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Family:

Melastomataceae (Magnoliophyta)

Primary Citation:

Systematics of the octopleura clade of Miconia (Melastomataceae: Miconieae) in tropical America
Phytotaxa 179: 1--174. 2014

Accepted Name:

This name is currently accepted.

Description:

Description Author and Date: Diana Gamba & Frank Almeda, modified from "Systematics of the Octopleura Clade of Miconia (Melastomataceae: Miconieae) in Tropical America". Gamba, D., Almeda, F. Phytotaxa 179(1): 1-174.

Type: ECUADOR. Prov. Pastaza: Mera, in forest near Alpayacu, ca. 1100 m, 23 November 1955, Asplund 18577(holotype: S). Nec Miconia asplundii Wurdack (1972: 202–203).

Description: Subshrub or shrub 0.5–4 m tall with moderate to lax branching, bark brownish. Upper internodes [(0.6–)1.3–4.2 cm long] and cauline nodes terete, nodal line absent. Indumentum on branchlets, petioles, primary, secondary and tertiary veins abaxially, inflorescence axes, bracts, bracteoles, and pedicels densely to copiously composed of brownish clavate stipitate dendritic trichomes 0.053–0.093 mm long with short to moderately long thin-walled (flattened) arms. Leaves of each pair slightly unequal in size, the younger pairs isophyllous; the petiole 0.4–1.6 cm long, superficially canaliculate adaxially and moderately grooved abaxially, green; larger blades 8.2–10.9(–16.8) × 3.15–5 cm, smaller blades 4–10.5 × 1.5–3.6 cm, elliptic-lanceolate, the base bluntly acute to rounded, the margin entire, the apex caudate-acuminate, firm-chartaceous; mature leaves adaxially moderately to sparsely covered with the dendritic trichomes becoming glabrescent, the primary, secondary, tertiary and higher order veins glabrous; abaxial surface superficially glabrous except for a few glands on the venules, microscopically papillose with rounded glands, the tertiary and higher order veins copiously to moderately beset with white furrowed sessile glands 0.03–0.04 mm long, copiously intermixed with and occasionally replaced by resinous glands of the same type; 5-(7-) plinerved, including the tenuous marginals, innermost pair of secondary veins diverging from the primary vein somewhat asymmetrically 0.3–0.6 cm above the base, areolae 0.25–0.5 mm, adaxially the primary and secondary veins flat, the tertiary and higher order veins impressed, abaxially the primary and secondary veins elevated and terete, the tertiary and higher order veins slightly elevated to flat. Inflorescences an axillary cluster of few-flowered cymes (5–7-flowered) 1.5–3.5 cm long, including a peduncle 0.13–1.13 cm or sessile, branching poorly developed with multiple axis arising from a common point at the peduncle apex or at the base (then fascicle-like), paired, borne in the upper leaf axils and also on defoliated nodes, the rachis typically pinkish; bracts 0.45–0.95 × 0.2–0.3 mm, linear-oblong and subulate, erect, bright pink, the dendritic trichomes copiously intermixed with white furrowed sessile glands; bracteoles 0.35–0.75 × 0.1–0.3 mm, linear-oblong, spreading, pinkish, along with bracts early deciduous at anthesis but occasionally persistent in fruit. Flowers 4-merous on pedicels 0.25–1 mm lengthening to 1.5 mm in fruit. Hypanthia at anthesis 1.4–1.6 × 1–1.5 mm, free portion of hypanthium 0.5–1 mm long, subcylindric to slightly campanulate, bluntly 8-ribbed, pink, copiously beset with white furrowed sessile glands 0.04–0.05 mm long, typically copiously intermixed with resinous glands of the same type, ridged on the inner surface, glabrous, the torus adaxially sparsely resinous-glandular. Calyx open in bud and persistent in fruit, pinkish becoming green in fruit; tube 0.09–0.27 mm long, with the same vestiture as the torus adaxially, and as the hypanthium abaxially; lobes 0.75–1.09 × 0.85 mm, broadly and bluntly triangular, the margin entire, the apex bluntly acute, glabrate, reflexed at anthesis and fruit; exterior calyx teeth 0.6–1.3 mm long, bluntly subulate, inserted half way up and projecting beyond the calyx lobes, glandular like the hypanthium. Petals2.13–2.53 × 0.75–1.05 mm, narrowly lanceolate and wider at the base, the margin entire, the apex bluntly acute to acuminate, white, glabrous on both surfaces, reflexed at anthesis. Stamens 8; filaments ca. 1–1.5 × 0.25 mm, white, glabrous; anther thecae 1.4–1.6 × 0.31–0.43 mm, linear-oblong, truncate-emarginate at the apex, opening by one dorsally inclined pore 0.11–0.15 mm in diameter, white to light yellow at anthesis; connective white to yellow, its prolongation and appendage 0.25–0.5 mm long, the appendage lanceolate, acute at the apex, copiously beset with glandular trichomes from the edges to the center, with fewer glands of the same kind throughout the connective, which is also somewhat prolonged and gland-edged but unappendaged ventro-basally. Ovary 4-locular, 2/3 inferior, 0.7–1 mm long at anthesis, the apical collar absent, the apex 0.2–0.3 mm in diameter, conic, sparsely glandular-puberulent; style 3.5–3.7 mm long, parallel-sided (i.e. terete) to narrowed distally (i.e. tapering), white, glabrous; stigma capitellate at anthesis (truncate when dry). Berries 2.18–3.09 × 3.03–3.37 mm when dry, globose-oblate, initially bright pink, then green, ripening purple-black, the hypanthial indumentum somewhat persistent at maturity. Seeds 0.49–0.53 × 0.24–0.28 mm, pyramidal, brownish; lateral symmetrical plane triangular, the highest point near the central part of the seed; antiraphal symmetrical plane suboblong; raphal zone circular to suboblong, ca. 60% the length of the seed; multicellular sculpture rugose throughout the seed; individual cells and microrelief not readily discernable on any of the known collections.

