Lavoisiera arachnoidea Almeda & A. B. Martins, 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

4. Lavoisiera arachnoidea Almeda & A. B. Martins , sp. nov.

Erect, open fastigiately branched subshrubs 30–70 cm tall, perennating from a lignotuber. Branches sparsely arachnoidpuberulous, trichomes caducous. Leaves sessile, coriaceous, apex typically recurved distally, margins slightly revolute, subcallose, ciliate at least on the distal half, abaxial surface sparsely arachnoid-puberulent, inconspicuously reticulate, adaxial surface glabrous, greenish-gray, 5–7-nerved. Flowers 5–6 merous, solitary. Hypanthium sparse to moderately arachnoid-puberulent. Petals reportedly pink or purplish with yellowish base. Ovary 5–6-locular, 3/4 inferior.

Type:— BRAZIL. Distrito Federal: “ Encosta do Morro da Canastra à base da escarpa, 15º35'S, 47°54'W,” 16 December 1981, J. H. Kirkbride Jr. 4588 (holotype: RB!; isotypes: F!, INPA, K!, MBM!, NY!, SP, UB, US!) .

Erect, open fastigiately branched subshrubs 30–70 cm tall, perennating from a lignotuber. Branches and branchlets quadrangular to subquadrangular, longitudinally furrowed, yellowish-green turning to brown, sparsely arachnoid-puberulent, the trichomes caducous, branchlets leafy to the base, defoliating and decorticating basally with age, basal branches with scattered hirtellous to hirsute trichomes ca. 2 mm long; internodes 3–10 mm long, with knobby thickenings that persist where a leaf has fallen away, nodes with inconspicuous glandular trichomes. Leaves sessile, spreading to subimbricate distally; blade 6–9 × 4–7 mm, coriaceous, ovate to oblong-ovate, base rounded, apex acute-acuminate, typically recurved distally, terminating in a pungent trichome, margin occasionally slightly revolute, sometimes subcallose, ciliate at least on the distal half, the cilia pungent and ca. 2 mm long, greenish-gray to yellowish-green and glabrous on the adaxial surface, greenish-gray, sparsely arachnoid-pulverulent and sometimes with a few scattered spreading trichomes on the abaxial surface of young leaves, inconspicuously reticulate, 5–7-nerved, the midvein with a few strigose trichomes. Flowers 5–6-merous, solitary, terminal at ends of principal or lateral branchlets, becoming central with the growing of lateral branchlets, sessile. Bracts subtending the flowers several, congested, blade 6–7 × 8 mm, shortly petiolate, the petiole flat, ca. 1 mm

LAVOISIERA ( MELASTOMATACEAE )

Phytotaxa 315 (1) © 2017 Magnolia Press • 51 52 • Phytotaxa 315 (1) © 2017 Magnolia Press

MARTINS & ALMEDA LAVOISIERA ( MELASTOMATACEAE )

Phytotaxa 315 (1) © 2017 Magnolia Press • 53 long, ovate to suborbicular, apex acute-acuminate strongly curved, margin ciliate, the marginal trichomes incurved, up to 9-nerved, flushed with red at the base, similar to the principal leaves. Hypanthium (at anthesis) 4 × 3–4 mm, broadly campanulate, sparsely to moderately arachnoid-pulverulent or often with inconspicuous minute delicate rod-like trichomes especially toward the distal end ( Figure 21D ). Calyx tube ca. 0.5 mm long; calyx lobes (at anthesis) 6 × 3.5 mm, chartaceous, ovate to ovate-oblong, apex acute with a terminal trichome, revolute, margins ciliate with incurved trichomes, the sinus between the lobes often forming a conspicuous circular opening, arachnoid-pulverulent on both surfaces, caducous in post-anthesis, flushed with red. Petals 20–25 × 8 mm, reportedly pink or purple with a yellow base (the buds white but pink distally), oblong to narrowly spatulate, apex asymmetrically truncate, base attenuate, margin eciliate. Stamens 10 or 12, dimorphic: large (antesepalous) stamens 5–6, filaments 1.4–1.5 mm long, anther thecae 4.5–5.5 × 1 mm, linear-oblong, yellow flushed with red but becoming purplish when dry, rostrum 0.5 mm long, pedoconnective ca. 10 mm long, appendage 1.5–2 mm long, slightly emarginate and bilobed; small (antepetalous) stamens 5–6, filaments 0.7–0.9 mm long, anther thecae 3.5–4 × 0.8 mm, linear-oblong, yellow, rostrum ca. 0.5 mm long, pedoconnective 2 × 3 mm long, appendage 1 mm long, truncate to obscurely bilobed, yellow. Ovary 5–6-locular, 3/4 inferior, style 15 mm long, slightly curved apically, stigma punctiform. Fruiting hypanthium (including calyx lobes) ca. 12–13 mm long. C apsule (at maturity) ca. 9 mm long, globose, coriaceous, maroon to reddish, enveloped by the persistent hypanthium, dehiscence unknown. Seeds 0.94–1.13 × 0.46–0.57 mm, oblong, orangish-red, periclinal cell walls of the testa concave (foveolate), the raphal zone about 70% the length of the seed. Chromosome number unknown.

