Graffenrieda maturaca, Lima, Laíce Fernanda Gomes De, Baumgratz, José Fernando Andrade, Lughadha, Eimear Nic & Santos, João Ubiratan Moreira Dos, 2016

Lima, Laíce Fernanda Gomes De, Baumgratz, José Fernando Andrade, Lughadha, Eimear Nic & Santos, João Ubiratan Moreira Dos, 2016, Two new species of Graffenrieda (Melastomataceae, Merianieae) from the Amazon Rainforest, Phytotaxa 267 (1), pp. 77-83 : 78-80

Graffenrieda maturaca L.F. Lima, Baumgratz, NicLugh. & J.U.Santos sp. nov. ( Figure 1 )

Type : — BRAZIL. Amazonas : São Gabriel da Cachoeira , Alto Rio Negro , estrada para Cucuí, BR 307, destacamento de Maturacá, Serra de Maturacá (= Serra do Padre), 300–400 m alt., 27 November 1987 (fr.), H.C. Lima et al. 3310 (holotype RB!; isotypes INPA, NY!) .

This species resembles G. lanceolata , differing in its leaves with petioles 8–15 mm long, laminas dull on the adaxial surface, chartaceous, narrowly elliptic to oblanceolate, apex acute, base acute to cuneate, apparently uni-nerved, median acrodromous vein conspicuous, marginal pair imperfectly developed, very fine towards base, transverse secondary venation and higher order venation not visible on the leaf surface adaxially or abaxially.

Treelet ca. 6 m tall. Indumentum of the branches and leaves moderately pulverulent, ferrugineous, trichomes soon falling. Young branches quadrangular. Leaves with petioles 8–15 mm long, striate, glabrescent; laminas 5–5.5 × 1.2–1.5 cm, dull on the adaxial surface, chartaceous, glabrescent, narrowly elliptic to oblanceolate, apex acute, base acute to cuneate, margin entire, revolute; apparently uni-nerved, median acrodromous vein conspicuous, marginal pair imperfectly developed, very fine towards base, transverse secondary venation and higher order venation not visible on the leaf surface adaxially or abaxially. Inflorescences not seen. Flowers 4-merous, subsessile, senile in the specimen examined; petals ca. 7 × 3 mm, spathulate, apex asymmetric; stamens isomorphic, filaments ca. 4 mm long, apical portion of the anthers not seen, connective not prolonged below the thecae, basal dorsal spur ca. 1 mm long, linearacute. Infructescence a cyme, ca. 8.5 mm long, terminal, pedunculate, with fruits in glomerules and triads, glabrous; peduncle ca. 4.6 cm long; bracts leafy, ca. 3 × 0.5 cm; bracteoles ca. 1 × 1 mm, thick, triangular-denticulate. Capsule of the velatidium type, greenish-wine coloured when young, brown when mature, 3-valvate, glabrous, multi-seeded, subsessile; pedicel ca. 1 mm long; hypanthium ca. 4 × 3 mm, shortly-tubular, lightly costate; remaining calyx lobes irregular, ca. 1 mm long, tube 0.6–0.7 mm long; mature ovary ca. 3 × 2 mm, trilocular; seeds 0.8–1 × ca. 0.3 mm, light brown, obpyramidal-cuneate.

Distribution and habitat:— Graffenrieda maturaca is known from a single collection made in the upper reaches of the Rio Negro, at Serra de Maturacá, municipality of São Gabriel da Cachoeira, where it is reported as being ‘occasional’ in low forest on slopes. According to the collector (pers. comm.), the type specimen occurs in low vegetation comprising trees and shrubs, on thin soil with rocky outcrops.

Etymology:— The epithet “maturaca ” refers to the mountain range where the type specimen was collected in the state of Amazonas, Brazil.

Conservation status:—Data Deficient (DD). The single collection of G. maturaca was made within the Parque Nacional do Pico da Neblina, in Amazon Forest of Amazonas state, which suggests that it is not under immediate threat. However, at present, we can not assess the extinction risk of this species, because there are scarce data about biological, ecological and species distribution, and it is necessary to undertake fieldwork to increase new information.

Discussion:— Graffenrieda maturaca can be recognized mainly by the leaves with petioles 8–15 mm long, laminas dull on the adaxial surface, chartaceous, narrowly elliptic to oblanceolate, apex acute, base acute to cuneate, apparently uni-nerved, median acrodromous vein conspicuous, marginal pair imperfectly developed and very fine towards base, secondary transverse and higher order venation inconspicuous on the adaxial surface of the leaf. Among the species already described, G. maturaca is most similar to G. lanceolata Gleason (in Steyermark 1952: 432), a species endemic to Monte Duida, in Venezuela, and also known only from fruiting collections. However, the latter differs from G. maturaca in having leaves with a shorter petiole (4–8 mm long) and lamina with adaxial surface shining, narrowly lanceolate, apex long-acuminate, base obtuse to shortly rounded, 3 acrodromous nerves conspicuous, the marginals thick and evident on both faces, being impressed on the adaxial face, secondary venation conspicuous in the adult leaves. Another similar species is G. pedunculata Gleason (in Maguire 1953: 135), endemic to the Serra do Sipapo, in Venezuela, but differing in presenting young branches narrowed, blackened, with short internodes, and with two to three pairs of leaves at the apex, leafless to the base, leaf lamina coriaceous, inflorescences with long peduncles (8–15 cm long), and ovary 2-locular.

That such a distinctive species has remained undescribed for nearly three decades after it was collected is perhaps attributable to the limited material available, and the paucity of recent taxonomic studies on the genus. While some taxonomists might hesitate to describe a new species based on a single fruiting collection, our decision may be justified by the distinctive characters outlined above and supported by the discovery of floral fragments adhering to one of the fruit on NY specimen which allowed us to confirm the isomorphic nature of the stamens, a key character for the genus.

Graffenrieda maturaca resembles several other Graffenrieda species described over recent decades in being apparently endemic to a single country and having a restricted geographic range ( Gleason 1952, 1953, Wurdack 1964, Almeda et al. 2014, Michelangeli & Goldenberg 2014). However, plant collection densities are so low in the vicinity of the type locality that it is possible that G. maturaca will eventually be found to have a wider distribution, perhaps even with a range extending into Amazonian forest vegetation of neighboring countries such as Venezuela, Peru or the Guianas, as is the case for other Graffenrieda species (Macbride 1941, Wurdack 1973, 1980, Wurdack & Renner 1993, Lima, in prep.).

Figures

FIGURE 1. Graffenrieda maturaca. A. Fructiferous branch; B. Abaxial surface of leaf showing midrib and revolute margin; C. Detail of stamen appendage; D. Fruit; E. Fruit with hypanthium partially removed showing mature ovary; F. Longitudinal section of fruit showing seeds (Lima 3310).