TAXON 66 (6) • December 2017: 147^1–1472 Chen • (2567) Conserve Acer heptaphlebium

Proposal to conserve the name Acer heptaphlebium against A. taiwanense (Aceraceae)
You-Sheng Chen State Key Laboratory of Systematic & Evolutionary Botany, Institute of Botany, Chinese Academy of Sciences. 20 Nanxincun, Xiangshan, Beijing 100093, China; maple@ibcas.ac.cn DOI https://doi.org/10.12705/666.18

Acer heptaphlebium Gagnep. in Notul. Syst. (Paris) 13: 194. Jan 1948, nom. cons. prop. Typus: Tonkin [Vietnam]. prov. Vinh-yen [Vinh Phuc], Tam- dao [Tam Dao], 29 Apr 1931, Casalta, comm. Brillet 4 (P bar- code P05212498). (=) Acer taiwanense Yamam. in J. Soc. Trop. Agric. 5: 180. 1933, nom. rej. prop. Holotypus: [Vietnam, Vinh-yen], Tam dao, 1 Aug 1917, [Hayata] (TAI No. 118952).

Acer heptaphlebium Gagnep is a species endemic to Vietnam and Laos (Gagnepain in Notul. Syst. (Paris) 13: 192–195. 1948; Gagnepain in Lecomte, Fl. Indo-Chine Suppl. 1: 909–1027. 1950; Hô, Ill. Fl. Viet- nam 2: 414. 1992; Gibbs & Chen, Red List Maples: 17. 1999; Truong, Checkl. Pl. Sp. Vietnam: 137. 2003).
In the protologue Gagnepain (l.c. 1948) cited collections from four different localities in the French colonial territories of Tonkin (northern Vietnam), Annam (central Vietnam) and Laos, but did not designate a type. Although a flowering specimen in the Muséum National d’Histoire Naturelle in Paris labelled “Herbier Forestiere Tonkin”, numbered “4”, and collected by “Casalta” on 13 Oct 1931 from Tam-dao in Vinh Phuc Province in northern Vietnam (barcode P05212496) was annotated in 1976 as lectotype of Acer heptaphlebium, no lectotypification has ever been effectively published.
At the same time a second specimen, also numbered “4” on the “Herbier Forestiere Tonkin” label and collected by “Mr Casalta”, but with an additional printed label “M. Brillet Pl. du Tonkin”, was annotated as isotype but as it is a fruiting specimen dated 29 Apr 1931, it cannot be a duplicate as it was not part of the same gathering (Art. 8.2 of the ICN, McNeill & al. in Regnum Veg. 154. 2012). As a fruiting specimen is much better than a flowering specimen as the type of the name of a maple species, I designate here as lectotype of A. heptaphlebium the fruiting specimen cited above, i.e.: Tonkin: Tam-dao, prov. Vinh-yen, 29 Apr 1931, leg. Casalta, comm. Brillet, Herb. Forest. Tonkin 4 (P barcode P05212498). Murray (in Kalmia 8: 2–12. 1977) treated Acer heptaphlebium as a subspecies, A. campbellii Hook. f. & Thomson ex Hiern subsp. heptaphlebium (Gagnep.) A.E. Murray, while Van Gelderen (Maples World: 127. 1994) treated Acer heptaphlebium as a synonym of A. campbellii subsp. flabellatum (Rehder) A.E. Murray. I believe that A. heptaphlebium is a good species, and is distinct from A. campbellii by its larger samara (5.4–6 × 1.5–2 cm vs. 2.3–2.8 × ca. 0.8 cm), and leaf blade usually 5-lobed, rarely 3- or 7-lobed but the basal lobe very small, sinuses to ca. 3/4 width of blade (vs. usually 7-lobed, rarely 5- or 9-lobed, sinuses to ca. 1/2 width of blade). Gibbs & Chen (l.c.) noted that Acer heptaphlebium is possibly a threatened species. The name Acer taiwanense has not been adopted in works by any botanist since 1933, the time of its publication by Yamamoto (l.c.). In the type citation in the protologue, Yamamoto noted “Formosa, loco non indicato, 1 Aug. 1917” and “In Formosa endemica est.”, Formosa being the name for Taiwan at that time. After checking the type specimen at TAI, we found no collector or country information indicated, but only “Tam dao, 1 Aug. 1917” and the herbarium number “118952”. Fang (in Contr. Biol. Lab. Sci. Soc. China, Bot. Ser. 11: 246. 1939; in Fl. Reipubl. Popularis Sin. 46: 273. 1981) and Li (Woody Fl. Taiwan: 491. 1963) have pointed out that it was, in fact, collected by Hayata from Tonkin (Vietnam). “Tam Dao” is a locality in Vinh Phuc Province in northern Vietnam, which is one of the original localities from which A. heptaphlebium was collected. Since the specimen was found in the herbarium of Taiwan, it was easy for Yamamoto to infer that it was collected in Taiwan. Li & Lo (Fl. Taiwan, ed. 2, 3: 589–598. 1993) did not mention the name A. taiwanense and this name has never appeared in Vietnam floras (e.g., Hô, l.c.). After comparison with Acer specimens from Vietnam, the author found that A. taiwanense is the same species as A. heptaphlebium, characterized, as noted above, by its large samaras (ca. 6 × 2 cm) and shallowly lobed leaves. Since Acer taiwanense is an earlier validly published name, the name of this maple should be changed to A. taiwanense. Replacing the commonly used name A. heptaphlebium with one that has never been used since its publication would cause misunderstanding and confusion, particularly with its inappropriate epithet “taiwanense”. It seems better to conserve the name A. heptaphlebium (according to Art. 14 of the ICN) against A. taiwanense. Such conservation will prevent a disadvantageous nomenclatural change of an important species of maple widely distributed in Vietnam and Laos.