Schwenckia aurantiaca Paucar & Stehmann, 2021

Paucar, Jenny Olga Arrea & Stehmann, João Renato, 2021, Schwenckia aurantiaca (Solanaceae), a new species from calcareous outcrops of northern Minas Gerais, Brazil, Phytotaxa 508 (2), pp. 166-174 : 167-172

Schwenckia aurantiaca Paucar & Stehmann , spec. nov.

Figures 1–4 .

Type: — BRAZIL. Minas Gerais: Município de Jaíba, Reserva Biológica Serra Azul, Furados , 15°12’32”S, 43°51’16”W, 480 m, 15 April 2019, fl., fr., J.O.A. Paucar & J.R. Stehmann 203 (holotype BHCB195125!, isotype RB!) .

Diagnosis: — Schwenckia aurantiaca is characterized by the short cylindrical corolla with five linear orange appendages and triangular inter-appendicular lobes, and by the presence of two fertile stamens and three shorter staminodes. It is morphologically similar to S. glabrata Kunth in Humbold et al. (1817: 374), which differs in having a corolla with only two developed appendages, obcordate inter-appendicular lobes, and staminodes subequal to the fertile stamens.

Annual herb, erect or ascending, up to 55 cm tall. Stem hollow, initially single, later with secondary branches arising from the basal nodes, green to olive-green, striated, puberulent at the base, distally glabrescent, pubescent with both eglandular and glandular trichomes, the eglandular trichomes antrorse, with 1–4 cells, the capitate-glandular trichomes with 1–3 cells. Leaves simple, alternate, those of the lower stem with blades 8–19.9 × 4–12 mm, elliptic, membranaceous, glabrous to glabrescent on both sides, abaxially sparsely pubescent along the midrib with antrorse eglandular trichomes, the base rounded, the apex mucronate, the venation brochidodromous, with up to 3 pairs of primary veins, the petioles 3–8.8 mm long, glabrescent, with eglandular trichomes; leaves of upper stems usually longer and narrowed, with blades 14.6–34.8 × 2–10.5 mm, lanceolate to oblong-lanceolate, sparsely puberulent on both faces with 1–4 celled, eglandular trichomes and minute, two-celled, glandular trichomes, abaxially the midrib marked, the base attenuate, the apex acute, the margin entire or slightly wavy, sparsely ciliate with 4-celled, eglandular trichomes, the venation brochidodromous, with up to 6 pairs of lateral veins, petioles 1–5.6 mm long. Inflorescences paniculate, with at least 3 flowers simultaneously opened in anthesis, distributed evenly along the branches, axis glabrous, the bracts 0.9–1.3 mm long, lanceolate, ciliate-pubescent with 1–3 celled, eglandular trichomes, the pedicels 0.6–1.6 mm long, glabrous. Calyx in anthesis tubular, the tube 1.9–3.1 mm long, the lobes 0.5–1.5 mm long, unequal, the apex acute, papillose, the abaxial and adaxial surfaces glabrescent with sparse 1–3 celled glandular trichomes. Corolla cylindrical, glabrous, the tube straight, 7.5–10.3 mm long, greenish-yellow, purple on the upper third, the five corolla lobes each with one central appendage and two lateral lobes, the appendages linear, 1–2.2 mm long, unequal, one visibly smaller, green in pre-anthesis, changing to orange at anthesis, the inter-appendicular lobes unequal, 0.3–0.7 mm long, triangular, reflexed, papillose at the margin. Androecium with 2 fertile stamens, the anthers 0.7–1.1 mm long, connivent, the filaments free, 3.2–5.2 mm long, adnate in the lower third of the corolla tube, pilose at the base with mostly 4-celled (a few 5-celled), eglandular trichomes, the staminodes 3, 0.6–1.6 mm long, unequal, lanceolate to subulate, pilose with trichomes like those of the fertile stamens. Nectariferous disk present. Ovary 2-locular, 0.7–1.1 × 0.4–0.6 mm, subglobose, the style 5.9–7.5 mm long, the stigma capitate. Calyx persistent in fruit, tearing to the base. Fruiting pedicel up to 3 mm long. Capsule 2.6–3.8 × 2.1–3.6 mm, subglobose. Seeds 5–14, 0.7–1.4 × 0.6–0.8 mm, cuboidal to polyhedric, testa reticulate-foveolate. Chromosome number: unknown.

