Vernonia confusa Redonda-Mart., Villaseñor & A. Campos, 2016

Redonda-Martínez, Rosario, Villaseñor, José Luis & Campos-Villanueva, Alvaro, 2016, A new species of Vernonia (Asteraceae, Vernonieae) from the state of Oaxaca, Mexico, Phytotaxa 282 (3), pp. 211-217 : 211-216

Vernonia confusa Redonda-Mart., Villaseñor & A. Campos , sp. nov. ( Figs. 1–2 )

Type: — MEXICO. Oaxaca: Distrito Miahuatlán, Mpio. San Jerónimo Coatlán, 38.6 km SO San Jerónimo Coatlán, brecha a Piedra Larga , 30 noviembre 1990, A. Campos 3468 (holotype MEXU! ; isotypes MEXU! , K! , US! ).

Perennial herbs or suffruticoses 0.4–1.0 m high. Stems glabrous, striate. Leaves alternate, petioles 3.0–8.0 mm in length, blades lanceolate, rarely elliptic–ovate, 6.0– 15 cm long, 1.0–2.2 (–5.0) cm wide; leaf adaxial surface pilose or glabrate, with multicellular uniseriate trichomes, with apical cell subulate and with scattered glands ( Fig. 3 , A); leaf abaxial surface with abundant lageniform trichomes and some simple trichomes ( Fig. 3 , B–C); base occasionally decurrent on petioles; apex acute–apiculate, margins serrate and revolute. Heads homogamous, long-pedunculate, peduncles (3.0–)4.5–12.0 cm, glabrous, with subulate–lanceolate bracteoles, 4.0–14.0 mm long; inflorescence corymbose lax, with 3– 10 heads, involucre campanulate to hemispheric, 1.2–1.8 cm long, 1.2–2.3 cm wide; 5–6-seriate, glabrescent. Phyllaries linear–lanceolate, glabrate, imbricate, apex mucronate. Florets 50–60 per head, purple, actinomorphic, corollas 9.0– 13.0 mm long, lobes 3.0–4.0 mm long, tube 6.0–9.0 mm long, with abundant glands at apex of lobes and spread on tube. Style branches long, acute and hairy, 2.0–3.0 mm long. Anthers 3.0–4.0 mm long, with glandular indumentum, apex acute, base sagitate. Cypselae with 8–10 ribs, 3.0–5.0 mm long, with a pilose–glandular indumentum ( Fig. 2 , D). Pappus persistent, 2-seriate, external series shorter, of capillary bristles, 1.0– 2.2 mm long, internal series longer, of capillary bristles, 6.0–8. 0 mm long. Pollen 25.0–35.0 μm in diameter, subechinolophate with a microperforated tectum ( Fig. 3 , E–F).

Distribution, habitat and phenology: — Vernonia confusa is known only from six collections in the State of Oaxaca, at the mountain cloud forest, Pinus forest and Pinus – Quercus forest, at elevations of 1260–1790 m. It grows in association with Pinus , Quercus and associated species of mountain cloud forest types. Flowering and fruiting from August to December.

Ethymology:—The name of this species refers to the group of characters that have allowed the new species to be confused with other vernonias that have lanceolate blades, such as V. greggii A. Gray (1882: 204) , or an 5–6-seriate involucre, a pilose–glandular indument of the cypsela, and the same geographic distribution as V. karvinskiana DC. (1836: 62) subsp. karvinskiana .

Discussion:—The new species is recognized as a member of the genus Vernonia s.str., which shares the corymbose inflorescences, the presence of glands at the tips of the lobes, the tube of the corolla and the cypselae, the lageniform trichomes on the abaxial surface of the leaves, the latter being characteristic of the North American species of the genus ( Faust & Jones 1973, Redonda-Martínez et al. 2012), and the type A pollen which is characteristic of Vernonia ( Keeley & Jones 1979, Robinson 1999).

