Ruellia scarlatina M.J. Silva, 2022

Silva, Marcos José Da, 2022, Ruellia scarlatina, a new name for the sixty-year-old but misunderstood Ruellia capitata Rizzini (Acanthaceae), Phytotaxa 547 (1), pp. 55-65 : 57-60

Ruellia scarlatina M.J. Silva , nom. nov. ( Figure 1 ).

= Ruellia capitata Rizzini (1956: 156 .) nom. illeg., non Ruellia capitata Buchanan-Hamilton ex D. Don. (1825: 120) .

Type:— BRAZIL. Goiás: Niquelândia, 26 July 1952, fl., localidade do Macedo, A. Macedo 3677 (holotype RB 78758 !; isotypes NY930506! S09-8233!, SP 84553!, US 2059785!, US 2197176!) .

Description:—Shrub or subshrub, erect, 0.7–1.8 m tall; stems subcylindrical at base and subquadrangular distally, green with brown spots, glabrous, few or non-branched on upper third; internodes 1.5–4.6 cm long, slightly dilated above the nodes. Leaves opposite decussate, membranaceous; petiole 6–7 mm long; leaf blade11–12 × 1.9–4.2 cm, narrowly elliptic, elliptic or oblong-elliptic, base attenuated, apex acuminate, margins entire, sparsely scabridulous with glandular-sessile trichomes on both surfaces, the scabridulous trichomes denser on the veins, adaxial surface dark green, abaxial surface opaque green, venation camptodromous-brochidodromous, secondary veins 8–10 per side, curved at apex, impressed on adaxial surface, prominent on abaxial surface, tertiary veins perpendicular to the secondary ones, impressed on both surfaces; cystoliths conspicuous on both surfaces. Thyrses glomeruliform, four-sided, 3–5 cm long, terminal, congested, sessile; bracts 3.9–5.5 × 0.4–0.6 cm, lanceolate, lance-elliptic, margins ciliate, apex acute, similar tonormal leaves in terms of indumentum, sessile; bracteoles 2.4–2.7 × 1.1–1.3 cm, widely ovate, pubescent and glandular-capitate on both surfaces, margins entire, apex acute, conspicuously nerved, sessile. Flowers 5.2–5.3 cm long; calyx 2.2–2.3 cm long, with glandular and pubescent trichomes on both surfaces, 5-lobed, lobes 2.2–2.5 × 0.49–0.51 cm, subequal, lanceolate, foliaceous, margins entire, apex obtuse; corolla 4.9–5 cm long, infundibuliform, scarlet-red, glandular-capitate externally, tube 2.6–2.7 cm long, the throat 2–2.3 cm long, subcylindrical, lobes 1.4–1.5 × 1–1.1 cm, slightly curved and spreading, ovate or ovate-elliptic, apex obtuse, rounded or emarginate; stamens 4, weakly didynamous, exserted, filaments inserted ca. 2.6 cm above the base of the corolla, sparsely hirsute-glandular, the shorter pair ca. 3.4 mm long, the longer pair ca. 3.5 mm long, anthers 5.8–6 mm long, dorsifixed, sagittate, mucronulate; ovary 4.2–4.3 × 1.3–1.7 mm, oblongoid or oblong-obovoid, densely and shortly hispid, styles 5.3–6.3 cm long, hispid, stigma bilobed, asymmetrical, nectar disc annular. Capsules 1.5–1.6 × ca. 0.5 cm, clavate, shortly acuminate, green when immature and cream-colored when mature, dense and short-tomentose; retinacula 2.9–3 mm long; calyx persistent and larger than the fruits. Seeds 7-8, 4.7–4.8 × ca. 4.8 mm, orbicular, light brown, apex obtuse, margins slightly whitish, with hygroscopic trichomes covering the entire surface.

Phenology:—Collected with flowers in June, and with flowers and fruits in August and September.

Distribution and ecology: —Endemic to Goiás State, Brazil, and collected so far in mountainous areas in the municipality of Niquelândia ( Figure 2 ). It grows in “cerrados densos”, “brejos”, edges of “florestas estacionais” or “florestas de galeria” on clayey and stony soils between 758 and 818 m. a.s.l.

Etymology:—The specific epithet “scarlatina” alludes to its scarlet-red corolla.

Additional specimens examined:— BRAZIL. Goiás: Niquelândia, ca. 2 km da estrada para Macêdo Velho, 14°21’03”S, 48°24’52’’W, 29 August 1995, fl., M. L. Fonseca, R. Marquete & F. C. A. Oliveira 431 ( IBGE, US); ibd., junto a cidade, Morro do Cristo , 14°27’08”S, 48°27’26’’W, 19 September 1996, fl. fr., 29 August 1995, fl., M. Aparecida da Silva & C.C. S. Ferreira 3145 ( US, IBGE); ibd., rodovia Niquelândia-Votoratim Metais (BR 535), cerca de 3, 4 km do trevo de Niquelândia , margens da rodovia, 14°26’08”S, 48°26’34.6”W, 818 m. a.s.l., 07 September 2013, fl., Pirani, J.R. et al. 6494 (K, RB, SPF, UB); ibd., 2.3 km N of Niquelândia on GO-535, in route to Macêdo Velho, measured from traffic circle leaving town, 14°42’02”S, 48°29’02”W, 20 August 2016, fl., fr., Erin Tripp & Nicolás Medina 5968 (NY, COLO); ibd., cerca de 3, 5 km antes de chegar a Vila Macedo, cerrado denso, 14°23’53”S, 48°25’58”W, 29 August 2019, fl., fr., M. J. Silva & A. A. Alonso 9887 (UFG); ibd., GO 535 em direção a Vila Macedo, cerca de 200 metros acima da bica, 14°27’03”S, 48°26’46”W, 758 m. a.s.l., 24 June 2021, fl., M. J. Silva & I. S. Santos 12860 (UFG), M. J. Silva & I. S. Santos 12861 (UFG), M. J. Silva & I. S. Santos 128602 (UFG), M. J. Silva & I. S. Santos 12863 (UFG) .

