(2946) Proposal to conserve the name <i>Iris latifolia</i> (Mill.) Voss (<i>Iridaceae</i>) against <i>I. latifolia</i> Heer (fossil <i>Iridaceae</i>)

(2946) Iris latifolia (Mill.) Voss, Vilm. Blumengärtn., ed. 3, 1: 982. 1895 (Xiphion latifolium Mill., Gard. Dict., ed. 8: Xiphion No. 3. 16 Apr 1768) [Angiosp.: Irid.], nom. cons. prop. Typus: [icon] “Iris bulbosa flore diluto coeruleo” in Besler, Hort. Eystett. 2 (Classis Aestiva), Ord. 4, fol. 9, fig. 1. 1613. (H) Iris latifolia Heer, Mioc. Balt. Fl.: 29. 15 Nov 1869 [Foss.], nom. rej. prop. Typus: non designatus. Due to an apparent lack of penetration of the palaeobotanical literature in systematic botany, recent addition of names of fossil plants to comprehensive databases of plant names (i.e., IPNI, IFPNI, POWO, etc.) is revealing the existence of homonymy problems affecting names in current use of extant plants in diverse taxonomic groups (see Mill in Taxon 51: 185–186. 2002; Ungricht & al. in Taxon 53: 566–568. 2004). The present conservation proposal under Art. 14 of the ICN (Turland & al. in Regnum Veg. 159. 2018) deals with two homonyms in the genus Iris L. The earlier, Iris latifolia Heer, applies to a fossil plant described from northern Europe in the second half of the 19th century, whilst the later, Iris latifolia (Mill.) Voss (Xiphion latifolium Mill.), applies to the renowned “English iris”. In accordance with Art. 53, later homonyms are illegitimate whether the type is fossil or non-fossil (Art. 11 Note 5), and therefore the former name is legitimate and the latter one is illegitimate. For those who prefer using the name Xiphion latifolium Mill. for the English iris, this proposal has no relevance. Oswald [von] Heer (1809–1883), a Swiss palaeobotanist and entomologist, professor at the University and the Swiss Federal Institute of Technology (ETH) in Zürich, described Iris latifolia Heer (Mioc. Balt. Fl. [Beitr. Naturk. Preuss. 2]: 29. 1869) based on fossil leaf fragments collected in the former eastern Prussian Samland, near Kraxtepellen (currently, Yantarnyj) and Rauschen (currently, Svetlogorsk), in Kaliningrad Oblast, Russia. A holotype was not designated in the protologue, and a later lectotypification is not known to the present authors. The original material consists of six incomplete (and rather heterogeneous) fossilised fragments of leaves (Heer, l.c. 1869: t. 4, fig. 1–6), the largest about 22 × 4 cm, that apparently gave rise to the specific epithet. The diagnostic sentence “I[ris]. foliis firmis, latissimis, ensatis (?), irregulariter striatis” was added, together with a brief description of the type material. Images of any other vegetative or reproductive structure are lacking in the protologue. One year later, Heer (in Kongl. Svenska Vetensk.-Akad. Handl., n. s., 8(7): 53–54, t. 8, fig. 1–4a, t. 9. 1870) cited again this plant from Spitsbergen (currently, Svalbard Archipelago, Norway) in the Arctic Sea, and illustrated some new fossilised material including supposed fragments of leaves (again rather heterogeneous), stems, a (likely) seed and part of a rhizome. Apart from its mention in a classic German palaeobotany textbook by Schenk (Handb. Palaeont., Palaeophyt.: 364. 1885), within the 19th century only occasional references appear to have been made to that fossil iris, and not much further information has become available since. Moss (in Cole & al., Mem. Geol. Surv. Ireland (Interbasaltic Rocks): 103–111. 1912) assigned to Iris latifolia Heer with doubt some fossil reed-like leaf remains found in Ballypalady, County Antrim (Northern Ireland). The same name was applied by Engelhardt (Alttert. Fl. Messel: 28. 1922) to fossil leaf fragments from Messel, near Darmstadt (Hesse, western Germany), and by Manum (in Norsk Polarinst. Skr. 125: 81, 91. 