Acmella kalelii M.M. Campos, C.F. Hall & J.U.M. Santos, 2019

Campos, Markus M., Fernandes, Géssica E. A., Hall, Climbiê F. & Dos Santos, João U. M., 2019, A new species of jambú (Acmella, Heliantheae, Asteraceae) from Amazonia, Brazil, Phytotaxa 403 (2), pp. 137-141 : 139-141

Acmella kalelii M.M. Campos, C.F. Hall & J.U.M. Santos , sp. nov. ( Figs. 2−3 )

TYPE:— BRAZIL. Pará: Santarém, Alter do chão, jardim, 08 Julho 1982, Blanch, L.C. 117 (holotype INPA!).

Acmella kalelii is a decumbent herb with florets with 4 or 5 lobes in the same capitulum, 4 or 5 anthers in the same capitulum, cypselae with inflexed cilia, ray cypselae 3–4-costate, disk cypselae obovoid, both types with antrorse trichomes on the bristles. Herb 30 cm tall, erect to decumbent, branched; internodes 1.5–6.5 cm long, stems sparsely pilose. Leaves slightly discolored, opposite, petiole 1.0– 1.5 cm long, leaf blade 1.5–6.0 × 0.4–2.5 cm, oval to elliptical, adaxial surface glabrous to sparsely pilose, abaxial surface sparsely pilose, base attenuate, apex cuspidate, margin slightly serrate, venation brochidodromous, main veins 3. Capitulescence with solitary capitula, axillary and terminal. Capitula radiate, 0.3–0.8 × 0.4–0.7 cm, involucre conical, receptacle cylindrical, 3.0–6.0 mm wide; paleae ca. 3.0 × 1.0 mm, oblanceolate, cymbiform, apex rounded, glabrous on both surfaces, main vein 1; involucral bracts in 2 series, ca. 4.0 × 1.5 mm, first and second series ca. 2.0 mm long, elliptical, margin ciliate, base attenuate, membranaceous, apex acute, main veins 6, glabrous on both surfaces. Florets: ray florets 8, inconspicuous, corolla ca. 1.7–2.0 × 1.0 long, glabrous, limb obovate, man veins 2, lobes 2–3, ovary ca. 1.8 mm long, narrowly obovate, wall sparsely pilose, style ca. 1.8 mm long; disk florets 90–110, corolla 1.2–1.8 × 0.3–0.5 mm, lobes 4–5 in the same capitulum, deltoid, anthers 4–5 in the same capitulum, brown, ca. 0.5 mm long, connective appendix ovoid, base short-sagittate, filament ca. 0.2 mm long, ovary 1.5–1.7 mm long, obovoid, wall sparsely pilose, margin long ciliate, style ca. 1.5 mm long, sigmatic branches ca. 0.3 mm long, recurved, apex truncate, yellow. Cypselae dimorphic; ray cypselae ca. 2.0 × 0.8 mm, obovoid, 3–4-costate, wall glabrous to sparsely pilose, margin long ciliate, cilia inflexed; disk cypselae ca. 2.0 × 1.0 mm, obovoid to oblong, rarely 3-costate, wall sparsely pilose, margin long ciliate, cilia inflexed. Pappus 1.0 mm long, ray cypselae with 3–4 equal bristles with antrorse trichomes, disk cypselae with 2 equal bristles with antrorse trichomes.

Common names: —jambú.

Etymology:— Acmella kalelii honors the son of its discoverer, Kalel.

Observations:—Among the species studied that occur in Amazonia, Brazil, Acmella kalelii is similar to A. brachyglossa in the shape and size of the leaves and ray cypselae markedly prismatic and not dilated. However, it is easy to differentiate A. kalelii by its opposite leaves, disk florets with 4 and 5 lobes in the same capitulum, antrorse trichomes on the bristles of the pappus, disk cypselae obovoid or 3-costate, ray cypselae 3–4-costate, in the same capitulum, with a long-ciliate margin and inflexed cilia on all edges, as well as a pappus around 1.0 mm long (vs. decussate leaves, disk florets with only 5 lobes, absence of trichomes on the bristles of the pappus, cypselae that are only 3-costate with randomly oriented cilia, and only 2 edges, and a pappus up to 0.5 mm long).

Among all the species of the genus, A. kalelii is similar to A. radicans var. debilis , which occurs in Venezuela, Bolivia and Peru ( Jansen 1985). These taxa have a similar habit, leaf shape and leaf size, and share similar aspects of the cypselae. However, A. kalelii has yellow florets, 8 inconspicuous ray florets that are glabrous at the base, disk florets with 4 and 5 lobes in the same capitulum, ray cypselae 3–4-costate, disk cypselae obovoid and 3-costate in the same capitulum, and margin of the cypselae not dilated (vs. white florets, 5 to 7 conspicuous ray florets that are densely pilose at the base, with only 4 lobes, and ray cypselae only 3-costate with a dilated margin in A. radicans var. debilis ).

Since the species is only known from a single collection, it is considered critically endangered (CR: B1, B2) according to the IUCN criteria. It shares the common name jambú with three other species of the genus and is used in the local cuisine. These species exhibit anesthetic properties on the tongue and lips when consumed.

Figures

FIGURE 2. Acmella kalelii. a. habit; b. involucral bract; c. ray floret; d. palea; e. disk floret; f. anther; g. style and stigma; h. ray cypsela; i. disk cypsela.

FIGURE 3. Acmella kalelii. a–b. palea; c–d. disk floret; e. ray floret; f–g. disk florets with 4 and 5 lobes; h. anther; i. style and stigma; j. ray cypsela; k. disk cypsela.