Lavoisiera bradeana Barreto (1936: 70)

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

6. Lavoisiera bradeana Barreto (1936: 70) . Type :— BRAZIL. Minas Gerais: “Habitat in civitate Minas Geraes ad Curralinho prope Diamantina ,” 14 April 1892, A. F. M. Glaziou 19252 (holotype: R-9374!; isotypes: BR!, C!, F!- frag. ex P, K!) .

Erect, open laxly branched subshrubs 0.5–1 m tall. Branches and branchlets subrounded, slightly furrowed longitudinally on opposite faces, glabrous, defoliating at the base, distally subquadrangular, flushed with red; internodes 1–4 mm long with knobby thickenings that persist where a leaf has fallen away, nodes with short, vinaceous, glandular trichomes. Leaves sessile, semi-amplexicaul, densely imbricate and congested at the ends of the branchlets, less congested and spreading basally; blade 4–7 × 3–7 mm, coriaceous, rigid, ovate-oblong to ovate-suborbicular, keeled, base rounded, apex obtuse and shortly mucronulate, margin narrowly callose-thickened or not, uniformly serrulate or ciliate-serrulate, the marginal trichomes ca. 0.1 mm long, frequently glandular, yellowish to reddish, commonly viscous, sparsely (on distal adaxial surface) to copiously (on abaxial surface) glandular-punctate or beset with glandular appressed trichomes, the glands caducous, faintly 3–5-nerved, only the central vein elevated and conspicuous. Flowers (5–)6-merous, solitary, terminal but becoming pseudolateral or central with the elongation of lateral shoots, sessile. Bracts subtending the flowers several, subsessile, petiole ca. 1 mm long, blade 6–8 × 6–8 mm, ovate, base rounded, apex subacute, margins glandular-ciliate, similar to the principal leaves but typically wider when subtending fruiting hypanthia, 7–9-nerved, the marginal cilia up to 0.3 mm long. Hypanthium (at anthesis) 3–4 × 1.5–2 mm, broadly campanulate, 4–5 mm wide at the apex, constricted distally above the ovary, densely viscous at the base with a band of gland-tipped trichomes distally just below the

LAVOISIERA ( MELASTOMATACEAE )

Phytotaxa 315 (1) © 2017 Magnolia Press • 57 torus or at the middle, glabrous at the apex and internally. Calyx tube up to 2 mm long; calyx lobes (at anthesis) 5–7 × 1.5–2.5 mm, membranaceous, narrowly oblong to obscurely subspatulate, apex acute and glandular-mucronulate, margins subcallose, ciliate or glandular-ciliate, viscid or only vaguely so on both surfaces, tardily caducous, green. Petals 10–17 × 7–10 mm, reportedly pink to lavender-pink, obovate, apex asymmetrically truncate and apiculate, base attenuate, margin minutely glandular-ciliolate. Stamens 12, dimorphic: large (antesepalous) stamens 6, filaments 8–10 mm long, anther thecae 2.5 × 1 mm, yellow to purple-brown following pollination, oblong, rostrum ca. 0.5 mm long, yellow, pedoconnective 5–6 mm long, appendage 1–1.5 mm, bluntly rounded, yellow; small (antepetalous) stamens 6, filaments 6–9 mm long, anther thecae 1.5–2 × 0.5 mm, yellow, oblong, rostrum ca. 0.4 mm long, pedoconnective 1.5 mm long, appendage 0.3 mm long, blunt or rounded, yellow. Ovary 4-locular, 4/5 inferior, style ca. 0.7 mm long, glabrous, stigma punctiform. Fruiting hypanthium (including calyx lobes) 6–7 × 4 mm, oblong. Capsule (at maturity) 6 mm long, globose, enveloped by the persisting hypanthium, dehiscing from the base to the apex. Seeds 0.68–0.94 × 0.46–0.50 mm, oblong to oblong-arcuate, slightly keeled, reddish-brown, periclinal cell walls of the testa concave (foveolate), the raphal zone about 60% the length of the seed. Chromosome number unknown.

Illustration:— Figure 24 .

Photographic image:— Figure 1G .

Phenology:—Flowering January through March, and September through November; fruiting January, September and November.

Distribution and habitat:—Endemic to the Diamantina region and Serra do Cipó of the Cadeia do Espinhaço in Minas Gerais where it is local and uncommon to locally common among rocks and sandy soil in campo rupestre at 1060–1200 m. elev. Figure 20 .

Conservation status:—This species is known to us from 10 collections, four of which were collected in the course of our field work for this study. At least one population of this species is afforded some protection in Parque Estadual do Biribiri. The EOO is 953 km ² and the AOO is 16 km ². Fires are the major threat to the campo rupestre habitats of this species. Based on its limited range and narrow elevational distribution we recommend a classification of Endangered (EN): B2ab(iii).