1962) to fossilised leaves and rhizomes found in Spitsbergen, and it was also listed by Budantsev & Sveshnikova (in Trudy Bot. Inst. Komarova Akad. Nauk SSSR, ser. 8, Paleobot. 5: 81–112. 1964) in a series of critical notes to the Tertiary flora of the Kaliningrad Peninsula. It is worth mentioning that Moss (l.c.: 109) referred to the Antrim fossils he studied as follows: “The reed-like impressions have received various names, e.g., Iris latifolia; but it may be said at once that the impressions are of such a nature that any suggestion of a positive nature in untenable which states more than that they are probably the impressions of the leaves of some Monocotyledons.” Indeed, on the basis of its morphological characteristics, the type material of I. latifolia Heer might also be assigned, if not to other monocotyledonous families, perhaps to other close iridaceous genera with similar leaf structure, such as Gladiolus L. Eventual transfer of Heer's taxon to this genus would require a replacement name, because of the existence of the previous and validly published Gladiolus latifolius Lam. Iris latifolia (Mill.) Voss (Vilm. Blumengärtn., ed. 3, 1: 982. 1895), based on Xiphion latifolium Mill. (Gard. Dict., ed. 8: Xiphion No. 3. 1768), which was lectotypified by Crespo (in Fl. Montiber. 53: 57. 2012), is a Cantabrian-Pyrenean species, endemic mostly to the northern third of the Iberian Peninsula, from Sierra de Guadarrama (central Spain) and Picos de Europa (northwestern Spain) to the Eastern Pyrenees, reaching their French side. There, it is widely distributed from sea level up to 2400 m elevation, occurring in open grasslands and meadows in both calcareous or schistose substrates under humid climate (Crespo in Castroviejo & al., Fl. Iber. 20: 436–437. 2013). However, wild populations are becoming rare and scarce in some parts of its native area, and consequently it has been included as vulnerable (VU) in the catalogue of the threatened vascular flora of País Vasco, northern Spain (Aizpuru & al., Lista Roja Fl. Vasc. CAPV: 177–178. 2010), according to the IUCN red list categories and criteria (2012). This name is currently in use and accepted in national and local floras (e.g., Webb & Chater in Tutin & al., Fl. Eur. 5: 91. 1980; Zubía, Fl. Rioja, ed. 2: 228. 1993; Aizpuru & al., Claves Ilustr. Fl. País Vasco y Territor. Limítr.: 135. 1999; Bolòs & Vigo, Fl. Països Catalans 4: 153–154. 2001; Villar & al., Atlas Fl. Pirineo Aragon. 2: 446. 2001; Tison & al., Fl. France Medit. Cont.: 264. 2014; Jiménez-Alfaro & al. in Mediterr. Bot. 42: e74570. 2021), or it is treated as the alternative priority synonym for Xiphion latifolium when both genera are regarded as distinct (e.g., Crespo, l.c. 2013; Lorda, Cat. Floríst. Navarra: 124. 2013; Durán in Monogr. Bot. Iber. 13: 301. 2014). It is a very popular plant known among horticulturists as the English iris, of which several cultivars have been selected (see Dykes, Gen. Iris: 211–213. 1912, under I. xiphioides Ehrh.; Mathew, Iris: 136. 1981; Christiansen in Sp. Group Brit. Iris Soc. (ed.), Guide Iris.: 222–223. 1997) and are mostly grown as garden plants and for cut-flower bouquets. Sometimes it escapes from cultivation, and is currently listed in the Global Register of Introduced and Invasive Species (GRIIS) as alien in Norway since 2004 (Sandvik & al. in Biol. Invas. 21: 2997–3012. 