Xenophyllum esquilachense (Cuatrecasas) Funk (1997: 239)

Calvo, Joel, Muñoz-Schick, Mélica & Moreira-Muñoz, Andrés, 2018, Towards a better understanding of Xenophyllum esquilachense (Senecioneae, Compositae), a poorly known Andean species, Phytotaxa 382 (3), pp. 288-292 : 290-292

Xenophyllum esquilachense (Cuatrecasas) Funk (1997: 239) . Werneria esquilachensis Cuatrecasas (1956: 192) .

Type:— PERU. Puno: San Antonio de Esquilache, 12 May 1937, D. Stafford s.n. (holotype: K).

Senecio pfisteri Ricardi & Marticorena (1964: 25) . Type:— CHILE. Arica-Parinacota: depto. Arica, Portezuelo de Chapiquiña , faldeos al lado norte del campamento, 4400 m, 10 February 1964, C. Marticorena, O. Matthei & M. Quezada 116 (holotype: CONC-29863; isotype: CONC), syn. nov.

Perennial herb 5–10 cm tall, with erect or decumbent stems arising from a delicate, glabrous rhizome. Leaves 3-forked, abruptly narrowed into a pseudopetiole, 11.2–15.5 mm long, 3.3–4.6 mm wide at the maximum width point, scabrous-ciliate on the margin (cilia ca. 0.17 mm), somewhat fleshy, becoming entire the uppermost ones; leaf lobules 2.4–3.9 mm long, 0.7–1 mm wide, with 2–3 rough mucronate teeth up to 1.4 mm long. Capitulum disciform, solitary, terminal, sessile or subsessile; involucre 10.4–15.1 mm long, 6.5–7.4 mm wide; involucral bracts 8–12, 5.4–7.2 mm long, 1.3–2.5 mm wide at the base, obtuse to acute. Female florets ca. 10, peripheral, with a vestigial tube ca. 2.1 mm long or without corolla; bisexual florets ca. 15, 6–10.6 mm long, 5-lobed, usually purple-colored. Style branches truncate with a crown of sweeping-hairs. Achenes glabrous, mature ones not studied; pappus ca. 11.3 mm long, barbellate, whitish. Chromosome number: unknown. Figure 1 .

Iconography:— Ricardi & Marticorena (1964: 26, fig. 9).

Distribution and Habitat:— Bolivia (Oruro), Chile (Arica-Parinacota), and Peru (Moquegua, Puno). The species is also expected in the Peruvian department of Tacna, although no collections have been studied from that territory ( Fig. 2 ). Xenophyllum esquilachense grows in the subhumid and dry puna ecosystems, on steep volcanic slopes and sandy soils, usually protected by mats of other species or at the base of rocks, between elevations of 3700–4830 m. Some related species that were observed growing in the same habitat are, among others, Senecio trifurcifolius , Werneria orbignyana , Xenophyllum ciliolatum , Xenophyllum dactylophyllum , Xenophyllum juniperinum , Xenophyllum poposum , Xenophyllum staffordiae , and Xenophyllum weddellii .

Etymology:— The epithet refers to the Peruvian village of San Antonio de Esquilache (western Puno), where the type material was collected in 1937 by the English plant collector Miss Dora Stafford.

Phenology:— Flowering from February to April.

Discussion:— This species is well characterized by its leaves and disciform capitula. The leaves have a long pseudopetiole, and the lamina is 3-forked, each lobule usually having 2–3 rough mucronate teeth. The leaf margins are scabrous-ciliate. With regard to the capitulum, X. esquilachense is the only member of the genus with disciform capitula, which means that any confusion with the other species is unlikely. Each capitulum has ca. 10 female florets displaying a vestigial tube ca. 2.1 mm long or without corolla.

Cuatrecasas (1956) related this species to W. digitata Weddell (1856: 86) , later transferred by Funk (1997) to Xenophyllum , probably because the leaves of both species are 3-forked. However, in X. esquilachense each lobule has 2–3 rough mucronate teeth, whereas in X. digitatum the lobules are entire, rarely 2-forked. Moreover, the leaf indumentum is also different (scabrous-ciliate in X. esquilachense vs. glabrous in X. digitatum ). These species can also be easily differentiated by the type of capitulum, which is disciform in X. esquilachense and radiate with white ray florets in X. digitatum .

Ricardi & Marticorena (1964) published the unnecessary name S. pfisteri some years after the publication of W. esquilachensis . This species is well placed in the genus Xenophyllum due to the involucral bracts fused at the base, the absence of true supplementary bracts (calyculus), and the presence of leaves along the stems. Since the uppermost leaves usually become entire or subentire and reach the involucres, they might be confused as supplementary bracts as Ricardi & Marticorena (1964) did. Special attention has to be paid to this character for a proper identification, as well as to the reduced peripheral female tubular florets. As aforementioned, this latter character is unique within the genus. It is found in one species of the related genus Werneria , i.e., W. carnulosa Gray (1861: 140) , and in some Senecio species such as the members of S. sect. Metazanthus ( Meyen 1834: 356) Cabrera (1949: 78) and most species of S. sect. Oreophyton Cabrera (1949: 86) . For that reason, Ricardi & Marticorena (1964) probably tentatively placed their S. pfisteri within S. sect. Metazanthus . However, these species do not have the involucral bracts fused at the base and display genuine supplementary bracts, which are indeed characteristic characters of the genus Senecio .

