Lavoisiera rigida Cogniaux

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

33. Lavoisiera rigida Cogniaux in Martius (1883: 144). Type:— BRAZIL. Minas Gerais: “habitat in locis saxosis prov. Minas Geraes prope Diamantina ,” L. Riedel 1209 (holotype: LE!, photos, MICH!, NY!, RB!; isotypes: B, destroyed, BM!, C!, K!, M!, NY!, P!, US!, W!; photos of B isotype, F!, NY!).

Erect, rigidly and openly branched shrubs or small trees 1.5–3 m tall, the upper branchlets dichotomous, bark fissured on the lower trunk. Branches and branchlets rounded to subrounded, furrowed longitudinally on opposite faces, rigid, erect, glabrous, corky, defoliating and decorticating at the base with age, branchlets sometimes leafy to the base; internodes 2–3 mm long, with knobby thickenings that persist where a leaf has fallen away, nodes with conspicuous leaf scars and inconspicuous glandular trichomes. Leaves sessile to subsessile, antrorsely spreading to densely imbricate and concealing the internodes distally on the uppermost branchlets, petiole ca. 1 mm long, flattened, sometimes reddish; blade 18–20 × 8–12 mm, coriaceous, oblong-elliptic to ovoid-oblong, base attenuate, apex obtuse to obscurely rounded, margin callose-thickened, entire and minutely glutinous-verrucose, glabrous, somewhat viscid adaxially, randomly and sparingly glandular-punctate on both surfaces, grayish-green to yellowish-green, flat to subkeeled, faintly 3(–5)-nerved, only the midvein conspicuous, sometimes the leaves subtending the flowers becoming gradually wider but otherwise similar to the principal leaves. Bracts practically undifferentiated from principal leaves. Flowers (6–7–)9-merous, solitary, at first terminal but becoming central or pseudolateral with elongation of the lateral shoots, sessile. Hypanthium (at anthesis) 4–5 × 6–7 mm, broadly campanulate, glabrous, sparsely to moderately glandular-punctate and somewhat viscid. Calyx tube 0.2 mm long; calyx lobes (at anthesis) 1–1.5 × 2–3 mm, chartaceous, triangular-acute to cuspidate and sometimes terminating in a short glandular trichome, margins entire and shortly gland-edged, glabrous to glandular-punctate abaxially, glabrous adaxially, persistent. Petals 20–22 × 15–27 mm, pink-magenta with a white patch at the adaxial base, obovate to spatulate, apex asymmetrically truncate to shallowly emarginate with a terminal glandular trichome, base attenuate, margin entire, eciliate or with sessile glandular trichomes. Stamens (12–14–)16, dimorphic: large (antesepalous) stamens (6–7–)8, filaments 10 mm long, red, anther thecae 5 × 1.1 mm, yellow turning brown following pollination, oblong, rostrum 0.6 mm long, yellowish-white, pedoconnective 8 mm long, appendage 1–1.5 mm long, subquadrangular to obscurely bilobed, yellow; small (antepetalous) stamens (6–7–)8, filaments 8 mm long, red, anther thecae 5 × 1.1 mm, yellow turning bronze or red, rostrum ca. 0.5 mm long, pedoconnective 4 mm long, appendage ca. 0.5 mm long, subrounded, yellow. Ovary 8-locular, 2/3 inferior, style 9–10 mm long, glabrous, straight to slightly curved at the apex, white, stigma punctiform. Fruiting hypanthium (including calyx

LAVOISIERA ( MELASTOMATACEAE )

Phytotaxa 315 (1) © 2017 Magnolia Press • 151 lobes) 9–13 mm long, urceolate, constricted at the apex. Capsule (at maturity) ca. 10 mm long, enveloped by the persistent hypanthium and calyx lobes, dehiscing from the base to the apex. Seeds 1.03–1.29 × 0.47–0.56 mm, oblong to subreniform or ± L-shaped, dark grayish-brown, periclinal cell walls of the testa concave (foveolate), raphal zone about 70–75% the length of the seed. Chromosome number unknown.

Illustration:— Figure 56 .

Photographic images:— Figures 4J–L .

Phenology:—Flowering from November through April; fruiting specimens have been collected only in December and April.

Distribution and habitat:—Endemic to Minas Gerais where it is restricted to the Diamantina plateau of the Cadeia do Espinhaço in campo rupestre and sandy soils at 1035–1410 m. Figure 26 .

Conservation status:—This local endemic is known from 22 collections. At least one population is afforded some protection in Parque Estadual do Biribiri. The EOO is 268 km ² and the AOO is 28 km ². Habitat destruction does not appear to be a threat to existing populations but periodic fires pose an ongoing threat. We assign this species a classification of Endangered (EN): B2ab(iii).

Discussion:—As emphasized by its specific epithet, Lavoisiera rigida is a rigid, erect shrub ( Figure 4J ) with open dichotomous branching and leaves that are mostly 20 mm long or less, somewhat viscid adaxially, and sparingly glandular-punctate on both surfaces. To the naked eye the leaves superficially appear glabrous. The flowers are modally 8-merous (rarely 6–7-merous), the petals are pink-magenta with a white patch at the adaxial base. The calyx lobes, which are persistent in post-anthesis, are triangular-acute to cuspidate and sometimes terminate in a glandular trichome, and the ovary is 8-locular. Among congeners that share its habit, leaf shape and size, and persistent calyx lobes, L. rigida is most similar to L. crassifolia . This latter species differs in having 5–6- merous (rarely 7-merous) flowers, a 5–6-locular ovary, longer calyx lobes (3–6 mm), and pink (occasionally white) petals that lack a discrete horizontal patch or band of white or yellow at the adaxial base. Another feature that is present in L. crassifolia but lacking in L. rigida is the dense nodal trichomes that form a more or less flattened line at the adaxial base of each leaf blade.

