Lavoisiera minima A. B. Martins & Almeda, 2017

Martins, Angela B. & Almeda, Frank, 2017, A Monograph of the Brazilian endemic genus Lavoisiera (Melastomataceae: Microlicieae), Phytotaxa 315 (1), pp. 448-450 : 448-450

25. Lavoisiera minima A. B. Martins & Almeda , sp. nov.

Subshrubs 40–50 cm tall. Branches glabrous. Leaves sessile to subsessile, coriaceous, keeled, densely imbricate and congested at the ends of the brachlets, margins callose-thickened and shortly serrulate, 1-nerved. Flowers 6-merous, solitary. Hypanthium campanulate, glabrous. Petals pale pink. Ovary 2-locular, 1/2 inferior.

Type:— BRAZIL. Minas Gerais : “Estrada Diamantina-Curralinho (Extração) a 3 km de Diamantina ,” 19 June 1980, N. Menezes, J. Semir, J. R. Pirani, N. M. Castro and A. Furlan CFCR 195 (holotype: UEC!; isotypes: SPF, US!) .

Erect, rigid, dichotomously or fastigiately branched subshrubs 40–50 cm tall. Branches and branchlets rounded, furrowed longitudinally on alternate faces, defoliating and decorticating basally with age; internodes 1–2 mm long, glabrous, with knobby thickenings that persist at each point where a leaf has fallen away, nodes with conspicuous leaf scars and inconspicuous glandular trichomes. Leaves sessile to subsessile, spreading-ascending, densely imbricate and congested at the ends of the branchlets, concealing the upper internodes; blade 3.5–4 × 2.2–2.5 mm, rigid-coriaceous, ovate to oblong, base subrounded, apex mucronulate, margins broadly callose-thickened and shortly serrulate to serrulate-ciliate, eglandular, keeled abaxially, grayish-green (when dry), glabrous on both surfaces, 1-nerved, the midvein abaxially with short appressed serrulations at the tip. Flowers 6-merous, solitary, at first terminal on the branchlets but soon pseudolateral, commonly overtopped by the lateral branchlets, sessile to inconspicuously subsessile, subtended by 2–3 pairs of modified bracts. Bracts 3.5–4 × 3.8–4 mm, typically wider than mature cauline leaves, sessile to subsessile, petiole flattened 0.5 mm long, ovate to subrounded, base rounded to attenuate, apex mucronulate, margin callose-ciliate, the cilia 0.3 mm long, glabrous, 1-nerved to obscurely 3- nerved. Hypanthium (at anthesis) 2.5–3 × 3.5 mm, 4 mm wide distally, campanulate, glabrous. Calyx tube inconspicuous to ca. 0.5 mm long; calyx lobes (at anthesis) 2.3–3 × 1.5 mm, ovate-oblong, apex apiculate and slightly revolute, margin callose, ciliate and occasionally glandular, obscurely keeled, green to greenish-gray, membranaceous, glabrous on both surfaces, tardily caducous in post-anthesis. Petals 8–10 × 4–6 mm, reportedly pale pink, obovate, apex asymmetrically subrounded, base attenuate, margin minutely and inconspicuously glandular-ciliolate. Stamens 12, dimorphic: large (antesepalous) stamens 6, filaments 4–5 mm long, anther thecae 2–2.5 × 0.8 mm, oblong, yellow at anthesis (brownish-purple when dry), rostrum 0.6 mm long, white, pedoconnective 5–6 mm long, appendage 1–1.5 mm long, obscurely lobed, yellow; small (antepetalous) stamens 6, filament 3.5–4 mm long, anther thecae 1.8–2 × 0.8 mm long, oblong, rostrum ca. 0.6 mm long, white, pedoconnective 3–3.5 mm long, appendage 1 mm long, rounded, yellow. Ovary 2-locular, ca. 1/2 inferior, globose, style 5–6 mm long, slightly curved at the apex, glabrous, stigma punctiform. Fruiting hypanthium (including calyx lobes) 6–7 mm long. Capsule (at maturity) 3–4 mm long, globose, brown, enveloped by the persistent hypanthium, dehiscing from the base to the apex. Seeds 0.73–0.80 × 0.55–0.63 mm, somewhat bluntly angular-reniform, grayish-brown, periclinal cell walls of the testa faintly concave (foveolate) raphal zone about 35–45% the length of the seed. Chromosome number unknown.

