Senecio bipinnatifidus

Calvo, Joel, 2021, On the original material of two austral American Senecio species (Compositae) collected during British naval expeditions in 1828, now located in the herbarium of Geneva, Candollea 76 (2), pp. 261-267 : 262-264

Beechey’s Expedition and Senecio bipinnatifidus

Captain Beechey’s Expedition in the Pacific and Bering Strait was undertaken in His Majesty’s Ship Blossom from 1825 to 1828. The expedition arrived at Rio de Janeiro on 4 July 1825 after leaving England, crossed the Magellan Strait towards the Chilean ports of Concepción and Valparaíso, and in November of the same year reached Easter Island (Rapa Nui). Early 1826 they were in the nowadays French Polynesia, arriving at Tahiti in March and at Hawaii in May. Then, they sailed into Kamchatka and crossed the Bering Strait sometime during July. In February 1827 they came back to Hawaii and headed again to Kamchatka and the Bering Strait. They left Port Clarence (now Alaska) in early September 1827 to Monterey (California, USA), San Blas (Nayarit, Mexico), and Acapulco (Guerrero, Mexico). In May 1828 they visited Coquimbo and Valparaíso once again, returned to Rio de Janeiro around August, and arrived in England in September of the same year ( HOOKER & ARNOTT, 1830: i, ii) .

The plants collected by George T. Lay and Alexander Collie and other officers during the expedition were treated by William J. Hooker and George A.W. Arnott (1799–1868) in The Botany of Captain Beechey’s Voyage published in ten parts between 1830 and 1841 (STAFLEU & COWAN, 1979). The plant material was deposited in Arnott’s herbarium, which was acquired by the University of Glasgow [GL] and is currently housed in E (STAFLEU & COWAN, 1979; based on a quote from Asa Gray). However, Hooker also owned a set, which seems to be in part at K and E. The dispersal and present whereabouts of Hooker’s set entails further uncertainties because Hooker also sent one lot of Beechey’s plants to London that was further divided between Robert Brown and Aylmer B. Lambert (information according to Hooker, who received such particulars through a Lambert letter addressed to him; see MILLER 1970: 514). Brown’s herbarium was split up after his death in 1876 and most of this material found its final destination at BM, K, and E. On the other hand, Lambert’s rich herbarium was shortly after his death divided into 317 lots and acquired at a public auction by 16 buyers ( MILLER, 1970). Beechey’s plants of Lambert were bought by Delessert, now at G. In this regard, LASÈGUE (1845), who was the last and the long-lasting curator of Delessert’s herbarium, mentioned “Elles font partie de l’herbier de M. Delessert, qui possède même quelques-uns des échantillons uniques [they are part of Mr. Delessert’s herbarium, and even some specimens are unique]”.

The type material of Senecio bipinnatifidus was collected in Coquimbo ( Chile). Although no date is indicated in the protologue, Beechey’s Expedition only visited this locality once during the outbound journey to Magellan Strait, in May 1828 as indicated above. Until now, the location of the original material of this species remained unknown, which contributed to keep this name neglected for years ( FREIRE, 2008; RODRÍGUEZ et al., 2018). In this line, the species was treated as dubious by the foremost specialist on Chilean Senecio ( CABRERA, 1949) . Nonetheless, and based on the brief Latin description provided in the protologue, Cabrera presumed a potential affinity with the species belonging to Senecio subsect. Disecti Cabrera (e.g. S. cerberoanus J. Rémy , S. elquiensis Cabrera , S. viscosissimus Colla ).

A Beechey’s specimen identified as Senecio bipinnatifidus , most probably in Hooker’s handwriting, was found in G. The locality is missing but the plant perfectly matches the original description of the species ( Fig. 1 ). It is therefore selected to serve as nomenclatural type, hence, the name is resurrected.

Senecio bipinnatifidus Hook. & Arn., Bot. Beechey Voy. 1: 32. 1830.

Lectotypus (designated here): CHILE: sine loco [Coquimbo], s.d. [V.1828], Beechey Exped. s.n. ( G [ G00432676 ]!) .

= Senecio elquiensis Cabrera in Lilloa 15: 416. 1949, syn. nov. Holotypus: CHILE. Coquimbo Region: Rivadavia, 800 m, 6.XI.1923, Werdermann 99 (SI [SI001011] image!; iso-: E [ E00251534 ] image!, G [ G00432675 ]!, GH [ GH00012126 ] image!, LIL [ LIL001824 ] image!, LP [LP000477] image!, MO-909953 image!, S-R-5694 image!, UC [UC238373] image!).

Notes. – As it is nearly impossible to know if Hooker used no other element when preparing the account of the new species, the specimen at G is designated as the lectotype of the name Senecio bipinnatifidus . Because of the pinnatisect, glandular-pubescent leaves, the long tomentose involucres, and the white-sericeous achenes, among other characters, I identify it as S. elquiensis [1949], a species described from the surroundings of Rivadavia (Elqui, Coquimbo Region). This name, widely accepted thus far ( CABRERA, 1949; FREIRE, 2008; RODRÍGUEZ et al., 2018), has to be treated as a later heterotypic synonym of the priority name S. bipinnatifidus [1830]; accordingly, the new synonymy is proposed above.

Senecio bipinnatifidus is characterized by the combination of the following characters: stems with scattered, short glandular trichomes, leaves bipinnatisect, glandular-pubescent, semiamplexicaul the upper ones, capitula radiate, involucral bracts with long tomentose indumentum on the abaxial surface, supplementary bracts linear, a half as long as the involucral bracts, achenes white-sericeous. As emphasized in the original description (“involucro tomentoso”), this species is easily recognizable by the c. 1.5 mm long trichomes covering the involucre, which let one separate it from the similar species S. hirsutulus Phil. and S. balsamicus Phil. Other species with long tomentose indumentum on the involucre and occurring in the same region are S. coquimbensis Phil. and S. pubescens Phil. Senecio bipinnatifidus differs from the former in leaf division (bipinnatisect vs. pinnatifid to pinnatipartite in S. coquimbensis ) and from the latter in stem indumentum (with scattered, short glandular trichomes vs. dense, long glandular-hirsute trichomes in S. pubescens ) and in having slightly shorter involucral bracts (6–8 mm vs. 8– 8.5 mm in S. pubescens ). Senecio bipinnatifidus has also been confused with S. chamomillifolius Phil. (see Werdermann 99), a species with very similar leaves. However, this latter species has rather glabrous involucres or with very short glandular-pubescent trichomes; it is known from lower latitudes in the Atacama Region.

Additional material examined. – CHILE. Coquimbo Region: La Serena,

Compañía Baja, 17–20.IX.1933, Looser 2837 (G).

Figures

Fig. 1.– Lectotype of Senecio bipinnatifidus Hook.& Arn. [G00432676; Conservatoire et Jardin botaniques de Genève]