Miconia formicaria Gamba & Almeda, 2014

Gamba, Diana & Almeda, Frank, 2014, Systematics of the Octopleura Clade of Miconia (Melastomataceae: Miconieae) in Tropical America, Phytotaxa 179 (1), pp. 1-174 : 80-81

16. Miconia formicaria Gamba & Almeda , spec. nov. ( Fig. 21 )

Related to M. bractiflora in having the secund arrangement of flowers in the dichasial ramifications of the paracladia. It is distinct in the presence of a conspicuous formicarium at the blade base adaxially.

Type: COLOMBIA. Dept. Valle: Mpio. Dagua, corregimiento El Queremal, P.N.N. Farallones, Alto Anchicayá. