Lavoisiera humilis Naudin (1844: 153)

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

Phytotaxa 315 (1) © 2017 Magnolia Press • 103 20. Lavoisiera humilis Naudin (1844: 153) . Type:— BRAZIL. Minas Gerais: “In campis arenosis editisque montium Serra do Frio ( Diamantina ), partis provinciae Minas Geraes dictae Distrito dos Diamantes,” A . Saint-Hilaire s.n. (holotype: P-00723379!; isotype: F!) .

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MARTINS & ALMEDA

= Lavoisiera serrulata Cogniaux in Martius (1883: 153). syn. nov. Type:— BRAZIL. Minas Gerais: G. Gardner 4579 (lectotype, here designated: G!; isolectotypes: BM!, E-00505255-n.v., online image!, F!, K-2!, NY!, P-05317922-n.v., online image!, W-2!).

Cespitose, sparingly branched subshrubs 10–20 cm tall with decumbent branches to 20 cm long, to erect, simple or branched subshrubs 20–80 cm tall, essentially glabrous. Branches and branchlets quadrangular and obscurely subalate, slightly furrowed longitudinally on opposite faces, the branchlets at first densely leafy to the base, defoliating and decorticating basally with age and then becoming subrounded; internodes 1–4 mm long, with knobby thickenings that persist where a leaf has fallen away, nodes surrounded by short, reddish, glandular trichomes. Juvenile leaves imbricate, sessile, typically restricted to short basal branchlets, blade 5–6 × 1–2 mm, linear-oblong, base rounded to attenuate, apex acute-mucronulate, margins entire to inconspicuous and sparsely serrulate-ciliolate, yellowish-green, 1(–3)-nerved; upper (mature) leaves sessile, semi-amplexicaul, erect and imbricate toward the shoot tips, blade 5–7 × 3–7 mm, subcoriaceous, oblong-ovate to ovate-suborbicular, base rounded to attenuate, apex obtuse, shortly mucronulate, margins subcallose to cartilaginous or not, serrulate-ciliate, the cilia frequently gland-tipped especially on the uppermost leaves, glabrous on both surfaces, margins and apex frequently flushed with purple, abaxial midvein sparsely serrulate-ciliate, subkeeled, yellowish-green or dark green, 1(–3)-nerved, gradually changing from the base to the apex, becoming wider toward the base of the flowers. Flowers (5–)6-merous, solitary, terminal but eventually becoming axillary or central by elongation of lateral shoots, sessile. Bracts several, petiole flat, ca. 1 mm long, blade 8–9 × 8–10 mm, ovate to suborbicular, apex obtuse-apiculate, margins serrulate, glandular-ciliolate to somewhat erose, membranaceous, pale green, 3–5- nerved. Hypanthium (at anthesis) 3–4 × 4 mm, broadly campanulate, glabrous, granulose at the apex. C alyx tube ca. 0.8 mm long; calyx lobes (at anthesis) 3.5–4 × 1.5–2 mm, membranaceous, persistent to tardily caducous, oblong-spatulate to obovate-oblong, apex rounded and shortly mucronulate, margins subcartilaginous and glandular-ciliolate, otherwise glabrous on both surfaces. Petals 10–12 × 6–8 mm, pink to deep pink and diffusely white to yellowish-green at the base, obovate, base attenuate, apex rounded to asymmetrically emarginate or obliquely but bluntly apiculate, base attenuate, margin entire or shortly and sparsely glandular-ciliolate. Stamens 10 or 12, dimorphic: large (antesepalous) stamens 5–6, filaments 5–6 mm long, yellow, anther thecae 2.5–3 × 1 mm, oblong, yellow, rostrum ca. 0.3 mm long, pedoconnective 4–5 mm long, appendage 1.5 mm long, subrounded to subtruncate, yellow; small (antepetalous) stamens 5–6, filaments 4 mm long, yellow, anther thecae 2–2.5 × 0.8 mm, oblong, yellow, rostrum ca. 0.3 mm long, pedoconnective 1–1.5 mm long, appendage 0.4 mm long, subrounded. Ovary 4-locular, 3/4 inferior, style 6–7 mm long, glabrous, curved apically and strongly declined to one side of the flower, stigma punctiform. Fruiting hypanthium (including calyx lobes) 5–7 mm long. Capsule (at maturity) 4–5 × 4–5 mm, enveloped by the persistent hypanthium, dehiscing from the base to the apex. Seeds 0.60–0.70 × 0.41–0.51 mm, oblong to somewhat curved, orangish-brown, periclinal cell walls of the testa concave (foveolate), raphal zone about 30–50% the length of the seed. Chromosome number unknown.

Illustrations:— Figure 42 ; Cogniaux (1883: t. 35, as L. serrulata ); Cogniaux (1883: t. 37).

Photographic images:— Figures 3E, F .

Phenology:—Flowering intermittently all year; fruiting in March and September but surely other months as well.

Distribution and habitat:—Restricted to the Diamantina plateau of the Cadeia do Espinhaço in the municípios of Diamantina and Gouveia, Minas Gerais, where it is local and uncommon in campo rupestre, brejo, sandy fields, gravelly slopes, and wet seepage areas at 1200–1415 m. Figure 16 .

Conservation status:—This species is known from some 16 collections representing about seven or eight populations on the Diamantina plateau. The EOO is 12 km ² and the AOO is 12 km ². In view of its narrow geographic and elevational distribution, habitat degradation, and the fact that none of the extant populations are in a protected area we recommend a classification of Critically Endangered (CR): B1ab(iii).

