distribution atlases (e.g., Jalas & Suominen, Atlas Fl. Europ. 8: 219. 1989; Kaplan & al. in Preslia 91: 341. 2019), floristic papers (e.g., Cook & Patzak in Österr. Bot. Z. 109: 372. 1962; Wolff in Bull. Soc. Bot. France 136: 235. 1989; Wolff & Schwarzer in Florist. Rundbr. 25: 69. 1991; Kaplan in Zprávy České Bot. Společn. 29: 62–64. 1995), karyological studies (e.g., Cook in Watsonia 5: 125. 1962; Dahlgren in Pl. Syst. Evol. 177: 201. 1991), papers on ecology of aquatic communities (e.g., Sarika-Hatzinikolaou & al. in Phytocoenologia 3: 101, 2003; Hrivnák & Csiky in Thaiszia 19: 76, 2009; Lumbreras & al. in Pl. Biosyst. 145(supp1.): 118. 2011; Lumbreras & al. in Acta Oecol. 52: 10. 2013), biochemical studies (e.g., Fiasson & al. in Biochem. Syst. Ecol. 25: 328. 1997; Murat & al. in Pharmacogn. Mag. 5: 292. 2009) as well as in various online databases (e.g., Euro+Med PlantBase, l.c.; Global Biodiversity Information Facility, l.c.; International Plant Names Index, l.c.; Plants of the World Online, l.c.; Tropicos, l.c.; World Flora Online, l.c.). The name R. rionii has been lectotypified recently as detailed above and its taxonomic identity confirmed (Kaplan & al. in PhytoKeys, in press). The recent examination of type specimens revealed that both the names Ranunculus bauhini and R. rionii refer to the same species, being taxonomic synonyms. Strict application of the priority rule would require the well-established name R. rionii to be replaced by the earlier name R. bauhini, which has never been adopted since its publication. However, this would be a typical example of resurrection of a long-forgotten name for purely nomenclatural reasons, which would cause an undesirable and disadvantageous change. To preserve nomenclatural stability for the species more than 170 years known as R. rionii, the name R. rionii should be conserved against the name R. bauhini. ZK, https://orcid.org/0000-0003-1707-7461 JP, https://orcid.org/0000-0003-4308-0824 PK, https://orcid.org/0000-0002-3455-850X We are grateful to the curators of the visited herbaria, who allowed us to study their collections, Sébastien Bétrisey, Vincent Sonnenwyl, Jacqueline Détraz-Méroz and Gregor Kozlowski for information on type material of R. rionii in NHMF and SION, and John McNeill and John Wiersema for helpful comments on the manuscript. The work was supported by grant no. 22-10464S from the Czech Science Foundation and by long-term research development project no. RVO 67985939 of the Czech Academy of Sciences.