128 • Phytotaxa 315 (1) © 2017 Magnolia Press

MARTINS & ALMEDA

Illustration:— Figure 48 .

Phenology:—The type and only known collection had flowers and old fruits in June.

Distribution and habitat:—Endemic to Minas Gerais, where it is known from campo rupestre in a small area of the Cadeia do Espinhaço near the town of Diamantina at 1100–1200 m elev. Figure 28 .

Conservation status:—Our attempts to relocate this species at the type locality were unsuccessful. We have no information on its abundance and distribution since no exact coordinates were included on the specimen label. Until it is recollected we prefer to assign it a Data Deficient (DD) status.

LAVOISIERA ( MELASTOMATACEAE )

Phytotaxa 315 (1) © 2017 Magnolia Press • 129

Discussion:—Although L. minima is known only from the type collection, it is readily recognized by its comparatively small rigid-coriaceous leaf blades that are spreading-ascending, densely imbricate and concealing the short upper internodes. The blades are prevailingly 1-nerved, conspicuously keeled abaxially, glabrous on both surfaces and the margins are broadly callose-thickened and short-serrulate to serrulate-ciliate. These characters together with its glabrous hypanthia, tardily caducous, ciliate calyx lobes, and 2-locular ovary make it unmistakable.

Lavoisiera minima is morphologically closest to and was likely derived from the widespread and variable L. imbricata ( Figure 43 ) which differs by its larger leaf blades (5–8 × 3–7.5 mm), longer petals (8–27 mm), shorter pedoconnective (2–3 mm) on the smaller set of stamens, persistent calyx lobes, and 6-locular ovary that is completely or at least 4/5 inferior. The only other species with which L. minima might be confused is the superficially similar L. tetragona ( Figure 63 ). The latter also has rigid-coriaceous keeled and imbricate leaf blades that conceal upper internodes but it is typically a decumbent shrub with 5-merous flowers, longer petals (5–20 mm), 5-locular ovaries, and persistent calyx lobes that lack the well-defined ciliate margins.

Etymology:—The epithet for this species, which is derived from the Latin word minimus, refers to the comparatively small dimensions of its leaf blades.

Figures

FIGURE 28. Distributions of Lavoisiera caryophyllea, L. chamaepitys, L. minima, L. senae, and L. vestita.

FIGURE 43. Lavoisiera imbricata. A. Habit. B. Abaxial leaf surface. C. Abaxial bract surface. D. Flower bud. E. Flower. F. Hypanthium, calyx lobes and bracts. G. Ovary cross-section. H. Petal with margin detail (lower right). I. Ventral view of antesepalous stamen. J. Ventral view of antepetalous stamen. K. Seed. (Based on: A–K, Almeda et al. 8401, CAS, UEC.)

FIGURE 48. Lavoisiera minima. A. Habit. B. Abaxial leaf surface. C. Adaxial leaf surface. D. Abaxial bract surface. E. Hypanthium and calyx lobes. F. Ovary cross-section. G. Petal with enlargement of margin (lower left). H. Lateral view of antesepalous stamen. I. Ventral view of antepetalous stamen. J. Seed. (Based on: A–J, Menezes et al. CFCR 195, UEC, US.).

FIGURE 63. Lavoisiera tetragona. A. Habit. B. Abaxial leaf surface. C. Abaxial bract surface. D. Flower. E. Hypanthium and calyx lobes with lobe margin detail (upper right) and enlarged detail of adaxial intercalycine sinus. F. Ovary cross-section. G. Petal with lateral margin detail (lower left). H. Ventral view of antesepalous stamen. I. Ventral view of antepetalous stamen. J. Seed. (Based on: A–J, Almeda et al. 7808, CAS, UEC.)