Distribution, habitat, and ecology:— Schwenckia aurantiaca has a restricted distribution, known only from an unusual ecosystem regionally called Furados, at Serra Azul Biological Reserve in the northern Minas Gerais ( Fig. 4 ). The typical vegetation is the arboreal Caatinga where Cavanillesia umbellata Ruiz & Pavón (1798: 166) (Malvaceae) is commonly found, with islands of calcareous outcrops, open areas with exposed rocks, and depressions that are seasonally flooded during the rainy season ( Fig. 4B–C ). This seasonally dry vegetation is adapted to the semi-arid climate of the region, classified as Aw-tropical with dry winter ( Reboita et al. 2015). The temporarily flooded, open areas are the habitat of the new species, which is an annual plant. The seeds germinate in the rainy season, which is when the plant grows, reproduces, and dies, leaving seeds in the soil to germinate in the next rainy season. Anthesis observed in cultivation, is nocturnal and has a cycle that begins with the opening of the corolla lobes in the late afternoon or early evening and closing at dawn the next day, a process repeated for three consecutive days. The tubular corolla, the nocturnal anthesis, and the sweet fragrance released at night suggest that moths may be the pollinators of S. aurantiaca .

Etymology: —The specific epithet “ aurantiaca ” comes from Latin and means orange, an allusion to the color of the corolla appendages during anthesis.

Phenology: —Flowering and fruiting occur from February to April.

Conservation status: —Critically Endangered (CR) [B1, B2b(i,iii), D]. Schwenckia aurantiaca is known only from one area of Serra Azul Biological Reserve, with one or few populations (<5), which are usually formed by numerous individuals (<50). The Serra Azul Biological Reserve has about 38 km 2 and was created to protect the unique environment known as Furados, which is strongly threatened by the surrounding intensive agricultural use (irrigated fruit farming) ( Barbosa & Santos 2008) and by fire, already documented for the area ( Fig. 4C ). In this environment, placed in the São Francisco river basin ( Fig. 4A ), the species is found only in open temporarily flooded places, which correspond to an area of less than 1 km 2 (AOO). Considering the specialized and restricted environment in which the species occurs, as well as the anthropic pressure on the Biological Reserve, our preliminary assessment for S. aurantiaca is Critically Endangered ( IUCN 2020).

Paratypes: — BRAZIL. Minas Gerais: Municipality of Jaíba, Reserva Biológica Serra Azul, Furados , 15°12’26”S, 43°51’17”W, 480 m, 20 February 2017, fl., fr., J. R. Stehmann et al. 6406 (BHCB186348); Reserva Biológica Serra Azul, Furados, 15°12’26”S, 43°51’17”W, 480 m, 20 February 2017, fl., fr., J. R. Stehmann et al. 6444 (BHCB190182) .

Figures

FIGURE 1. Schwenckia aurantiaca (A) habit, (B) flower with open corolla at night, (C–D) immature and mature capsule, (E–G) color change of the appendages, green in pre-anthesis (E), orange in anthesis (G).

FIGURE 2. Schwenckia aurantiaca (A) habit, (B) basal leaf, (C) upper leaf, (D) opened corolla tube with two stamens and three staminodes, all filaments pilose, (E) gynoecium, (F) opened calyx, showing lobes unequal in size, (G) corolla (in frontal view during anthesis) with the patent linear appendages (a) and the triangular papillose inter-appendicular lobes (ial), (H–I) reticulate-foveolate seeds. (A–I based on Paucar & Stehmann 203)

FIGURE 3. Holotype of Schwenckia aurantiaca (J.O.A. Paucar & J.R. Stehmann 203, BHCB).

FIGURE 4. Schwenckia aurantiaca distribution and habitat. (A) Map showing Furados (triangle), the site of the species occurrence in northern Minas Gerais, (B) Caatinga seasonally flooded during the wet season, with a view of the calcareous outcrops, (C) Caatinga with Cavanillesia umbellata Ruiz & Pavón in the Serra Azul Biological Reserve, disturbed by fire during the dry season in 2007. Photographs by J.R Stehmann.