(2717) Proposal to reject the name <i>Iris biflora</i> (<i>Iridaceae</i>)

(2717) Iris biflora L., Sp. Pl.: 38. 1 Mai 1753 [Angiosp.: Irid.], nom. utique rej. prop. Typus: non designatus. In 1753, Linnaeus (Sp. Pl.: 38. 1753) published the name Iris biflora, with a descriptive polynomial from his earlier work (Linnaeus, Hort. Upsal.: 17. 1748), followed by two polynomial synonyms. The first synonym, “Iris corollis barbatis, foliis caulem multiflorum superantibus”, was cited from another previous work (Hort. Cliff.: 19. 1738) and from Van Royen (Fl. Leyd. Prodr.: 17. 1740), and the second one, “Chamaeiris major saturate purpurea biflora”, was taken from Bauhin (Pinax: 33. 1623). The protologue also includes the provenance “Habitat in Lusitaniae [Portugal]”, along with the habitat “rupibus [on rocks]”. No illustrations were provided in Bauhin (l.c.), Linnaeus (l.c. 1738, 1748), or Van Royen (l.c.). The two Linnaean references (Linnaeus, l.c. 1738, 1748) contain the information that the species occurred on rocks near the sea (“rupibus maritimis”) in Lusitania (Portugal) and note that the etymology of the specific epithet biflora is connected to the fact that the plant flowered twice in a year. This information was derived from Clusius (Rar. Stirp. Hispan. Hist.: 282–284. 1576), who described and illustrated plants that grew above the River Tagus in Portugal not far from Coimbra and that were flowering in November and were said to have also flowered in the spring; for that reason he termed his account of the species “De Iride Lusitanica seu biflora” and adopted the name “Iris biflora”, stating “Bifloram nuncupavi [I have named it biflora]”, the binomial later validated by Linnaeus (l.c. 1753). According to Jarvis (Order out of Chaos: 594. 2007), the name I. biflora was still to be typified, and the only extant potentially original material for this name was the specimen No. 61.4 from the Linnaean Herbarium held at LINN. This is still the case. The specimen LINN No. 61.4 (image available at http://linnean-online.org/801/) is undoubtedly original material for I. biflora because of the occurrence on the sheet of the Linnaean annotation “5 biflora”, where “5” refers to the Species plantarum number of this species. This specimen consists only of the above-ground part of a single plant with basal leaves and two flowering stems (one of which is branched) to 13 cm long; the stems have two short, slightly broadened bracts (ca. 4.5 cm long), and bear flowers with pedicels to 1.5 cm long, and a short perianth tube. As suggested by Dykes (Genus Iris: 158. 1912) and confirmed in the present study, the sheet LINN No. 61.4 is identifiable as I. aphylla L. (Sp. Pl.: 38. 1753), a widely recognised species. However, some authors (Dykes in Gard. Chron., ser. 3, 47: 146. 1910; Dykes, l.c. 1912: 146, 158–159; Mathew, Iris, ed. 2: 24. 1989) have treated the name I. biflora as a nomen confusum as it was considered to include elements belonging to more than one species (see below). It is worth mentioning that the specimen at LINN (No. 61.1) with the Linnaean annotation “6 pumila” is not identifiable as I. pumila L. (Sp. Pl.: 38. 1753) as that name is currently applied and as it has been recently typified (Boltenkov in Willdenowia 49: 148–150. 2019) but is referable to I. lutescens Lam. (Encycl. 3: 297. 1789); moreover, the true I. aphylla is not represented by an originally labelled element in the Linnaean and Linnaean-linked herbaria (Colasante & Mathew in Pl. Biosyst. 142: 176. 2008; Boltenkov in Phytotaxa 273: 141. 2016). All things considered, it seems that Linnaeus might have confused or mixed up herbarium specimens of I. aphylla, I. biflora, and I. pumila. On the basis of the Linnaean protologue, Dykes (l.c. 1912: 145) synonymised I. biflora “in part only” under both I. subbiflora Brot. (Fl. Lusit. 1: 50, t. 96. 1804), which in recent times has been included in I. lutescens sometimes as a subspecies (see Webb & Chater in Bot. J. Linn. Soc. 76: 316. 1978), and I. aphylla (Dykes, l.c. 1912: 157). Given that there is no clear morphological, ecological, or geographical separation between I. subbiflora (I. biflora L. pro parte et sensu auct. pl.) and I. lutescens (see Crespo in Castroviejo & al., Fl. Iber. 20: 412–415. 2013) we deem it appropriate to treat both these names as referring to a single species. Whereas the protologue and the references that include habitat details of I. biflora (Linnaeus, l.c. 1738, 1748) refer only to its occurrence in “Lusitania”, three of the cited publications (Bauhin, l.c.; Linnaeus, l.c. 1738, 1748) include as a synonym “Chamaeiris latifolia biflora” from Besler (Hort. Eystett. 1613). The other cited publication (Van Royen, l.c.) also refers to this synonym but indirectly through Boerhaave (Ind. Alter Hort. Lugd.-Bat. 2: 125. 1720). Besler's publication is arranged in four classes according to the season, each with orders within it and the plates numbered within each order. “Chamaeiris latifolia biflora” is in Classis 1 Verna, Ord. 8, fol. 1, fig. 4 [on reverse of title page of Ord. 8] (Besler, l.c.), and this illustration undoubtedly represents the Central European I. aphylla and not the Portuguese plant (I. subbiflora or I. lutescens), a form of which is depicted under the name Iris portugalica by Besler (l.c. Ord. 8, fol. 6, fig. 2 [on reverse of text of fol. 5]). Based on those facts, Dykes (l.c. 1912) disregarded I. biflora in favour of both I. aphylla for the Central European plant and I. subbiflora for the southwestern Mediterranean one, as later Webb & Chater (in Tutin & al., Fl. Eur. 5: 90, 424. 