(2808) Proposal to reject the name Acalypha supera (Euphorbiaceae)

Abstract

(2808) Acalypha supera Forssk., Fl. Aegypt.-Arab.: 162. 1 Oct 1775 [Angiosp.: Euphorb.], nom. utique rej. prop. Typus: non designatus. The name Acalypha supera was established by Forsskål (Fl. Aegypt.-Arab.: 162. 1775) by means of a short description. In the protologue, he noted that his new species resembled A. indica L. (Sp. Pl.: 1003. 1753) but lacked bracts, which he suggested might have fallen off. Forsskål's notes indicate that he saw the plant in Yemen, but unfortunately he did not designate a type, and no potential type material has been found in the Forsskål Herbarium at C or elsewhere, and no one has ever reported seeing any original material (Christensen in Dansk Bot. Ark. 4: 28. 1922; Hepper & Friis, Pl. Forsskål's Fl. Aegypt.-Arab.: 152. 1994). Poiret (in Lamarck, Encycl. 6: 207. 1804) discussed the status of Acalypha supera, stating that he believed it to be A. indica except for the absence of female bracts, but that seeing a specimen would be necessary to confirm its identity. Steudel (Nomencl. Bot. 1: 4. 1821; ed. 2, 1: 10. 1840) merely noted Poiret's uncertain treatment. Müller (in Linnaea 34: 45. 1865; in Candolle, Prodr. 15(2): 870. 1866) tentatively synonymized it with A. brachystachya Hornem. (Enum. Pl. Hort. Hafn., rev. ed.: 1. 1807), writing in his latter work, “Hic etiam pertinere videtur A. supera Forsk.” The few other botanists who mentioned A. supera over the succeeding 134 years (Schweinfurth in Bull. Herb. Boissier 7, App. II: 309. 1899; Christensen, l.c; Pax & Hoffmann in Engler, Pflanzenr. IV. 147 XVI (Heft 65): 101. 1924; Schwartz, Fl. Trop. Arab.: 138. 1939; Hepper & Friis, l.c.; Govaerts, World Checkl. Seed Pl. 1(1): 42, 1(2): 47. 1995) followed Müller's lead, usually indicating equal uncertainty. Only in 2000 was it first accepted, without explanation, as the correct name for the species previously called A. brachystachya (Govaerts & al., World Checkl. Euphorb. 1: 90. 2000). Since 2000, Acalypha supera has been accepted as the name for this species in a few subcontinental or national floras and checklists, such as Lebrun & Stork (Fl. Pl. Trop. Africa 2: 24. 2006), Sosef & al. (in Scripta Bot. Belg. 35: 58. 2006); Figueiredo & Smith (in Strelitzia 22: 70. 2008), Qiu & Gilbert (in Wu & al., Fl. China 11: 252. 2008), and Pickering & Darbyshire (in Darbyshire & al., Pl. Sudan S. Sudan: 216. 2015). During the same period, the name A. brachystachya has been used for this taxon in the following subcontinental or national floras and checklists: Boufford & al. (in Huang & al., Fl. Taiwan, ed. 2, 6: 68. 2003), Ngernsaengsaruay & Chayamarit (in Santisuk & Larsen, Fl. Thailand 8: 23. 2005), Klopper & al. (Checkl. Fl. Pl. Sub-Saharan Africa: 274. 2006), Balakrishnan & Chakrabarty (Fam. Euphorb. India: 24. 2007), Sagun & al. (in Blumea 55: 35. 2010), Barberá & al. (in Phytotaxa 140: 3. 2013), and Cardiel & Montero Muñoz (in Pl. Syst. Evol. 304: 99. 2017); it has also been used in multiple checklists for smaller areas (for examples, see list in Govaerts & al., World Checkl. Euphorb., https://wcsp.science.kew.org). It is also notable that several online nomenclatural databases (Govaerts & al., l.c., accessed 18 Jan 2021; Plants of the World Online, http://powo.science.kew.org, accessed 18 Jan 2021; and checklists based on these) accept A. brachystachya, although admittedly this almost certainly reflects our note (Sagun & al., l.c.) that we would be proposing rejection of A. supera. Forsskål's description of Acalypha supera is, in our opinion, not diagnostic, a view also shared by Balakrishnan & Chakrabarty (l.c.) and Cardiel & Montero Muñoz (l.c.), who also have significant expertise in Acalypha. The description focused primarily on vegetative characteristics, which are consistent with several annual Acalypha species; those that are found in the parts of northeastern Africa and southwestern Asia where Forsskål traveled are A. brachystachya and A. indica, so it makes sense that these are the species with which subsequent botanists associated it. Regarding the reproductive characters, he wrote only “amentis axillaribus masculis, flore foemineo pedicellato, terminatis” and, as we noted above, that the plant he saw might have lost its female bracts. Both A. brachystachya and A. indica have axillary, androgynous inflorescences (bisexual with proximal female flowers and distal male ones), and neither sheds the female bracts, which are the most reliable way to distinguish the two species. Unlike the well-spaced, subentire, conspicuous bracts of A. indica, those of A. brachystachya are tightly clustered at the base of the inflorescence, deeply lobed, and inconspicuous when young, so it is possible that Forsskål misinterpreted them as being absent. Indeed, Hornemann originally, but incorrectly, described A. brachystachya as lacking bracts. Why Forsskål did not see the proximal female flowers is mysterious (all the herbaceous Acalypha species in northeastern Africa and Yemen have androgynous inflorescences). Both A. brachystachya and A. indica also produce solitary, terminal, pedicellate female flowers (allomorphic flowers sensu Radcliffe-Smith in Kew Bull. 28: 525–529. 1973); however, the pedicels in A. brachystachya are 0.5–0.75 mm long, so are much less likely to have drawn Forsskål's attention than those of A. indica, which are 3.5–15 mm long. It is also relevant that no specimens of A. brachystachya are known from Yemen, and recent floras exclude it from there (Wood & Haig-Thomas, Handb. Yemen Fl.: 190. 1997; Al Khulaidi, Fl. Yemen: 99–100. 2000). The only reports of A. brachystachya from Yemen (Schweinfurth, l.c.; Schwartz, l.c.; Govaerts & al., l.c. 2000 & https://wcsp.science.kew.org, accessed 18 Jan 2021) are based on the assumption that it and A. supera are synonyms. In contrast, A. indica is well-documented from Yemen. In summary, ambiguity about the application of the name Acalypha supera cannot be resolved because no original material is known; we cannot support neotypification because no known species of Acalypha fully agrees with the protologue. Accepting A. supera as synonymous with A. brachystachya is nomenclaturally destabilizing because it replaces a long-accepted name for a weedy species found throughout sub-Saharan Africa and much of subtropical and tropical Asia, and that recently has become established in the Canary Islands (Núñez & al. in Bot. Macaronés. 28: 167. 2013), with a name that has seen only occasional use in the last 20 years. (If treated as a synonym of A. indica, A. supera has no nomenclatural impact because it lacks priority, but for reasons we cannot explain, no one has made this interpretation since the 1840s.) We therefore propose rejection of the name Acalypha supera under Art. 56 (Turland & al. in Regnum Veg. 159. 2018). GAL, https://orcid.org/0000-0003-1514-1570 VGS, https://orcid.org/0000-0002-5348-0648 We thank Barney Lipscomb, Botanical Research Institute of Texas, for bibliographic help when most libraries were closed due to the COVID-19 pandemic. We are grateful to John McNeill and John Wiersema for their editorial comments. Lynn Gillespie provided valuable comments on an early version of the paper. This work received support from a grant from the United States National Science Foundation (DEB-0128872) to GAL.