Illustration:— Figure 21 .

Photographic images:— Figures 1D, E .

Phenology:—Flowering April, June, November, and December; fruiting April, November, and December.

Distribution and habitat:—Restricted to the Distrito Federal and Goiás in rocky soil in cerrado at 975–1200 m elev. Figure 22 .

Conservation status:—This species is known from five small populations represented by as many collections. All but one of these were collected in cerrado habitats in the Distrito Federal over 30 years ago. The EOO and AOO are each 8 km ². Because of its limited area of occupancy in an area that has experienced massive urban growth with ongoing modification of cerrado environments we recommend a classification of Critically Endangered (CR): B2ab(iii).

Discussion:—The most distinctive characters of L. arachnoidea are its open fastigiate habit with crowded decussate leaf blades that are recurved distally and terminate in a pungent trichome ( Figures 1D, E ; 21A, C ). The blade margins have pungent cilia-like trichomes that are ca. 2 mm long and the uppermost internodes, abaxial surfaces of the uppermost leaves, and hypanthia are covered with an arachnoid indumentum.

In foliar morphology, L. arachnoidea resembles L. quinquenervis and L. setosa , both of which are also little-collected cerrado species known only from the Distrito Federal and/or Goiás. The former is readily distinguished by its uppermost internodes that are glabrous to inconspicuously and sparsely covered with minute glandular trichomes, serrulate-denticulate leaf margins that are glandular-ciliate, and glabrous hypanthia. The characters distinguishing L. arachnoidea from L. setosa are enumerated in the discussion under the latter.

Etymology:—The specific epithet is derived from the Latin word arachnoideus = cobwebby, alluding to the indumentum of tangled cottony hairs on the uppermost internodes, abaxial surfaces of the uppermost leaf blades, and hypanthia.

Additional specimens examined:— DISTRITO FEDERAL: Córrego Jeriva, East of Lagoa Paranoá , Irwin et al. 15382 ( NY!, US!) ; Mpio. Brasília, Est. Sobradinho, Occhioni 2174 ( US!); Mpio. Brasília, Cachoeira do Colorado, próximo à fábrica de asfalto, 15°35'S, 47°53'W, Simon et al. 65 ( E, NY-2!, UB). GOIÁS: Mpio. Agua Fria, Estação Repetidora da Telebrasília de Roncador, Hatschbach et al. 59317 ( FURB, MBM!, UEC, US!) .

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 21. Lavoisiera arachnoidea. A. Habit. B. Abaxial leaf surface. C. Abaxial bract surface. D. Hypanthium and calyx lobes with enlarged surface detail (left) and enlarged adaxial intercalycine detail (right). E. Ovary cross-section. F. Petal. G. Ventralview of antesepalous stamens. H. Lateral view of antepetalous stamen. I. Seed. (Based on: A, Kirkbride 4588, US; B–I, Irwin et al. 15382, NY.)

FIGURE 22. Distributions of Lavoisiera arachnoidea, L. confertiflora, L. daviesiana, L. harleyi, L. mellobarretoi, L. nervulosa, and L. rundeliana.