Discussion:—The diagnostic characters of Lavoisiera humilis are the sparingly branched habit, overall glabrosity, oblong-ovate to ovate-subcordate mature leaf blades that are ciliate-serrulate, 6-merous flowers, and 4- locular ovary. The most unusual feature of this species is the dimorphism exhibited by juvenile basal leaves versus mature upper cauline leaves. The immature basal leaves, which are ericoid in appearance, can completely cover decumbent young branches and conceal internodes. They are linear-oblong (1–2 mm wide) with an acute-mucronulate apex and entire margins. The wider mature leaves with distinctly ciliate-serrulate margins develop on more robust erect branches. Most collections of this species exhibit only the mature leaf form. Collections that

LAVOISIERA ( MELASTOMATACEAE )

Phytotaxa 315 (1) © 2017 Magnolia Press • 105 consist exclusively of mature leaf blades superficially look very different from those that show the transition from immature to mature leaf forms. Cogniaux was evidently unaware of the connection between these forms and described the mature forms as a distinctive species, L. serrulata , which is here relegated to synonymy. It is not surprising, therefore, that most collections of this species in herbaria that lack immature leaves have been identified as L. serrulata .

The leaves of Lavoisiera angustifolia resemble the juvenile leaves of L. humilis but the leaves of the former are somewhat larger (7–9 mm) with ciliate margins and the calyx lobes are triangular and sparsely covered with glandular hairs. Lavoisiera angustifolia also differs in having 5-merous flowers and a 5-locular ovary (vs. 6- merous and 5-locular).

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MARTINS & ALMEDA

At the one locality where we studied Lavoisiera humilis in the field (Almeda et al. 8497), we found it growing in close proximity to five other congeners ( L. adamantium , L. chamaepitys , L. crassifolia , L. imbricata , and L. mucorifera ). All of these sympatric species were in flower at the same time but we found no intermediates that could be interpreted as hybrids or introgressants.

Additional specimens examined:— MINAS GERAIS: Mpio. Diamantina , 4 km W of Hwy MG 220 along the road to Conselheiro Mata , 18°16'S, 43°42'W, Almeda et al. 8497 (CAS!, K!, MO!, NY!, P!, UEC!, US!); Mpio. Diamantina , 4 km W of Hwy MG 220 along the S side of the road to Conselheiro Mata , 18.27630°S, 43.71281°W, Almeda et al. 9603 (BHCB!, CAS!, NY!, UEC!); Mpio. Diamantina , 18 km W of Hwy MG 220 along the road to Conselheiro Mata , 18.30142°S, 43.82372°W, Almeda et al. 9626 (CAS!, UEC!); Mpio. Conselheiro Mata, Brade 13722 (MO!, NY!, R!); Mpio. Diamantina , próximo a AABB, Braga & Chaves 441 (SPF!); Mpio. Gouveia?, entre Fazenda Contagem e Fazenda Prata, Cordeiro et al. CFCR 588 (CAS!, SPF!, UEC!, US!); Mpio. Diamantina, Diamantina-Extração , a 7 km de Diamantina, Furlan et al. CFCR 2278 (SPF!, US!); Mpio. Diamantina, Gardner 4580 (BM); Biribiri, Glaziou 19258 (BR-3!, C!, F-2!, G!, K!, LE!, NY!, P!, R!, RB!, US-2!); Mpio. Diamantina, Serra dos Cristais, Glaziou 19259 (BR-2!, C!, G!, LE!, P!, US!); Mpio. Conselheiro Mata , estrada entre Diamantina e Conselheiro Mata, Grandi et al. 8046 (HUFU-2!); Mpio. Diamantina, Ribeirão das Pedras, Hatschbach & Pelanda 27922 (MBM!, US!); Mpio. Diamantina, Serra do Espinhaço, Hatschbach 27492 (MBM!, US!); ca. 2 km S of São João da Chapada, Irwin et al. 28377 (F!, MICH!, MO!, NY!, RB!, US!); Mpio. Diamantina, Arranca Rabo, Mello Barreto 9394 (F!); Mpio. Diamantina, Natureza, Mello Barreto 9717 (BHCB ex BHMH!, F!, NY!); Mpio. Diamantina , Rio Prata, Pereira 1660 (F!, RB!); Mpio. Diamantina, Riedel 1226 (BR!, LE!, NY!).

Figures

FIGURE 3. Images of Lavoisiera species. A. L. grandiflora (unvouchered image). B−C. L. grandiflora (Almeda et al. 9459). D. L. harleyi (unvouchered image). E−F. L. humilis (Almeda et al. 8497). G. L. imbricata (Almeda et al. 8497). H. L. imbricata (Almeda et al. 9032). I−K. L. itambana (Almeda et al. 9663). L. L. macrocarpa (Almeda et al. 8545). Image credits: A. Pinterest at www.pictopin.com; B, C, E−L. Frank Almeda; D. Fernando B. Matos.

FIGURE 16. Distributions of Lavoisiera adamantium, L. firmula, L. humilis, L. pulcherrima, and L. subulata.

FIGURE 42. Lavoisiera humilis. A. Habit. B. Adaxial leaf surface. C. Adaxial bract surface. D. Flower. E. Hypanthium and calyx lobes with enlarged calyx lobe margin detail (right). F. Ovary cross-section. G. Petal with enlarged 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. 8497, CAS, UEC.)