(3089) Proposal to reject the name <i>Cactus tuna</i> ( <i>Opuntia tuna</i> ) ( <i>Cactaceae</i> )

(3089) Cactus tuna L., Sp. Pl.: 468. 1 Mai 1753 [Angiosp.: Cact.], nom. utique rej. prop. Lectotypus (vide Crook & Mottram in Bradleya 22: 61. 2004): [icon in] Dillenius, Hort. Eltham.: t. CCXCIX, fig. 380. 1732. Epitypus (vide Guiggi & Mariotti in Phytotaxa 573: 222. 2022): Jamaica, St. Andrew, Hope River valley, about 1 mi E of Mona, ca. 152 m alt., 12 Dec 1957, Yuncker 17727 (NY barcode 01496096). Cactus tuna was described by Linnaeus (Sp. Pl.: 468. 1753) with the note “Habitat in Jamaica & America calidiore” and the diagnosis: “CACTUS articulato: prolifer, articulis ovato-oblongis: spinis subulatis”. Additionally, Linnaeus cited three phrase names with six references: Cactus compressus articulatus ramosus, articulis ovato-oblongis, spinis subulatis (Linnaeus, Hort. Cliff.: 183, no. 14. 1738, Hort. Upsal.: 120, no. 8. 1748; Royen, Fl. Leyd. Prodr.: 280. 1740); Tuna major, spinis validis flavicantibus, flore gibbo (Dillenius, Hort. Eltham.: 396, t. 295, fig. “238”[?] [380]. 1732); and Opuntia major, folio oblongo rotundo: spinis longis & validissimis, flore luteo (Sloane, Cat. Pl. Jamaica: “103” [193]. 1696, Voy. Jamaica 2: 149, t. 224, fig. 1. 1725). Miller (Gard. Dict., ed. 8: Opuntia No. 3. 1768), when combining it as Opuntia tuna (L.) Mill. (see ICN Art. 41 Ex. 6; Turland & al. in Regnum Veg. 159. 2018), cited “articulis ovato-oblongis, spinis subulatis; Indian Fig with oblong oval joints, and awl-shaped spines” and also “Opuntia major, validissimis spinis munita” with a reference to Tournefort (Inst. Rei Herb.: 239. 1700), and added the statement “Greater Indian Fig with very strong spines.” Analyses of these materials led to the conclusion that Cactus tuna contains a mixture of elements (Crook & Mottram in Bradleya 22: 61. 2004; Mottram in Cactician 3: 65–69. 2013), with broad descriptions and mentions that correspond to distinct species as they are recognized today. Therefore, the concept of Opuntia tuna has been controversial within the specialized taxonomic literature on cacti. However, as “tuna” is a common vernacular name for many Opuntia species (= prickly-pear cacti) across its Latin-American natural range, the name O. tuna was occasionally applied, especially in the late 19th and early 20th century literature, and then sparsely used in broad catalogs, floras, or floristic treatments (see Howard & Touw in Cact. Succ. J. (Los Angeles) 54: 170–179. 1982; and references below). While early publications such as Salm-Dyck (Hort. Dyck.: 184–186. 1834), Pfeiffer (Enum. Diagn. Cact.: 161. 1837), Labouret (Monogr. Cact.: 458–459. 1853), and Bois (Dict. Hort.: 896. 1893) interpreted Opuntia tuna as a correct name for a species similar but different from O. elatior Mill. (l.c.: No. 4) and O. dillenii (Ker Gawl.) Haw. (Suppl. Pl. Succ.: 79. 1819, based on C. dillenii Ker Gawl. in Bot. Reg.: t. 255. 1818), citing occurrences from Quito [Ecuador], Mexico, and Colombia probably associated with elements from the Linnaean citation of Dillenius (l.c.), Schumann (Gesamtbeschr. Kakt.: 723–724. 1899) interpreted O. tuna as a correct name but different from the previous authors, recognizing O. dillenii as its synonym, likely based on the Linnaean references to Sloane (l.c. 1969, l.c. 1725). On the contrary, Mesa (Cact. Fl. Cubana: 39–40. 1912) and Britton & Rose (Cact. 1: 113–115. 1919) restricted the concept of O. tuna to a Jamaican plant different from O. elatior and O. dillenii, providing more specific information regarding morphology, distribution, and illustrations. Overall, this same concept was then adopted by Urban (Symb. Antill. 8: 466–467. 1921) and Fawcett & Rendle (Fl. Jamaica 5: 275–278. 