Nahuatlea obtusata (S.F. Blake) V.A.Funk, 2017

Funk, Vicki A., Sancho, Gisela & Roque, Nadia, 2017, Nahuatlea: a new genus of compositae (Gochnatieae) from North America, PhytoKeys 91, pp. 105-124 : 115-116

5. Nahuatlea obtusata (S.F. Blake) V.A.Funk comb. nov. Figs 3D , 7

Gochnatia obtusata S.F. Blake, Contributions from the United States National Herbarium 22: 652. 1924.

Type.

Mexico. Puebla: dry limestone hills at Tehuacan, 20 Dec 1895, C.G. Pringle 6253 (Holotype: US 00119530 [254705]; Isotypes: A 00008380, BM 000947903, BR 0000005318124, CM 2403, E 00413002, JE 00000693, K 000502539, GH 00008381, MEXU 01220107, MO 1544305, NDG 63791, NY 00169557, P 00703351, P 00703352, PH 00025961, S 10-11705, TEX 00000454, US 01100608). [ Cabrera (1971) mentions additional specimens at F, G, M, UC, and W but these were not found in JSTOR-GP.]

Description.

Shrub 1.0 –1.5(– 2.6) m tall; leaves coriaceous, (4.5)5-8(20) × 3-5 mm, broadly elliptic, apex rounded to obtuse, rounded at base, glabrous adaxially, cinereous-tomentose abaxially; heads short-pedunculate (ca. 2 mm long), in clusters of 10-20 heads, at apices of branches; involucre narrowly obconic, 6-8 mm tall × 2.8-3.2 mm wide, bracts in ca. 5 series, glabrous; flowers 5-6 per head; corollas white, 6.5-7.5 mm long; anther base caudate, tails ca. 2 mm long, fimbrillate; pappus 6.0-7.5 mm long, bristles biseriate, broadening slightly at the tips.

Jervis (1954) said that the leaf length is "rarely up to 2 cm" and the width is "less than 1 cm" and Cabrera (1971) lists the length as 4-20 × 3-13 mm. Both seem to be correct; we found only one specimen that had leaves 20 mm long and all but two were less than 1 cm.

Distribution.

Mexico: Puebla and Oaxaca.

Remarks.

Gochnatia obtusata was described by S. F. Blake (1924) and accepted as a good species by Jervis (1954). Cabrera placed it as a subspecies of G. hypoleuca as did Freire et al. (2002). The difference of opinion is based on the importance one gives to the characters that separate the two entities. Blake stated that G. hypoleuca could be separated from G. obtusata by the following characters: leaves chiefly elliptic, apex acute or acutish and mucronate, 20-50 mm × 8-15 mm; involucre 5-6 mm tall, phyllaries obtuse to acute or obtusely acuminate. We have added some additional characters: shrub or small tree 3-7 m; heads arranged in short clusters or panicles; involucre with bracts in 3-5 series; corolla 10-12 mm long; style branches 0.7-1 mm long; pappus up to 6.5 mm. In contrast, G. obtusata has the following: leaves broadly elliptic, apex broadly rounded to obtuse, not mucronate, 4.5-20 mm × 3-13 mm; involucre 6.5-7.5 mm tall, involucral bracts acute to sharply acuminate; style branches 0.5-0.7 mm long. Additional characters for G. obtusata include: shrub of 1.0-2.6 m; heads glomerate at tips of branches and in clusters of 1-several in the subterminal axils; involucre with bracts in 5-6 series; corollas 6.5-7.5 mm long; pappus up to 7.5 mm long. In the field the difference is striking with the larger more robust G. hypoleuca contrasting with the smaller, more compact G. obtusata . Therefore we have chosen to recognize G. obtusata as a separate species.

Figures

Figure 3. Images of four type specimens: A Nahuatlea arborescens (UC holotype) B N. smithii (K lectotype) C N. obtusata (US holotype) D N. hypoleuca (G holotype). [Furnished by the respective herbaria.]

Figure 7. Cabrera's drawing of Nahuatlea hypoleuca. A Habit B Head C Floret D Style E Anther F Pubescence. [Modified from Cabrera 1971.]