Chresta artemisiifolia Siniscalchi & Loeuille, 2019

Siniscalchi, Carolina M., Loeuille, Benoit, Filho, José Alves De Siqueira & Pirani, José R., 2019, Chresta artemisiifolia (Vernonieae, Asteraceae), a new endangered species from a recently created protected area in the Brazilian Caatinga, Phytotaxa 399 (2), pp. 119-126 : 120-124

Chresta artemisiifolia Siniscalchi & Loeuille , sp. nov. ( Figure 1 , 2 )

Species Chrestae martii similis, sed foliis laminis constrictis secus costas et nervos secundarios (non expansis), scapo breviore (5–11.5 cm, non 30–60 cm), syncephalo crescentia determinata (non indeterminata) et apice phyllariorum acuto (non obtuso) differt.

Type: — BRAZIL. Bahia, Sento Sé, Nascente na Grota dos Prazeres, no paredão rochoso, bioma Caatinga, fitofisionomia Savana Estépica, 437 m, 10º04’11.60” S, 41º37’27.60” W, 18 December 2015, J. A. Siqueira Filho., E.D. S. Almeida, E. M. B. Nunes, T. T. Bezerra & C. M. Siniscalchi 3671 (holotype HVASF!; isotypes to be distributed to RB!, SPF!, US!).

Description: —Perennial herb with a branched rootstock, ramified at the base, up to 0.5 m; stem 15–20 cm tall, striate, brownish-red, villose with simple minute hairs and glandular trichomes, glabrescent at the base. Leaves alternate, mostly concentrated at the apex of stems, simple, sessile or subsessile; overall contour of the leaves 1.4–8.2 × 0.6–3.2 cm, pinnatisect blade restricted to 0.1–0.3 cm around primary and secondary veins and sometimes tertiary veins, overall contour of the leaf ovate, greyish-green, villose with short-armed T-shaped hairs intermixed with abundant white glandular hairs on both sides, midrib prominent on both sides, venation pinnate, margins entire, apex acute, base attenuate. Synflorescence scapose, 5–11.5 cm long, scape villose with short-armed T-shaped hairs intermixed with abundant white glandular hairs, glabrescent in older synflorescences, light brownish-orange, engorged beneath the syncephalium, with evident striation. Syncephalia solitary, 1.2–1.8 cm tall, 0.8–1.5 cm diam., hemispherical, with capitula adpressed at base; secondary bracts 1.0–1.3 × 1 mm, subulate to ovate, villose with short-armed T-shaped hairs intermixed with abundant white glandular hairs. Capitula 9–30 per syncephalium, homogamous, discoid, sessile; involucre cylindrical; phyllaries 5- or 6-seriate, involucre 7–8 × 1.5–2 mm, outer phyllaries widely ovate, 0.8–1.6 × 0.6 mm, apex rounded, spinescent, completely villose or with indumentum concentrated on the upper half, glandular trichomes concentrated on the upper half of the blade, greenish-white on the center, purplish on the margins, margins membranaceous, mid phyllaries widely elliptical to obovate, 3.8–4.3 × 1–1.6 mm, apex rounded to widely acute, spinescent, pilose on the upper half of the blade, with white glandular trichomes, greenish-white on the center, purplish on the margins, margins membranaceous, inner phyllaries narrowly obovate to elliptical, 7–8.5 × 1–1.3 mm, apex acute to acuminate, spinescent, pilose on the upper half of the blade, with white glandular trichomes, greenish-white on the center, purplish on the margins, margins membranaceous; receptacle flat, glabrous, foveolate. Florets 6, bisexual, fertile; corollas actinomorphic, lilac, 5-lobed, tube 4.9–5.2 mm, throat 0.4–0.55 mm, with sparse glandular trichomes, lobes 2–2.5 × 0.3–0.4 mm, spreading, apex acute, with abundant globular glandular trichomes and simple unicellular trichomes at the apex, margins not thickened; apical anther appendages rounded, sagittate, cell walls not thickened, basal anther appendages calcarate, acute; style 10–11 mm, style shaft glabrous except for upper part right below arms, lilac trichomes, style base glabrous, lacking basal node, with nectariferous disc 0.4 mm long, style arms 3 mm long, pilose outside throughout, hairs acute, subulate. Pollen grains ca. 30 μm diam., oblate-spheroidal to spheroidal, echinolophate, Chresta - type II. Cypselae 2.0–2.2 × 0.6–0.8 mm, ca. 20-ribbed, turbinate, sericeous, brownish, twin-hairs with cells fused up to near to tip, with long digitiform glands on the junction between carpopodium and cypsela; carpopodium 0.1 mm long, 0.3 mm diam., conspicuous, ring-shaped, asymmetrical on the top, brownish-yellow, glandular on the apex, cell walls thickened; pappus triseriate, whitish to stramineous, straight, serrulate-setose, persistent, outer series 0.4–0.6 mm long, lanceolate, paleaceous, apex acuminate, median series 1.3–2.6 mm long, linear, paleaceous, apex long acuminate, inner series 4.9–6 mm long, lanceolate, paleaceous, apex rounded.