1980) did, but treating the latter as I. lutescens subsp. subbiflora (Brot.) D.A.Webb & Chater (l.c. 1978). However, other authors (Mathew, l.c.; Service in Species Group of the British Iris Society, Guide Spec. Irises: 22, 46, 53. 1997) alternatively referred I. biflora partly to I. aphylla and partly to the Eastern European I. pumila and, in the case of Service, also partly to I. subbiflora; the assignment to I. pumila is not, in our opinion, supported by either the material at LINN or any element in the protologue. Dykes's treatment has usually been adopted by later authors, and is essentially followed here but including I. subbiflora in I. lutescens. In fact, synonymisation of I. biflora and I. subbiflora had traditionally been assumed by taxonomists for many previous decades in both general works and monographs (e.g., Sprengel, Syst. Veg. 1: 162. 1825; Nyman, Consp. Fl. Eur. 4: 701. 1882; Baker, Handb. Irid.: 88. 1892; Lynch, Book Iris: 132. 1904), probably based on geographical indications in the protologues of both names. Iris lutescens is a rhizomatous perennial with leaves present through the winter, evident flowering stem (to 35 cm long) with 1–2 flowers, very short pedicels, short perianth tube (2–4[–4.8] cm long), and inflated and membranous bracts (3–5.5[–10] cm long). It is native to southern Europe, extending from Portugal to northwestern Italy, and possibly to North Africa (Morocco); it grows in dry places. The name I. lutescens was typified by Crespo (in Flora Montiber. 53: 52. 2012) and has consistently been accepted and is referenced in numerous publications including almost all contemporary literature (e.g., Rechinger, Fl. Aegaea: 741. 1943; Webb & Chater, l.c. 1980; Mathew, l.c.: 31; Service, l.c.; Crespo, l.c. 2013; Peruzzi in Pl. Biosyst. 152: 192. 2018). Iris biflora was preferred for this species mostly in older literature (e.g., Bergius, Mater. Med. 1: 42. 1782; Lamarck, Encycl. 3: 295. 1789; Roemer & Schultes, Syst. Veg. 1: 462. 1817; Ker Gawler, Irid. Gen.: 57–58. 1827; Coutinho, Fl. Portugal: 146. 1913; Bailey, Stand. Cycl. Hort.: 1670. 1915). However, the Linnaean Typification Project checklist of Linnaean plant names (https://www.nhm.ac.uk/our-science/data/linnaean-typification/index.html) lists I. biflora as an accepted name. In summary, the name I. biflora has either been rejected as confused in its application or used in contrasting ways almost from its description, and for most of this time in a sense that disagrees with the only extant original Linnaean element (LINN No. 61.4). Therefore, rejection of the name I. biflora as proposed here would have the positive effect of ending the nomenclatural conflict in a manner that maintains current usage of the relevant names. Should I. biflora be formally typified on LINN No. 61.4, it would have priority over I. aphylla and would thus apply to a species with which the name has not been associated in recent times. Indeed, only a very few authors (e.g., Sweet, Brit. Fl. Gard. 5: t. 152. 1832; Reichenbach, Icon. Fl. Germ. Helv. 9: 4, t. 332. 1847) appear to have used I. biflora in the sense of I. aphylla and not since the middle of the 19th century. Proposing I. biflora for conservation with a conserved type that would restore its historic application to the Portuguese species is also inappropriate as this would make it a heterotypic synonym of I. lutescens with priority over it. Either of these actions would threaten well-known and currently stable names of widespread European species, I. aphylla and I. lutescens. While it would be possible to propose conservation of I. aphylla against a lectotypified I. biflora, we consider outright rejection of I. biflora under Art. 56 of the Shenzhen Code (Turland & al. in Regnum Veg. 159. 2018) a more straightforward solution, as it avoids the need for a typification that conflicts with current usage. Acceptance of this rejection proposal would preserve the use of both I. aphylla and I. lutescens in their traditional concepts and is in line with the actions of previous authors who rejected I. biflora as a nomen confusum (Dykes, l.c. 1910, 1912; Mathew, l.c.) or as a nomen ambiguum (Webb & Chater, l.c. 1980: 424), and has the additional advantage that it precludes the need for undesirable typification. Any alternative, either the obligate lectotypification or a conservation proposal, would force a change in name for one of the two well-known species names discussed above in favour of I. biflora that, as far as we are aware, has never been used in an original publication since 1915 (Bailey, l.c.). EVB, https://orcid.org/0000-0002-7310-659X MBC, https://orcid.org/0000-0002-3294-5637 We are very grateful to Mark Spencer (Natural History Museum, London) for helping with the Iris specimens from LINN, Charles Jarvis (Natural History Museum, London) for the comments about Linnaean names in Iris, and to John McNeill (Royal Botanic Garden, Edinburgh, Scotland, U.K. & Royal Ontario Museum, Toronto, Ontario, Canada) for his editorial comments and wise suggestions.

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