Finally, it should be noted that the collector number of the holotype indicated in the protologue of S. pfisteri should be “116” instead of “207”. The collection Ricardi et al. 207 corresponds to a paratype.

Specimens examined:— BOLIVIA. Oruro: prov. Eduardo Avaroa, Challapata, comunidad Churacani , 18°55’S 66°40’W, 1 April 2018, M. Guzmán 124 ( LPB) ; Eduardo Avaroa, Challapata, cerro Toro Ichurata , en línea recta a 34.38 km al E, 18°57’S 66°27’W, 27 February 2016, F. Zenteno, L. Moya & D. Villalba 16745 ( LPB) . CHILE. Arica-Parinacota: quebrada Cataguanchuta , 18°14’S 69°31’W, 17 December 1988, E. Belmonte 88644 ( CONC) ; pasado azufrera Tacora , 17°42’S 69°49’W, 17 March 2015, A. Moreira-Muñoz & F. Luebert 2407 ( SGO) ; Portezuelo de Chapiquiña , 18°19’S 69°30’W, 26 March 1961, M. Ricardi, C. Marticorena & O. Matthei 207 ( CONC) . PERU. Arequipa: Chiguata, faldas del nevado Pichu Pichu , 16°27’S 71°27’W, 20 June 2004, V. Quipuscoa & al. 2949 ( HSP) ; Chiguata, ca. 2 km arriba del túnel del Simbral, carretera a Salinas , 16°22’S 71°17’W, 15 April 2018, V. Quipuscoa & M. Balvin 7541 ( HSP). Moquegua: General Sánchez Cerro, Yunga, Sura-Perusa, 16°11’S 70°38’W, 13 April 2012, D. Montesinos 3804 ( HSP) ; General Sánchez Cerro, Yunga, Perusa , 16°11’S 70°37’W, 3 March 2018, D. Montesinos & J. Calvo 5958 ( HSP) .

Key to the Xenophyllum species from southern Andes, i.e., S Peru, Bolivia, Chile, and Argentina (modified from Funk (1997))

1. Leaves forked, finger-like, or notched at the apex.............................................................................................................................2

– Leaves entire.......................................................................................................................................................................................3

2. Capitula disciform ..................................................................................................................................................... X. esquilachense

– Capitula radiate...................................................................................................................................................................................8

3. Ray florets not surpassing the involucre or barely so, yellowish.......................................................................................................4

– Ray florets conspicuously surpassing the involucre, whitish.............................................................................................................5

4. Leaves linear, (4.9–) 6.8–8.6 mm long, not adpressed to the stem .................................................................................. X. ciliolatum

– Leaves triangular, 5–7 mm long, adpressed to the stem ............................................................................................... X. juniperinum

5. Stems glabrous or glabrescent............................................................................................................................................................6

– Stems densely arachnoid....................................................................................................................................................................7

6. Leaves triangular, ciliate-denticulate at the upper half; involucral bracts 13–15............................................................ X. marcidum

– Leaves linear, glabrous; involucral bracts 8–12 ................................................................................................................ X. weddellii

7. Leaves articulated, with a long pseudopetiole...................................................................................................................... X. humile

– Leaves not articulated, slightly broadened at the base ...................................................................................................... X. poposum

8. Leaves notched at the apex.................................................................................................................................................................9 – Leaves forked or digit-like...............................................................................................................................................................10

9. Stem glabrous; leaves flattened in cross section, conduplicate, clearly broadened at the base .......................................... X. incisum

– Stem densely arachnoid; leaves terete in cross section, plane; barely broadened at the base........................................... X. poposum

10. Leaves digit-like...............................................................................................................................................................................11

– Leaves forked...................................................................................................................................................................................12

11. Subshrub up to 25 cm tall; capitula erect; ray florets conspicuously surpassing the involucre .............................. X. dactylophyllum

– Shrub 50–60 cm tall; capitula usually nodding; ray florets not surpassing the involucre.............................................. X. staffordiae

12. Leaves 2-forked .................................................................................................................................................................... X. rosenii

– Leaves 3-forked................................................................................................................................................................................13

13. Leaves forked nearly halfway; leaf lobules 2–4 mm long, linear, entire or 2–3-forked; involucral bracts 15–20 .......... X. digitatum

– Leaves shallowly forked; leaf lobules 1–2 mm long, triangular, entire; involucral bracts 13–14 ........................ X. pseudodigitatum

Figures

FIGURE 1. Xenophyllum esquilachense. A. Habit (Tacora, Chile; photo by A. Moreira-Muñoz). B. Detail of the capitulum (Tacora, Chile; photo by B. Knapton). C–D. Detail of the leaves (Perusa, Moquegua, Peru; photos by J. Calvo).

FIGURE 2. Distribution map of Xenophyllum esquilachense.