Habitat and Distribution: Growing in the understory, usually close to streams of primary or secondary (sometimes disturbed) cloud forests, from Costa Rica to the Atlantic slope of Panama, becoming rare in Colombia and Ecuador, at (5–)600–1700 m. Miconia alboglandulosa is reported here for Colombia for the first time, where it is known from Chocó, Cauca, one other collection from an unusually low elevation site (five meters) on the Pacific coast in this same department, and Risaralda. It probably also occurs in the Nariño (Colombia)-Esmeraldas-Carchi region, a continuation of the Chocó.

Phenology: Collected in flower from November through March, and May through August; in fruit from September through March, and June to July.

Etymology: The specific epithet refers to the dense white furrowed glands present on the leaves abaxially and on the hypanthia.

Taxonomy and Systematics: This species is notable for its minute pulverulent dendritic trichomes on vegetative and floral parts, densely glandular abaxial foliar surfaces (with both white and resinous sessile furrowed glands), and bright pink hypanthia that turn purple-black at maturity. For unknown reasons the seeds adhere to one another in dried herbarium material in a way that makes it nearly impossible to collect and study adequately under a dissecting microcope. From the phylogenetic analyses performed in this study it was confirmed that M. albogalndulosa is closer to the species in the Approximata subclade. It is in a basal position within this subclade. Miconia alboglandulosa is more similar to M. aurantiaca, which shares a similar vegetative pulverulent-furfuraceous indumentum (described as granulose-furfuraceous in M. aurantiaca reflecting the size difference) and similar inflorescence architecture (fascicle-like cluster of cymes). Microscopically, the abaxial foliar surfaces in both species are papillose with rounded glands; more detailed foliar anatomical studies are needed to assess the consistency of this character. Miconia alboglandulosa differs in having a typically pink hypanthium (vs. green in M. aurantiaca and relatives), purple-black berries at maturity (vs. bright orange or reddish), and larger inflorescences (1.5–3.5 vs. 0.25–1.15 cm long in M. aurantiaca). Other microscopic differences include the dense mixture of resinous and white furrowed glands on the abaxial foliar venules and hypanthia (vs. glands prevailingly white and hypanthia pulverulent-furfuraceous and sparsely glandular).Yet another species (M. renatoi) that is distinct from but probably a sister species of M. alboglandulosa has been collected in Ecuador (Carchi, Pichincha and Cotopaxi), and Colombia (La Planada Reserve, Nariño). Both share the pink hypanthial color and the purple-black mature berries, and in both the seeds are difficult to isolate from the dried berries for study. This latter taxon is described as a new species in this study (see citation of specimens under its description), and is clearly different from M. alboglandulosa in lacking the white resinous furrowed glands on the abaxial foliar venules and hypanthia. Instead it is just covered with a whitish-furfuraceous indumentum. It is also distinct in foliar details (elliptic-lanceolate and rounded in M. alboglandulosa vs. elliptic and acute to attenuate), and venation 5-(7-) plinerved (vs. 5-(7-) nerved). Moreover, it has a different indumentum on the cauline internodes, nodes and primary foliar veins abaxially that consists of somewhat flattened elongate slightly to moderately roughened trichomes, similar to the ones present in M. chocoensis. There is another collection from Ecuador (Clark 4676, QCNE, MO, NY!) that most likely represents an undescribed species close to M. alboglandulosa. The duplicate studied has inmature fruits, which precludes the description of this taxon as a new species. The specimen is similar to M. alboglandulosa in its inflorescences that consist on groups of modified cymes, calyx lobes that are conspicuously reflexed, and calyx teeth that project beyond the lobes. The sparse vegetative indumentum of this individual is composed of minute dark brown dendritic trichomes with short thin-walled arms (ca. 0.1 mm long); the hypanthium and calyx lobes have few sessile resinous furrowed glands. This type of indumentum also suggests the evolutionary proximity of this species to those in the Approximata clade. This entity differs in its glabrous appearance and in having sessile leaves, some pairs being amplexicaul, a character that is present in few species of Octopleura which are not closely related to species in the Approximata clade.

Conservation Status: Endangered EN B2ab(iii), and protected only in two countries of its range. It was considered Rare in previous conservation assessments, which is not considered an IUCN Red List category at present (IUCN Standards and Petitions Subcommittee 2013). Rare taxa are usually localized within restricted geographical areas or habitats or are thinly scattered over a more extensive range (Walter & Gillett 1998). In Colombia this species is protected in Tatamá National Park (Risaralda). In Costa Rica, the protected areas from which this species is known include the Monteverde Biological Reserve (Alajuela), Tapantí National Park, La Marta Wild Life Refuge (Cartago), Braulio Carrillo National Park (Heredia), and the Río Banano Protected Zone (Limón).