Lavoisiera rigida typically has 8-merous flowers but the flowers on the type are mostly 6–7-merous with one flower that is 8-merous. Riedel’s handwritten notes on the holotype describe the flowers as 5–10-merous. We have been unable to verify Riedel’s observation based on our study of populations in the field and the several collections cited below.

Additional specimens examined:— MINAS GERAIS: Diamantina plateau, 11 km N of Guinda on the road to São João da Chapada, 18˚10.143’S, 43˚42.582’W, Almeda et al. 8937 (CAS!, COL!, NY!, UEC!); Mpio. Serro, 19 km S of the main plaza in Diamantina on the road to São Gonçalo do Rio das Pedras, 18˚21.565’S, 43˚21.565’W, Almeda et al. 9089 (BHCB!, CAS!, K!, NY!, RB!, UEC!); Mpio. Diamantina , 13 km S of the main plaza in Diamantina on the road to São Gonçalo do Rio das Pedras, 18˚18.884’S, 43˚33.072’W, Almeda et al. 9100 (CAS!, COL!, UEC!); Mpio. Diamantina . Near large rock outcrop on right-hand side of road from Diamantina to Mendanha at Km 585 and the Caminho dos Escravos, -18.21751, -43.59379, Almeda et al. 9544 (BHCB!, CAS!, K!, MO!, NY!, RB!, UEC!, US!); Mpio. Diamantina , 4 km W of Hwy MG 220 along the S side of road to Conselheiro Mata , -18.27630, -43.71281, Almeda et al. 9604 (BHCB!, CAS!, NY!, UEC!); Mpio. Diamantina , trail on property of Pousada Real (formerly Pousada Jardim da Serra) on a ridge just east of Diamantina off of Estrada do Cruzeiro Luminoso, -18.23582, -43.58082, Almeda et al. 9635 (BHCB!, CAS!, NY!, UEC!); Mpio. Diamantina, Parque Estadual do Biribiri, “Morro do Beija-flor”, 18°10’44.45”S, 43°36’5.6”W, Araújo et al. 333 (HUFU, online image!); Mpio. Diamantina, Alrededores de Diamantina, camino a Mendanha, 18°13'S, 43°35'W, Arbo et al. 5093 ( US!); Mpio. Diamantina, Diamantina para a Serra dos Cristais, Duarte 8766 (BR!, M!, NY!, RB!, US-2!); Mpio. Diamantina, Subida para o Cruzeiro, Duarte & G. M. Barroso 7856 (M!, NY!, RB!, US!); Mpio. Diamantina, W. A. Egler s.n. (RB!); Mpio. Diamantina, Serra dos Cristais, Glaziou 19266 (BR-3!, C!, K!, LE!, R!, US!); Mpio. Diamantina , ca. 4 km from Diamantina ; road from Diamantina NE to Mendanha, King & Bishop 8556 (UB!, US!); Mpio. Diamantina , estrada Diamantina-Mendanha, Leitão Filho et al. 27864 (HUFU!, UEC!); ca. 37 mi from Diamantina, Maguire et al. 44777 (NY!, UB!, US!); Mpio. Diamantina , estrada Diamantina-Couto Magalhães, MG 2, próximo ao Rio Jequitinhonha, Martinelli & G. Smith 6235 (RB!); Mpio. Diamantina, Arranca Rabo, Mello Barreto 9375 (F!); Mpio. Diamantina, Formação, Mello Barreto 9742 (BHCB ex BHMH!); Mpio. Datas, represa de mineração perto do trevo da cidade, Pirani et al. 5211 (SPF!, UEC!). Mpio. Diamantina, Riedel s.n. (LE!); Mpio. Diamantina , margem esquerda da estrada para Milho Verde, Sano et al. 722 (CAS!). MINAS GERAIS?: Riedel s.n. (W!).

152 • Phytotaxa 315 (1) © 2017 Magnolia Press

MARTINS & ALMEDA LAVOISIERA ( MELASTOMATACEAE )

Phytotaxa 315 (1) © 2017 Magnolia Press • 153

Figures

FIGURE 4. Images of Lavoisiera species. A−C. L. macrocarpa (Almeda et al. 9173). D. L. mucorifera (Almeda et al. 9607). E. L. pulchella (Almeda et al. 9830). F−G. L. pulcherrima (Almeda et al. 9666). H−I. L. punctata (Almeda 9709). J. L. rigida (Almeda et al. 9089). K. L. rigida (Almeda et al. 9604). L. L. rigida (Almeda et al. 9635). Image credits: A−L. Frank Almeda.

FIGURE 26. Distributions of Lavoisiera canastrensis, L. cogniauxana, L. crassifolia, L. pulchella, and L. rigida.

FIGURE 56. Lavoisiera rigida. A. Habit. B. Adaxial bract surface with enlarged detail (upper left). C. Flower. D. Hypanthium and calyx lobes with enlarged detail of intercalycine sinus (upper right). E. Ovary cross-section. F. Petal with enlarged detail of apex (above). G. Ventral view of antesepalous stamen. H. Ventral view of antepetalous stamen. I. Seed. (Based on: A–I, Leitão Filho et al. 27864, UEC.)