Xenophyllum rigidum (Kunth) V.A.Funk, Novon 7(3): 240. 1997.

Calvo, Joel & Moreira-Munoz, Andres, 2020, Taxonomic revision of the Andean genus Xenophyllum (Compositae, Senecioneae), PhytoKeys 158, pp. 1-106 : 1

6. Xenophyllum rigidum (Kunth) V.A.Funk, Novon 7(3): 240. 1997.

Werneria rigida Kunth, Nov. Gen. Sp. [ed. fol.] 4: 149. 1818. Type. Ecuador. ["in summis Andibus Quitensium" according to the ind. loc.], [without date], F.W.H.A. Humboldt & A.J.A. Bonpland s.n. (lectotype: Humboldt and Bonpland’s collection at P as the first-step lectotype, designated as “holotype” by Funk (1997a: 240); P-00320180 (digital image!) as the second-step lectotype, designated here; isolectotypes: B-W-16432-01-0 (digital image!), HAL-0113456 (digital image!), P-02088567 (digital image!), P-02088569 (digital image!), P-02088570 (digital image!)).

Oresigonia pycnophylla Willd. ex Rockh., Bot. Jahrb. Syst. 70: 292. 1939, nom. inval. pro syn. ( Turland et al. 2018, ICN Art. 36.1).

Description.

Suffruticose plant, forming mats or hummocks, with rhizome-like stems up to 16 cm long covered with matted lanate indumentum and leaf bases, rather erect, simple or branched from the base. Stems 2.5-4 cm tall (aerial part), lanate. Leaves stellate-imbricate, extending into a sheath-like base that bears long silky trichomes; leaf laminas 12.6-13.5 × 2.3-2.4 mm, linear, obtuse at the apex, entire, elliptical in cross section, glabrous, unconspicuously nerved above, 1-nerved beneath (only visible in the lower half), fleshy, drying coriaceous, rather matte, papillose. Capitula radiate, erect, sessile, completely enclosed among the leaves. Involucres 11.5-12.8 × 7.2-11.3 mm, cupuliform; involucral bracts ca. 13, 6.9-8.5 × 1.7-2 mm, rather acute at the apex, dark-purplish. Ray florets ca. 13; corollas 9.6-11 × 1.5-1.9 mm, 4 to 6-veined, subentire to 3-toothed at the apex, conspicuously surpassing the involucre, white. Disc florets 38 to 41; corollas 5.1-6.2 mm long, whitish, usually yellow-tipped; style branches truncate with a crown of sweeping trichomes or slightly penicillate, purplish. Achenes 2.9-3.8 × 1-1.1 mm, cylindrical, white-villous with trichomes ca. 1 mm long (ribs invisible); pappus 6.8-8.4 mm long, barbellate, whitish. Chromosome number unknown. Fig. 11 .

Additional iconography.

Funk (1997b: 33, fig. 3D).

Distribution and habitat.

Endemic to Ecuador ( Bolívar, Chimborazo, Cotopaxi, Napo, Pichincha, Tungurahua). It grows in rocky outcrops and on sandy soils, rather dry, around the upper limit of vegetation of the superparamo ecoregion, at elevations of (3500-)3900-5100 m (Fig. 12 ).

Phenology.

Flowering from April to November.

Etymology.

The epithet rigidum means stiff, inflexible and it describes the leaves of this species.

Notes.

Xenophyllum rigidum is readily distinguished by its tough, linear, and apically obtuse leaves, as well as by its white-villous achenes. The rhizome-like stems are very robust and covered with a matted lanate indumentum where the leaf bases are sunked in. Another characteristic feature of this species is that the capitula are completely enclosed among the leaves.

Xenophyllum rigidum is morphologically close to X. funkianum , X. crassum (S.F.Blake) V.A.Funk subsp. crassum (see comments under these taxa), and X. humile . From the latter species, it differs in having larger leaves (12.6-13.5 × 2.3-2.4 mm vs. 2.5-10.8 × 0.5-1.5 mm in X. humile ), longer involucral bracts (6.9-8.5 mm vs 3.1-6.1 mm in X. humile ), higher number of disc florets (38 to 41 vs. (8-)22 to 39 in X. humile ), and white-villous achenes (vs. glabrous in X. humile ).

The specimen B-W-16432-01-0 kept at the Willdenow Herbarium is considered part of the original material and designated as isolectotype. Willdenow received the specimen from Humboldt as stated by Schlechtendal on the blue label at the bottom of the sheet. Although unnumbered, it contains an individual identical to those from the lectotype. See Hind and Jeffrey (2001) for further details on Humboldt and Bonpland’s material in the Willdenow Herbarium.

Additional specimens examined.