Preliminary conservation status:—Species classified as Critically Endangered (CR), Criterion B1 subcriteria v, vi., E vii, due to having an estimated Extent of Occurrence of 47,561 Km 2. It forms populations of less than 20 adults plants and grows in areas under strong anthropogenic pressure such as roadsides, but also in mountainous areas, inappropriate for agricultural practices or civil construction.

Morphological relationships and systematic position:— Ruellia scarlatina can be recognized by its subshrubby or shrubby habit, glabrous stems, glomeruliform and congested thyrses, with ovate or ovate-elliptic bracteoles, densely covered by glandular trichomes on both sides, flowers with calyx deeply divided into 5 lobes, corolla infundibuliform, scarlet-red, with external glandular trichomes and broad lobes, ovate or ovate-elliptic, stamens weakly didynamous, gynoecium shortly hispid, with clavate capsules with 7 or 8 orbicular seeds completely covered by hygroscopic hairs. According to Ezcurra (1993), due to its red corolla, Ruellia scarlatina could be included in the informal group Physiruellia, which, according to that author, is represented in South America by six species [ R. elegans Poiret (1816: 727) , R. reitzii Wasshausen & Smith (1969: 60) , R. brevifolia ( Pohl 1831: 155) Ezcurra (1989: 278) , R. angustiflora Ness (1847: 51) Lindau ex Rambo (1964: 23) , R. sanguinea Grisebach (1879: 260) and R. longipedunculata Lindau (1895:365) ].

Tripp (2007), in a phylogenetic study of Ruellia , recovered the species placed by Ezcurra (1993) into the informal group Physiruelliain the “Physiruellia clade”, which, according to that author, included plants generally with dichasia simple or compound, profusely branched, and often long-pedunculate, flowers subtended by paired bracteoles, corolla often inflated,ovary with 8-14 ovules,capsules clavate,and seeds with hydroscopic trichomes only on their margins. The species of this clade, according to that author, were previously placed in the sections Ruellia and Physiruellia by Lindau (1895).

Fernandes et al. (2020) cited six species of Ruellia with red flowers in Goiás State [ R. adenocalyx Lindau (1898: 46) , R. amplexicaulis ( Nees 1847: 59) Lindau (1895: 311) , R. angustior ( Nees1847: 34) Lindau (1898: 46) , R. brevifolia ( Pohl 1831: 84) Ezcurra (1989: 278) , R. densa ( Nees 1847: 47) Hieronymus (1878: 74) , and R. elegans Poiret (1816: 727) ]. Although R. scarlatina shares red flowers with them, it cannot easily be confused with any of them because of leaf peculiarities (shape, apex, aspects of the trichomes, venation pattern), the type of inflorescence, and capsules, and the number of seeds per capsule, as evidenced in the key below.

Figures

FIGURE 1. Ruellia scarlatina M.J. Silva. A. Flowering branch; B. Bracts; C. Detail of the cystoliths on adaxial surface of the bracts; D. Detail of the trichomes on abaxial surface of the bracts; E. Bracteole; F. Detail of the trichomes in inner surface of the bracteole. G. Detail of the trichomes in outer surface of the bracteole; H.Calyx opened out, note the lobes with unequal size; I. Detail of the trichomes in inner surface of the calyx; J. Detail of the trichomes in outer surface of the calyx; K. Corolla opened out; L. Detail of the trichomes in inner surface of the corolla; M. Detail of the trichomes in outer surface of the corolla; N. Pair of stamens, note the filaments sparsely hirsuteglandular; O. Anthers, left in frontal view; right in dorsal view, note the trichomes on the connective; P. Gynoecium; Q.Ovary detail, note the glandular disk and trichomes; R. Stigma detail; S. Capsules; T. Open capsule; U. Seed; V. Trichomes onthe surface of the seed. (Drawn by Cristiano Gualberto from M. J. Silva & I. S. Santos 12860).

FIGURE 2. Distribution of Ruellia scarlatina M.J. Silva. A. Map of Brazil, highlighting the state of Goiás in gray; B. Map of Goiás state, its limits and altitude variation; C. Municipality of Niquelândia, (dotted area) with the species distribution points. Abbreviations for states (BA, Bahia; GO, Goiás; MG, Minas Gerais; MS, Mato Grosso do Sul; MT, Mato Grosso; TO, Tocantins) and Federation unity (DF, Distrito Federal) of Brazil.