Considering the infrageneric classification of Vernonia by Gleason (1906), this new taxon could be included in V. series Umbelliformes because it presents characters in common with the taxa here grouped, such as the perennial or sufruticose herbaceous habit, and the grouped heads in subumbellate inflorescences with a uniform peduncle length. It is important to point out that the leaves present an intraspecific variation, yet they are lanceolate in most specimens but having elliptic–ovate leaves (Campos 3266, 3280).

The new species is similar to Vernonia greggii but with the glabrous stems, both share the same shape of the leaf blades, and the campanulate to hemispheric involucre. It differs from V. greggii in the absence of T- shaped trichomes on both surfaces of the leaves, the lanceolate–oblong phyllaries in V. greggii , the higher number of series of the involucre (4-seriate in V. greggii vs. 5–6-seriate in V. confusa ), and the purple- brown pappus in V. greggii vs. the white pappus in V. confusa . The new taxon shares the presence of glands and multicellular uniseriate trichomes with V. karvinskiana subsp. karvinskiana on the adaxial surface of the leaves; yet the later shows a difference in the apical cell of trichomes, as it is subulate in V. confusa but acute in V. karvinskiana subsp. karvinskiana . Both species have lageniform trichomes on the abaxial surface, but in V. confusa simple trichomes also present ( Fig. 2 B ), whereas in V. karvisnkiana subsp. karvinskiana the indumentum is formed also by uniseriate multicellular trichomes with the apical cell subulate (long uniseriate trichomes of subtype b1; Redonda-Martinez et al. 2012) and glands. Both species have a 5–6-seriate involucre with lanceolate phyllaries, indumentum pilose–glandular on the cypselae and their inflorescences corymbose; yet in V. confusa the inflorescence is lax, formed by 3–10 heads, while in V. karvinskian a subsp. karvinskiana it is compact with 6–15 heads. These species also differ in the number of florets. Vernonia karvinskiana subsp. karvinskiana has 30–40 florets, while V. confusa has 50–60 florets. These characteristics, together with the others included in Table 1 , prove that the taxon described here is new to science.

Additional specimens examined:— MEXICO. Distrito Miahuatlán, Mpio. San Jerónimo Coatlán, 10.3 km NE de Piedra Larga , 15 diciembre 1987, A. Campos y R. Torres 816 ( MEXU) ; 41 km SO de San Jerónimo Coatlán, brecha a Progreso , 7 agosto 1990, A. Campos 3266 ( MEXU) ; 40 km SO de San Jerónimo Coatlán, brecha a Progreso , 7 agosto 1980, A. Campos 3280 ( MEXU) ; 10 km SO del campamento Santo Domingo , 27 octubre 1980, R. Hernández M. et al. 5244 ( ENCB, MEXU) ; 17 km NE de Piedra Larga, camino Piedra Larga–Miahuatlán , 22 noviembre 1982, E. Martínez S. et al. 2739 ( MEXU) .

The distribution map of the new species is presented on Fig. 4 .

Figures

FIGURE 1. Vernonia confusa Redonda-Mart., Villaseñor &A. Campos. A & B. Branches with inflorescences showing variation of leaves. C. Head. D. Floret. E. Androecium. F. Cypsela with pappus.

FIGURE 2. Holotype of Vernonia confusa, specimen housed at Herbario Nacional de Mexico (MEXU).

FIGURE 3. Trichome diversity and pollen type of Vernonia confusa. A. Trichome on abaxial surface of leaves, uniseriate, with apical cell subulate (ut). B & C. Trichomes on adaxial surface of leaves. B. Simple trichome (st). C. Lageniform trichome (lt). D. Indumentum of cypselae, pilose-glandular, with glands (g) and twin hairs (th). E & F. Pollen type A. E. Polar view. F. Equatorial view.

FIGURE 4. Distribution map of Vernonia confusa in the state of Oaxaca, México.