Ecuador. Bolívar: volcán Chimborazo, W side of the mountain, ca. 4 km from the road Ambato-Guaranda, 1°28'S, 78°48'W, 14 Sep 1995, P. Sklenář & V. Kostečková 1274 (QCA); Chimborazo: southern slope of Mount Chimborazo, 1°29'S, 78°48'W, 18 Aug 1939, E. Asplund 8391 (CAS, US); comunidad de Ambrosio Lazo, sector Patococha-Loma Caparina, 1°44'S, 78°53'W, 5 Jun 2009, D. Cárate et al. 593 (QCA); rd. to el refugio, ca. 17 km from Ambato-Guaranda rd., 0.5 km from refugio Whymper, 1°28'S, 78°50'W, 21 Oct 1995, V.A. Funk 11422 (US); Mt. Chimborazo, along road toward los refugios del Chimborazo, near the end of the access road at the superparamo, near camping spaces, 1°28'S, 78°50'W, 20 Apr 2018, V.A. Funk & J.M. Bonifacino 14053 (US); cerca del refugio E. Whymper, lado SW del Chimborazo, 1°28'S, 78°50'W, 14 Oct 1980, S. Halloy B-182 (NY); Chimborazo, Nov 1864, J. Isern 83 (C, MA); E side of the Chimborazo volcano, top of the terminal moraine around a small glacial lake, 1°28'S, 78°46'W, 4 Jul 1997, P. Sklenář & V. Sklenářová 2228 (QCA, US); W side of the Chimborazo volcano, 1°28'S, 78°52'W, 5 Jul 1999, P. Sklenář 7538 (QCA); S side of Chimborazo volcano, 1°28'S, 78°51'W, 1 Nov 2006, P. Sklenář 9338 (QCA); Cotopaxi: around the Illiniza peaks, 4 mi. W of town of Magdalena, 0°39'S, 78°40'W, 2 Apr 1991, R. Bensman 358 (QCNE); paramo de Quispicacha, summit plateau of loma Pucyucuchu, 1°5'S, 78°50'W, 25 Oct 2006, P. Sklenář 9269 (QCA, QCNE); Iliniza, slope along the main pathway to the saddle, 0°39'S, 78°42'W, 5 Dec 2010, V. Zeisek 13161 (QCA); Napo: Antisana, Oct 1923, H.E. Anthony & G.H.H. Tate 316 (US); Mount Antisana, 17 Aug 1955, E. Asplund 17334 (NY); Antisana, 13 Aug 1979, J. Black 163 (AAU); Quijos, reserva ecológica Antisana, faldas SW del volcán Antisana, 0°29'S, 78°10'W, 28 Nov 1998, A. Freire & L. Haro 2953 (QCNE, US); on south side of western glacier Antisana, 19 Jul 1960, P.J. Grubb et al. 569 (NY); on boggy plain above hacienda Antisana, 8 Aug 1960, P.J. Grubb et al. 704 (K); lado WNW del Antisana, 0°28'S, 78°9'W, 3 Feb 1980, S. Halloy B-62 (LIL); paramo nordwestlich von Antisana, 27 Mar 1934, E. Heinrichs 652 (MA); Quijos, reserva ecológica Antisana, SW slopes of volcán Antisana, just 100 m below glacier, 0°29'S, 78°9'W, 28 Nov 1998, D. Neill et al. 11495 (QCNE); volcán Antisana, W side of the mountain, 0°30'S, 78°10'W, 21 Jul 1997, P. Sklenář & V. Sklenářová 2793 (QCA); Quijos, reserva ecológica Antisana, faldas occidentales del volcán Antisana, NE de laguna Santa Lucía, 0°28'S, 78°10'W, 1 Aug 1998, H. Vargas & E. Narváez 2113 (QCNE, US); Quijos, reserva ecológica Antisana, faldas SW del volcán Antisana, 0°30'S, 78°10'W, 28 Nov 1998, H. Vargas & E. Narváez 3103 (QCNE, US); Quijos, reserva ecológica Antisana, faldas SW del volcán Antisana, 0°30'S, 78°10'W, 28 Nov 1998, H. Vargas & E. Narváez 3117 (QCNE, US); Antisana, west side, Mar 1880, E. Whymper s.n. (BM); Pichincha: Mt. Antisana, 16 Jul 1939, E.K. Balls 7308 (K); Antisana, falda WSW, 14 Sep 1986, A. Ehrenburg 172 (QCA); faldas occidentales del volcán Antisana, 0°28'S, 78°12'W, 8 Mar 1984, L. Muñoz 365 (LOJA, QCA); Tungurahua: Mocha, ca. 2 km NW of the mountain Carihuairazo, 1°24'S, 78°47'W, 23 Apr 1995, J.L. Clark 725 (COL, QCNE).

Figures

Figure 11. Xenophyllum rigidum A habit B capitulum C adaxial leaf surface D ray floret (pappus removed) E detail of ray corolla apex F style of ray floret G disc floret (frontward bristles removed) H style of disc floret I stamen. All details drawn from Asplund 8391 (US) except for A (drawn from Grubb et al. 569, NY), C (drawn from Asplund 17334, NY), and G-I (drawn from Anthony & Tate 316, US). Illustration by Alice Tangerini.

Figure 12. Distribution map of Xenophyllum rigidum (left hand), X. crassum subsp. crassum (right hand, closed triangle), and X. crassum subsp. orientale (right hand, open circle).