2019). The name Iris latifolia (Mill.) Voss is broadly accepted on influential websites, such as The American Iris Society (https://wiki.irises.org/Spec/SpecLatifolia), the Catalogue of Life-CoL (http://www.catalogueoflife.org/annual-checklist/2011/details/species/id/8156094), the Euro+Med PlantBase (http://ww2.bgbm.org/EuroPlusMed/PTaxonDetail.asp?NameCache=Iris%20latifolia&PTRefFk=8000000), the European Network on Invasive Alien Species-NOBANIS (https://www.nobanis.org/species-info/?taxaID=12996), the NCBI-GenBank (https://www.ncbi.nlm.nih.gov/Taxonomy/Browser/wwwtax.cgi?id=889463), the Pacific Bulb Society (https://www.pacificbulbsociety.org/pbswiki/index.php/SpanishIrises#latifolia), the Pan-European Species directories Infrastructure-PESI (http://www.eu-nomen.eu/portal/taxon.php?GUID=4147104A-BFDB-40EA-835F-7DF83A94A7D4), Tela Botanica-France (https://www.tela-botanica.org/bdtfx-nn-35931-synthese), and also in Wikipedia (https://en.wikipedia.org/wiki/Iris_latifolia), all accessed 18 Jan 2023. Furthermore, it has also been included until very recently in Plants of the World Online-POWO (https://powo.science.kew.org/) as the accepted name for Xiphion latifolium Mill. in Iris, but it is now referred to as an illegitimate name (as a later homonym of Heer's name) to be replaced by an apparently still unpublished combination “Iris jacquinii (Schrank) ined.” (Xiphion jacquinii Schrank in Flora 7(2, Beibl.): 17. 1824). The Global Biodiversity Information Facility-GBIF (https://www.gbif.org/species/5297960) also treats this name similarly. A Google Scholar string search (18 Jan 2023) for “Iris latifolia (Mill.) Voss” returned 50 results, whereas a similar search for “Iris latifolia Heer” returned only 3. Far more numerous results are obtained from Google searches for the strings “Iris latifolia” coupled with either “English iris” or “lirio azul”, the latter a common name in its native range. A high percentage of those returned entries correspond to gardening sites, in which information on cultivation and/or bulb and seed sale are found, testifying to the widespread usage of this name for an ornamental plant. The rationale for the present conservation proposal is based on the same three arguments used by Ungricht & al. (l.c.) in their proposals to conserve three junior names in Ficus L. (Moraceae) under Art. 14, which were favourably voted by the Committee for Fossil Plants (Skog in Taxon 54: 827. 2005) and are now conserved. These arguments are: (i) uncertainty concerning the identity of the fossil plant (i.e., its placement in the genus Iris might be debatable); (ii) past and current usage of both homonymous names in systematic and floristic literature (including databases and the Internet) shows that the extant iris name is being applied far more frequently; and (iii) past and current usage of the extant iris name occurs beyond systematics and floristics (i.e., in horticulture, ecology, and plant conservation). Moreover, the name of the extant iris is connected to significant input to the local economy of several countries. Therefore, for these reasons, we formally propose to conserve Iris latifolia (Mill.) Voss against I. latifolia Heer to avoid disadvantageous nomenclatural changes and best serve stability of nomenclature. Acceptance of the present proposal would preserve the use of the well-established I. latifolia (Mill.) Voss in its traditional concept, and would eliminate the need for an unnecessary new combination, “I. jacquinii (Schrank) ined.”, for the popular English iris. Conversely, maintaining the name I. latifolia Heer for the fossil plant would create undesirable nomenclatural instability and add unnecessary confusion to botanists, horticulturists, and plant conservationists. MBC, https://orcid.org/0000-0002-3294-5637 AC, https://orcid.org/0000-0002-5090-7730 We are very grateful, as always, to John Wiersema (Department of Botany, Smithsonian Institution, Washington, D.C., U.S.A.) and John McNeill (Royal Botanic Garden, Edinburgh, Scotland, U.K. & Royal Ontario Museum, Toronto, Ontario, Canada) for their editorial comments and wise suggestions.

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