Ruellia umbrosa M. J. Silva, 2022

Silva, Marcos José Da, 2022, Ruellia umbrosa (Ruellieae, Acanthaceae) a new and critically endagered species from Lowlands of the Goiás state, Brazil, Phytotaxa 544 (1), pp. 81-88 : 82-87

Ruellia umbrosa M. J. Silva , sp. nov. ( Figs 1 & 2 )

Type:— BRAZIL. Goiás: Niquelândia, Reserva Particular de Desenvolvimento Sustentável Legado Verdes do Cerrado , Núcleo Engenho , Área do Rio Traíras , Floresta Estacional , cerca de 120 metros a partir da entrada da trilha principal do rio Traíras , 14°36’44”S, 48°28’51’W, 626 m. a.s.l., 29 May 2021, fl., fl., M. J. Silva & F.D. Santos 12547 (holotype UFG!; isotypes CEN!, UB!) .

Diagnosis: — Subshrubs 25–90 cm tall; roots fibrous; stems subquadrangular, rooting at the lower nodes, with diminute subsessile glandular trichomes; leaf blade 7–12.5 × 3–5.2 cm, ovate, elliptic or combinations, base attenuated or asymmetrical, margin nonciliate, minutely papillose on the midrib, and with subsessile patelliform glandular trichomes on both surfaces; flowers solitary, pedicellate, without bractlets, calyx with 5 lobes equal or slightly subequal, corolla white or slightly mauve; capsules 11.9–12 mm, ellipsoid with glandular trichomes on upper third; seeds 8, 3.3–3.4 mm long, orbicular, with hygroscopic adpressed trichomes.

Description:— Subshrubs 25–80 cm tall, decumbent and prostrate; roots fibrous; stems subquadrangular, green, recovered by subsessile glandular trichomes orange or gold; internodes 4.2–8.2(13) cm long, nodes slightly dilated, rooting. Leaves opposite decussate, petiolate, membranaceous; petiole 5–10 mm long, green, pubescent; leaf blade 7.0–12.5 × 3.0– 5.2 cm, ovate, elliptical or combinations, base attenuated or asymmetrical, margin non-ciliate, apex acuminate, minutely papillose on the midrib and with subessile patelliform glandular trichomes on both surfaces, the trichomes more concentrated on the veins; adaxial surface dark green, abaxial surface opaque or vinaceous; venation brochidodromous, secondary veins 7–9 pairs, curved to apex, impresed on adaxial face, slightly prominent on abaxial surface, tertiary veins perpendicular to the secondary ones, impressed; cystoliths inconspicuous on both surfaces. Flowers 2.6–2.7 cm long, pedicelate, solitary in the axils of the upper leaves; bracts 11.8–12 × 2.9–3.0 mm, lanceolate, similar to the normal leaves but sessile and smaller; bractlets absent, pedicel 2.0– 2.1 mm long, cylindrical, with hyaline glandular trichomes; calyx 11.6–12 mm long, 5-lobed, with glandular trichomes externally and internally in the upper third of the lobes, lobes free almost to the base of the calyx, 10–10.2 × ca. 1.0 mm, equal or slightly subequal, linear, with trichomes, apex obtuse or rounded; corolla 2.0– 2.5 cm long, white, sometimes slighthly mauve, outer surface stipitate glandular, the basal tube 1.0– 1.1 cm long, the throat campanulate-obconic 1.0– 1.1 cm long, lobes 5.9–6.0 × 5.9–6.1 mm, patent or slighlty spreading, orbicular, apex obtuse or rounded; stamens 4, didynamous, included, filaments inserted ca. 1 cm above the base of the corolla, sparsely hirsute-glandular, the shorter pair 6.0– 6.1 mm long, the longer pair 9.4–9.5 mm long; anthers 2.2–2.3 mm long, dorsifixed, base sagittate, ellipsoid; ovary 2.9–3.0 × ca. 1.0 mm, oblongoid, glandular-capitate on the upper third, styles 16.9–17.0 mm long, pubescent, stigma bilobed, nectar disc annular. Capsules 11.9–12.0 × 4.8–4.9 mm, ellipsoid, shortly acuminate, green with upper third vinaceous when immature, yellowish-brown with reddish upper third when ripe, pubescent; placentas breaking away with the retinacula and the seeds from the dry mature capsule; retinacula 3.7–3.8 mm long; fruiting pedicel 2.9–3.0 mm long, calyx persistent with the lobes attached to the capsules. Seeds 8, 3.3–3.4 × ca. 3 mm, orbicular, light brown, margin slightly whitish, uniformly indumented, the trichomes mucilaginous when wet.

Distribution and habitat:—Species so far collected in the Legado Verdes do Cerrado Private Sustainable Development Reserve , municipality of Niquelândia, Goiás State, Brazil ( Figure 3 ). It grows in the understorey of seasonally dry or gallery forest of the “Córrego da Sociedade”, “Curral do Vaqueiro”, and “Rio Traíras” on dark clayey or sandy-clay soils rich in litter, at 628–657 m a.s.l.

Phenology:—Collected with flowers in May and with flowers and fruits in June.

Etymology:—The specific epithet “umbrosa” from Latin umbrosus , alluding to that the species grows in a shaded environment in a riparian forest.

Preliminary conservation status:— Ruellia umbrosa presented an Extent of Occurrence estimated at 33.961 km 2, which is why it was classified as Critically Endangered (CR) Criteria B1 subcriteria b(i, iv, v). It was collected in gallery forests, a very common vegetation type in the northern part of Goiás State, and future explorations may reveal new sites of occurrence.