Discussion —The distinctive features of L. bradeana include a 6-merous flower, 4-locular ovary, and relatively small keeled leaves that are uniformly viscous glandular-punctate on the abaxial surface. In older leaves of some specimens the sessile glands are caducous and their bases persist and lengthen into elongate rod-like epidermal thickenings reminiscent of cystoliths ( Figures 24B, C ). We have not seen this kind of indumentum and attendant epidermal modification in any other species of Lavoisiera .

The consistent 6-merous flower and 4-locular ovary of L. bradeana are character states shared only with L. humilis and some populations of L. scaberula . The former differs most conspicuously in its complete glabrosity and pronounced dimorphism of juvenile versus mature leaf blades. Lavoisiera bradeana also resembles L. scaberula , the species to which Mello Barreto compared it in the protologue. The latter is readily distinguished by the well-developed indumentum of gland-tipped hairs on cauline internodes and abaxial foliar surfaces, lack of a prominent abaxial keel-like midvein on mature leaf blades and lack of callose-thickened leaf margins. In the protologue, Mello Barreto also noted that L. bradeana is closely related to L. caparaoensis based on foliar and calyx lobe details. Lavoisiera caparaoensis , which is here regarded as an extreme geographic variant of L. imbricata , does resemble L. bradeana in having glabrous internodes and leaf blades that lack a callose-thickened margin. Its leaves, however, are attenuate at the base (vs. rounded), glandular-ciliate and essentially glabrous on both surfaces, and its ovary is consistently 6-locular (vs. 4-locular). The abaxial foliar surface of the “caparaoensis ” population also exhibits a faint hint of glandular punctations on abaxial foliar surfaces but they are not well-developed, exhibit no regular pattern, and never exude the copious viscosity typical of L. bradeana .

Romero et al. 5390, which was collected about 4 km from the city of Gouveia along the Diamantina-Gouveia road in Minas Gerais, is very much like L. bradeana in vegetative and indumentum details on abaxial leaf surfaces but it has 6-merous flowers and a 6-locular ovary like L. imbricata . We strongly suspect that this anomalous collection is a natural hybrid. Additional field study is needed to further evaluate its status because both of these species have been observed growing together in the Diamantina region.

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MARTINS & ALMEDA LAVOISIERA ( MELASTOMATACEAE )

Phytotaxa 315 (1) © 2017 Magnolia Press • 59

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. 8939 (CAS!, NY!, 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. 9097 (CAS!, 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. 9101 (CAS!, CESJ, COL!, HUFU, MICH!, MO!, NY!, UEC!); Mpio. Santana do Riacho, Serra do Cipó, ca. 8 km beyond church in Santana do Riacho on road to Lapinha and Pico do Breu, -19°.11490’, -43°.69937’, Almeda et al. 9718 (BHCB!, CAS!, K!, NY!, RB!, UEC!); Mpio. Diamantina , 6 km N of Diamantina , camino a Biribiri, 18°11'S, 43°36'W, Arbo et al. 5048 (SPF!, US!); Rod. BR 259, Raiz (Mpio. Datas), Hatschbach et al. 69710 (MBM!); Serra do Espinhaço, at Lapinha, ca. 20 km N of Serro, on road MG 2 to Diamantina, Irwin et al. 20850 (CAS!, UEC!); Mpio. Diamantina, Sentinella, Mello Barreto 9537 (BHCB, CESJ, F!, HUFU, NY!, RB!, SPF, UPCB); Mpio. Diamantina, Sentinella, Mello Barreto 9587 (BHCB ex BHMH!, F!, NY, UPCB); Mpio. Diamantina, Romariz 209 (RB!).

Probable hybrid between L. bradeana and L. imbricata :— MINAS GERAIS: Estrada Diamantina-Gouveia, ca. 4 km da cidade de Gouveia, Romero et al. 5390 (CAS-2!, HUFU, UEC!).

Figures

FIGURE 1. Images of Lavoisiera species. A. L. adamantium (Almeda et al. 8504). B–C. L. alba (Almeda et al. 9624). D–E. L. arachnoidea (unvouchered image). F. L. belinelloi (Almeda et al. 8532). G. L. bradeana (Almeda et al. 9718). H. L. canastrensis (Almeda et al. 7878). I. L. caryophyllea (Almeda et al. 9172). J–K. L. chamaepitys (Almeda et al. 8500). L. L. confertiflora (Almeda et al. 9725). Image credits: A–C, F–L. Frank Almeda; D–E. Karina Fidanza.

FIGURE 20. Distributions of Lavoisiera angustifolia, L. belinelloi, L. bradeana, L. punctata, L. sampaioana, L. scaberula, and L. tetragona.

FIGURE 24. Lavoisiera bradeana. A. Habit. B. Abaxial leaf surface with enlarged surface detail (upper right). C. Abaxial bract surface. D. Hypanthium and calyx lobes with enlarged detail of lobe margin (above). 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. J. Flower. (Based on: A–J, Irwin et al. 20850, UEC.)