Distribution and habitat:— Chresta artemisiifolia is a rupicolous plant, growing over quartizitc rock outcrops or grottos, usually close to water sources or in places with intermittent water courses, at elevations between 400 and 600 m a.s.l., in the northwesternmost portion of Chapada Diamantina massif. Three of the known records are from within the proposed area of Boqueirão da Onça national park, along the border with the Environmental Protection Area, including the type specimen, and the remaining record is completely outside of the proposed protected areas ( Figure 3 ). At least in one of the known populations (Grota dos Prazeres) the new species grows sympatrically with Chresta martii , however, no intermediate individuals or signs of hybridization between the two species were found there.

Flowering and fruiting:— Flowering and fruiting specimens were collected in February, June, July and December, indicating a long flowering period not necessarily linked to the rainy season (October to April), as more usually seen with Caatinga plants.

Conservation status:— Chresta artemisiifolia has an extent of occurrence of 143.547 km 2 and area of occupancy of 15.977 km 2, indicating that the species is Endangered (EN) under subcriteria B1 and B2, with the additional factors that the species is found in less than 5 locations. Moreover, the know total population has less than 2,500 individuals, with each subpopulation presenting less than 100 individuals. Therefore, the proposed conservation status is EN B1a+2a; C2a(i).

Etymology:— The epithet artemisiifolia refers to the leaves with pinnatisect, constricted leaf blades that surround the venation, similar to the leaves of Artemisia Linnaeus (1753: 845) , Asteraceae ( Figure 2C, D ).

Additional specimens examined (paratypes):— BRAZIL. Bahia : Sento Sé, Parque Nacional do Boqueirão da Onça, Olho d’água, afloramento rochoso, 526.97 m, 10º10’27.19” S, 41º30’27.52” W, 1 February 2010, J.A. Siqueira Filho et al. 2343 (HVASF!); localidade Prazeres, região de água corrente na época chuvosa, 541 m, 10º10’21.22” S, 41º30’35.23” W, 19 July 2011, V.M. Cotarelli et al. 890 (HVASF!); Brejo da Brázida, Grota de Santana, 492 m, 10º16’37.40” S, 41º37’05.30” W, 13 June 2012, N.M.P. Braga & C.R.S. Oliveira 71 (HVASF!, SPF!).

Figures

FIGURE 1. Chresta artemisiifolia. A. Habit with synflorescences. B. Adaxial surface of leaf. C–D. Syncephalia. E. Floret with pappus. F–I. Phyllaries from most internal to most external. K–M: Pappus series, from most internal to most external. J. Cypsela.

FIGURE 2. Chresta artemisiifolia. A. Habit. B–C. Details of branches showing the leaves with constricted blades. D. Comparison between leaves of C. martii (left) and C. artemisiifolia (right). E–F. Syncephalia with open florets. G. Microscopic section showing the cells of the carpopodium wall, the glands above the carpopodium and the twin-hairs. H. Microscopic section showing the tips of the petals, with short, simple trichomes and globular glandular trichomes. A.–H. by C.M. Siniscalchi.

FIGURE 3. Known distribution of Chresta artemisiifolia in relation to the proposed area of the mosaic of conservation units in Boqueirão da Onça. The detail on the bottom left represents the distribution of C. harleyi, C. hatschbachii, C. martii and C. subverticillata in relation to C. artemisiifolia.