Stylotrichium hortensiae V. Amorim & Roque, 2017

Amorim, Vivian Oliveira & Roque, Nádia, 2017, Stylotrichium hortensiae (Asteraceae-Eupatorieae): A new species from Chapada Diamantina, Bahia, Brazil, Phytotaxa 308 (2), pp. 283-288 : 284-287

Stylotrichium hortensiae V. Amorim & Roque , sp. nov. ( Figs. 1–2 )

Type:— BRAZIL. Bahia : Ibicoara , Morro dos Brejões, 873 m elev., 13º20 ʹ 49.7 ʺ S, 41º11 ʹ 48.9 ʺ W, 15 September 2016, V. O. Amorim 380 (holotype ALCB!; isotypes HUEFS!, HUFU!, K!, MBM!, NY!, RB!, SPF!, US!)

Erect shrub 1.5–2 m tall;branches terete, striate,vernicose,sparsely setose,glabrescent.Branches, leaf blades, peduncles, involucral bracts and corolla with uniseriate tector trichomes, uniseriate glandular trichomes with multicellular heads and biseriate glandular trichomes with unicellular heads. Leaves alternate, spirally arranged, persistent at the apex of branches, petiole ca. 6 mm long.; laminae 3.5–8 × 1–3 cm, coriaceous, oblanceolate to oblong, apex acute to obtuse, upper half serrate on margins, revolute, base attenuate, adaxial surface sparsely pilose to glabrescent, abaxial surface tomentose, venation reticulodromous suprabasal, within 3-levels deep. Capitulescence corymbiform, 10–50 capitula; peduncles 5–12 mm long, reddish, tomentose; bracteoles (2), alternate, 2.1–3.6 mm long, linear to oblanceolate. Involucre 5–8 × 5–8 mm, campanulate, subimbricate; involucral bracts 20–30, 3-seriate, outer bracts 2–3 mm long, lanceolate, inner bracts 3.7–4.7 mm long, oblanceolate to elliptic, apex acute to acuminate, ciliate on margins, tomentose. Receptacle convex to conical, sparsely pilose, glabrescent, paleaceous, paleae 3–4, oblanceolate. Flowers 35–45; corolla 3–3.6 mm long, white, sparsely pilose; lobes triangular, biseriate glandular trichomes with unicellular head (external), papillose (internal); anther ca. 1 mm long, base truncate, anther collar cylindrical; anther connective appendage ca. 0.2 mm long, as long as wide, emarginated; style ca. 6.5 mm long, clavate, branches papillose, pubescent below bifurcation, not enlarged in base, stylopodium present. Cypselae 2.5–3 mm long, cylindrical to obconical, 5- ribbed, densely setose, base curvate, attenuate; carpopodium terete, symmetric, decurrent on base of ribs. Pappus 25 subpaleaceous bristles, 1–1.5 mm long, subequal, uniseriate, straw color and purplish towards the tip.

Distribution and habitat:— Stylotrichium hortensiae is known only from Ibicoara municipality, occurring in the rocky field vegetation (campo rupestre).

Phenology: — Flowering in September.

Etymology:—The specific epithet is given in honour of Prof. Hortensia Pousada Bautista, an expert on Asteraceae , for her contributions through Flora da Bahia and stimulating new generations of botanists.

Among the Stylotrichium species with pappus, S. hortensiae is recognized by laminae oblanceolate to oblong (3.5–8 vs. 0.4–2.9 cm long), greater number of flowers (35–45 vs. 20–25), anther connective appendage as long as wide (vs. wider), style ca. 6.5 mm long (vs. 3.9–5 mm long), and pappus 1–1.5 mm long (vs. 0.2–1 mm long).

Stylotrichium hortensiae and S. glomeratum are sympatric but can be distinguished by the branches indument (setose vs. scabrous), leaves margins (serrate vs. entire), capitulescence (corymbiform vs. umbelliform), and pappus (subpaleaceous vs. absent), respectively.

On the other hand, Stylotrichium corymbosum is morphologically similar to the new species due to the venation suprabasal, leaf blade oblanceolate, margins serrate and glabrescent above. However, S. hortensiae differs from this species by the branches setose (vs. tomentose), leaves 3.5–8 × 1–3 cm (vs. 0.6–1.5 × 0.35–1 cm), paleae receptacle 3–4 (vs. 1–2), flowers per head 35–45 (vs. 20–25), corolla 3–3.6 mm long (vs. 1.8–2.4 mm long), respectively.

Figures

FIGURE 1. Distribution of Stylotrichium species in Chapada Diamantina, Bahia, Brazil.

FIGURE 2. Stylotrichium hortensiae. A. Floriferous branch. B.Abaxial surface showing the venation reticulodromous. C. Leaf transverse section. D. Uniseriate tector trichome. E. Uniseriate glandular trichome with multicellular head. F. Biseriate glandular trichome with unicellular head. G. Capitulum. H. Receptacles convex pilose. I. Corolla. J. Stamen. K. Style. L. Cypselae with subpaleaceous pappus. Illustrations by N. Nascimento.