Additional specimens examined (paratypes):— BRAZIL. Goiás: Niquelândia, Reserva Particular de Desenvolvimento Sustentável Legado Verdes do Cerrado, Núcleo Engenho , Área do Rio Traíras , Floresta Estacional , cerca de 120 metros a partir da entrada da trilha principal do rio Traíras , 14°36’44”S, 48°28’51’W, 626 m. a.s.l., 29 May l 2021, fl., M. J. Silva & F.D. Santos 12543 (UFG), 12544 (UFG), 12545 (UFG), 12546 (UFG); ibd., Floresta galeria, sobosque da vegetação, 14°36’42”S, 48°28’47’W, 628 m. a.s.l., 23 June l 2021, fl., fr., M. J. Silva & I. S. Santos 12758 (UFG), 12759 (UFG), 12760 (UFG), 12761 (UFG), 12762 (UFG), 12763 (UFG), 12764 (UFG), 12765 (UFG), 14°36’59”S, 48°25’05’W, 702 m. a.s.l., 24 June 2021, fl., M. J. Silva & I. S. Santos 12829 (UFG), 12830 (UFG); ibd., Área do Córrego da Sociedade Floresta estacional, cerca de 150 metros à partir do Córrego, 14°38’34”S, 48°28’34’W, 657 m. a.s.l., 23 June 2021, fl., fr. M. J. Silva & I.S. Santos 12698 (UFG), 12702 (UFG); ibd., Área do Curral do Vaqueiro , Altura do Córrego de mesmo nome, 14°41’31”S, 48°26’35’W, 747 m. a.s.l., 23 June 2021, fl., fr. Floresta Estacional, M. J. Silva & I. S. Santos 12876 (UFG), 12875 (UFG) .

Notes:— Ruellia umbrosa is an decumbent or prostrate plant, has stems rooting at the lower nodes, leaves with subsessile patelliform glandular trichomes on both surfaces, solitary flowers in the axils of adult leaves with white or slightly mauve corollas, the tube proportional in size to the throat, placenta separating from the capsules along with the seeds that are in number of eight, and lacks bracteoles. By possessing such characters this species could be positioned in the informal group Chiloblechum according to Ezcurra (1993), which together with the informal group Ebracteolate formed a maximally supported clade (100 Posterior Probalbility) designated by Tripp (2007) as “Ebracteolate clade”.

For Tripp (2007) the Ebracteolate clade is entirely neotropical, has species from annual to perennial, subshrubby or shrubby with a considerable variable floral morphology, flowers solitary or in inflorescences, pollinated by various pollinators, with regular or very zygomorphic calyx, in addition to capsules with 2-8 seeds with hygroscopic trichomes on the entire surface.

Among the Ruellia species in Brazil, R. umbrosa resembles R. erythropus and R. epallocaulos , both positioned by Ezcurra (1993), respectively, in the informal groups Chiloblechum and Hygrophyloidei. It shares with both the subshrubby habit, the stem rooting below the nodes, the solitary flowers in the axils of the upper leaves, and the capsules with eight or more hygroscopic seeds. However, R. umbrosa differs from R. erythropus and R. epallocaulos by several characters related to the stem and leaves, presence of pedicel, absence of bractlets, size of flowers, corolla color, ratio of tube length and throat of the corolla, aspect of the calyx and its trichomes, as well as bracts shape, capsules’ trichomes, and geographical distribution, as evidenced in Table 1 .

Figures

FIGURE 1. Ruellia umbrosa M.J. Silva.A. Habit; B. Cross section of the stem; C and D. Leaf shapes; E. Leaf base; F.Adaxial leaf surface showing the trichomes and aspect of margin; G. Abaxial leaf surface showing the trichomes; H. Flower bud; I. Flower in frontal view; J. Glandular trichomes in outer surface of the corolla; K. Calyx; L1. Inner surface of the calyx; L2. Glandular trichomes in outer surface of the calyx; M. Corolla opened outward; N. Portion of the androecium showing the point of union of the stamens. O. Trichomes of the filaments. P1. Anthers in frontal view. P2. Anthers in dorsal view. Q. Gynoecium; R. Trichomes of the styles. S. Detail of the stigma. T. Ovary and disk; U. Glandular trichomes at ovary apex; V1. Open capsule showing the seeds; V2. Apex the capsule showing the trichomes; X. Open capsule without seeds, schematic.; Z. Seed. (Drawings by Cristiano Gualberto, from the holotype).

FIGURE 2. Ruellia umbrosa M.J. Silva A. Habit, note the dark green leaves and calyx with equal lobes; B. Portion of the plant apex showing the paired flowers; C. Flower in frontal view, note the corolla whitish; D. Flower in frontal view, note the corolla slightly mauve; E. Capsules young, note the vinaceous color. Photographs by M.J. Silva from the holotype.

FIGURE 3. Distribution of Ruellia umbrosa M.J. Silva A. Map of Brazil, highlighting Goiás State in gray; B. Map of Goiás State, its limits, and altitudinal variations. C. Municipality of Niquelândia (dotted area) showing the species distribution points. Abbreviations for the states: BA, Bahia; GO, Goiás; MG, Minas Gerais; MS, Mato Grosso do Sul; MT, Mato Grosso; TO, Tocantins; and DF, Federal District of Brazil.