1926), and generally followed but occasionally misapplied as in Barker & Dardeau (Fl. Haiti: 247. 1930), Backeberg & Knuth (Kaktus-ABC: 127–145. 1935), Backeberg (Die Cact. 1: 389–628. 1958, Kakteenlexikon: 307–334. 1966), Adams (Fl. Pl. Jamaica: 273–274. 1972), Howard & Touw (l.c.), Proctor (Fl. Cayman Islands: 320. 1984, ed. 2: 257. 2012), Anderson (Cact. Fam.: 484–525. 2001), and Acevedo-Rodríguez & Strong (Cat. Pl. West Indies: 192–202. 2012). In 2004, reviewing the Opuntia names, Crook & Mottram (l.c.) designated the figure from Dillenius (l.c.) as a lectotype. At that time, they wrote that Linnaeus's O. tuna “was mixed, containing elements of both tuna and dillenii” but continued to apply O. tuna as a species endemic to Jamaica and felt the Dillenius lectotype was this same species. However, due to the original mixture of elements and uncertainties regarding the plant illustrated in the lectotype, O. tuna was still treated as having an uncertain application by the contemporary and influential Cactaceae treatment of Hunt & al. (New Cact. Lex.: 196–214. 2006). More recently, Guiggi & Mariotti (in Phytotaxa 573: 215–230. 2022) reassessed the identity of O. tuna as an earlier name for O. dillenii, and selected an epitype consistent with the traditional usage of O. dillenii. Additionally, they proposed a new name, O. kingstoniana Guiggi, for the species endemic to Jamaica, which had previously been referred to as O. tuna (cf. Britton & Rose, l.c.). Despite some still debated issues regarding the taxonomic status of Opuntia stricta (Haw.) Haw. (Syn. Pl. Succ.: 191. 1812, based on C. stricta Haw., Misc. Nat.: 188. 1803) and O. dillenii, which was eventually regarded as a variety of the former (e.g., Benson, Cacti U.S. Canada: 910–933. 1982), O. dillenii is an extensively applied and accepted name used for one of the most common and widespread prickly-pears native to the Caribbean islands and some adjacent coasts of the American continent, being treated in many works (Pfeiffer, l.c.; Mesa, l.c.; Britton & Rose, l.c.; Britton & Millspaugh, Bahama Fl.: 295–297. 1920; Berger, Kakteen: 77. 1929; Barker & Dardeau, l.c.; Backeberg & Knuth, l.c.; Backeberg, l.c. 1958, l.c. 1966; Adams, l.c.; Howard & Touw, l.c.; Howard & Bornstein, Fl. Lesser Antilles 5: 410–415. 1989; Innes & Glass, Ill. Encycl. Cacti: 211. 1997; Anderson, l.c.; Acevedo-Rodríguez & Strong, l.c.; Korotkova & al. in Willdenowia 51: 251–270. 2021). Additionally, O. dillenii is nowadays a taxon of concern, as it has been introduced worldwide and cultivated, treated in floras from other continents (e.g., Telford, Fl. Australia 4: 62–80. 1984; Li & Taylor in Wu & al., Fl. China 13: 209–212. 2007), and reported (as a species or a variety of O. stricta) as an invasive taxon in global databases (such as the Global Invasive Species Database, accessed 27 Jan 2025, managed by the Invasive Species Specialist Group [ISSG] of the International Union for Conservation of Nature [IUCN]) or in countries like Brazil (Instituto Hórus, Base de Dados Nacional de Espécies Exótivas Invasoras, accessed 27 Jan 2025), Madagascar (Kull & al. in Biol. Invas. 14: 875–888. 2012), South Africa (Henderson, Invas. Alien Pl. S. Africa: 160–332. 2020), and in Mediterranean countries (i.e., Italy, Spain, Portugal; see Essl & Kobler in Flora 204: 485–494. 2009). Consequently, Guiggi & Mariotti's (l.c.) proposal resulted in significant disruption, upending the application of Opuntia tuna, and displacing the use of O. dillenii, names that had been in use for over 100 years for a Jamaican endemic and over 200 years for a widespread (and now worldwide) Caribbean taxon, respectively. Additionally, it is clear that the epitype designated for O. tuna differs greatly from its lectotype, especially regarding the number of areoles, which is much higher in the lectotype illustration as compared to the epitype, adding new grounds for confusion. As noted by Piñeyro & al. (in Haseltonia 30: 84. 