Miconia latidecurrens Gamba & Almeda

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: PANAMA. Prov. Colón: Donoso, Coclé del Norte, área del helipad TO2A, tomando la ruta S, a orilla de una trocha, 08°53’28”N, 80°40’42”W, 110 m, 18 July 2012, Martínez 880 (holotype: CAS!; isotype: PMA).

Comments: Related to M. laxivenula with which it shares the glabresecent appearance and laxly reticulate leaves. Distinguished by its widely decurrent leaf bases all along the petioles, and 5-merous flowers.

Description: Slender treelet to 3 m. Upper internodes 3.35–6.61 cm long, compressed-rounded and weakly to moderately carinate, cauline nodes rounded-compressed, nodal line present as a minute ridge. Indumentum on branchlets, primary and secondary leaf veins abaxially, inflorescence axes, bracts, bracteoles, pedicels, hypanthia, calyx lobes and calyx teeth sparsely and caducously composed of resinous amorphous lepidote trichomes ca. 0.2 mm long with only partially fused radii. Leaves of each pair isophyllous; sessile; blades 29.2–43.8 × 11.5–13.8 cm, oblong-elliptic, the base attenuate and widely decurrent on the petiole extending to the node, the margin entire, the apex bluntly short-acuminate, chartaceous; mature leaves adaxially glabrous like the primary, secondary, tertiary and higher order veins; abaxial surface reddish, superficially glabrous, microscopically papillose with rounded glands ca. 0.02 mm in diameter, the tertiary and higher order veins glabrous; 5-plinerved, including the tenuous marginals, innermost pair of secondary veins diverging asymmetrically from the primary vein 5.5–9.5 cm above the decurrent base, areolae 2–5 mm, adaxially the primary, secondary and tertiary veins impressed, the higher order veins flat, abaxially the primary and secondary veins elevated and prominently carinate, the tertiary and higher order veins slightly elevated to flat. Inflorescences an erect pseudolateral dithyrsoid 12–13.5 cm long, including a compressed-rounded peduncle 2.8 cm long, divaricately branched from the peduncle apex, borne in the upper foliar axils; bracts 0.8–1 × 0.7 mm, bracteoles 1–1.2 × 1 mm, deltoid-concave, with the bases of each pair confluent to form a well-defined deflexed flaplike outgrowth that encircles the pedicel base and nodes of the inflorescence axes, persistent in fruit. Flowers 5-merous on pedicels 0.3 lengthening 0.5 mm long in fruit, the central flower of each dichasium sessile. Hypanthia at anthesis 2.2–2.3 × 1.6–1.8 mm, free portion of hypanthium ca. 1 mm long, globose to somewhat urceolate, bluntly 10-ribbed, ridged on the inner surface, minutely beset with sessile translucent glands, the torus adaxially puberulent with subulate fine trichomes. Calyx open in bud and persistent in fruit; tube 0.3–0.4 mm long, glabrous adaxially, with the same vestiture as the hypanthium abaxially; lobes 0.2–0.3 × 0.6 mm, vaguely undulate, the margin entire, the apex rounded-truncate; exterior calyx teeth to ca. 0.3 mm long, tuberculiform, inserted at the base of the lobes and barely projecting beyond them. Petals 4–4.2 × 1.5 mm, oblong, the margin entire, the apex rounded, white, glabrous on both surfaces, erect to somewhat spreading at anthesis. Stamens 10; filaments 1.6–1.7 × 0.3–0.4 mm, white, glabrous; anther thecae 1.5–1.7 × 0.4 mm, oblong and slightly clavate, emarginate at the apex, opening by two dorsally inclined pores 0.1–0.2 mm in diameter, white and browning with age; connective somewhat darker than the thecae, its prolongation and appendage 0.4–0.5 mm long, the appendage oblong, rounded at the apex, copiously gland-edged, the glands stalked with rounded-flattened heads, becoming sparse on the rest of the connective dorsally, white. Ovary 5-locular, 2/3 inferior, 1.7–1.8 mm long at anthesis, the apical collar 0.5 × 0.3–0.4 mm, conic, minutely glandular-puberulent apically; style 6–6.5 mm long at anthesis, narrowed distally (i.e. tapering), white, glabrous; stigma expanded-truncate. Berries 3.32–3.42 × 3.6–4.43 mm when dry, globose-oblate, white when ripe, the hypanthial indumentum subpersistent at maturity. Seeds 0.49–0.55 × 0.16–0.18 mm, ovoid-angled to somewhat pyramidal, shiny-brown; lateral and antiraphal symmetrical planes triangular to suboblong, the highest point toward the chalazal side; raphal zone suboblong, as large as to 100% larger than the corpus of the seed, ventrally expanded throughout its length becoming larger at the chalazal end, shiny-whitish; individual cells elongate, anticlinal boundaries channeled, undulate, with ?- and U-type patterns; periclinal walls convex, low-domed to nearly flat, microrelief verrucose to somewhat striate.

Habitat and Distribution: Known from the westernmost part of the province of Colón in Panama, disjunctly to Alto Pacora, and in La Virgen in Costa Rica , at 60–700 m. Most of the collections are from lowland forests on steep slopes near the site of a copper mine in Panama (60–155 m), and there is one record from a higher elevation (700 m) tropical wet forest on a trail that connects Alto Pacora with Cerro Brewster. In its restricted range this species is commonly found close to streams.

Phenology: Collected in flower and fruit in July and August; with inmature flowers in August, and only in fruit in April, September and November.

Etymology: The specific epithet refers to the large widely decurrent leaf bases of this species.

Taxonomy and Systematics: This species can be readily recognized by its widely decurrent foliar bases that extend all the way to the node, superficial glabrosity throughout, and 5-merous flowers. The Panamanian individuals have leaves that are laxly reticulate and reddish abaxially. This coloration is not present in the one Costa Rican collection. It most resembles M. laxivenula which has similar caducous squamate-amorphous indumentum and laxly reticulate leaves, but with prevailingly 4-merous flowers and leaves that are never sessile. The decurrent leaf bases and large leaves are similar to M. sessilis, which has a more obvious puberulent indumentum and 4-merous flowers.

Conservation Status: This species would be considered Endangered EN B2ab(iii) based on IUCN criteria (AOO). Althought it occurs in an area that will become protected, the AOO, its fragmented habitat and its destruction result in this taxon being relegated to the threatened category of Vulnerable VU. This species is considered not endangered by the MPSA database. The MPSA is a mining concession in Panama that is currently evaluating the plant diversity around the mine areas with assistance from staff botanists at the Missouri Botanical Garden and collaborating specialists. This species was recently collected in what would become a protected area around the mine.

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