2023), the lectotype has a bluish-green cladode, long-elliptic to obovate with subentire margins, broadly rounded at the apex and acute at the base, ca. 19–23 areoles on one face of the cladode not including the marginal areoles with straight spines (5–7) overlapping or nearly reaching spines of adjacent areoles, and also, unlike C. dillenii, a dark red acute flower bud and a green stigma; while the epitype has a short obovate cladode with angular margins, ca. 6 areoles far apart from each other on the face, few curved spines (1–3) burnt yellow to gold-brownish, and light green epidermis. The epitype is a specimen that perfectly matches the broadly used concept of O. dillenii, which was lectotypified by Benson (in Cact. Succ. J. (Los Angeles) 41: 126. 1969) with the illustration in Ker Gawl. (l.c.). On the contrary, the lectotype illustrates a specimen of uncertain application, certainly not O. dillenii, but potentially related to O. elatior. In fact, the Linnaean protologue of Cactus tuna cites his Hortus Cliffortianus, in which he cited a Dillenius figure (l.c.: 395, t. 294, fig. 379) that was Miller's only included element of O. elatior. In one of his last contributions, the late Roy Mottram (l.c.) concluded that O. tuna had clearly a mixture of elements from at least O. dillenii and O. elatior, and listed O. elatior as a synonym of O. tuna. So we are faced with quite a conundrum with the name Opuntia tuna. Following Britton & Rose (l.c.), it is an endemic species of Jamaica. The lectotype illustration is of uncertain application, potentially related to O. elatior. The epitype of the name O. tuna is O. dillenii, and likewise the Sloane (l.c. 1725) illustration of O. tuna is O. dillenii. The best solution to the problem is to answer this question: what would best serve nomenclatural stability and the application of the names across the community? Undoubtedly, the name O. dillenii has been widely adopted, with 4600 citations in Google Scholar (accessed 18 Feb 2025) just since 2000, and its use should be preserved to avoid displacing a well-established name for purely nomenclatural reasons. On the contrary, despite occasionally being present in the literature (ca. 550 citations in Google Scholar over the same period), O. tuna is a name historically filled with different interpretations and controversial applications. Then, to retain the names that best serve the stability of nomenclature, we propose to reject the name O. tuna to (1) preserve the use of the name O. dillenii for the widespread taxon from the Caribbean region, as has been done in the last 200 years in numerous floras and catalogs; and to (2) allow the application of the name O. kingstoniana to the species endemic to Jamaica previously circumscribed as O. tuna by some authors. If this proposal is rejected, then O. tuna will remain a name with an epitype that is not conspecific with its lectotype and that threatens the application of O. dillenii. As an alternative, O. tuna could be proposed to be conserved with a conserved type that would restrict its use to the Jamaican endemic species. However, we believe that such a procedure would only add to the confusion over the interpretation of the name O. tuna. We are grateful to John H. Wiersema for his valuable editorial suggestions that improved this manuscript. MK is thankful to the National Council for Scientific and Technological Development – CNPq (Brazil, process 150026/2024-2) for supporting this research.

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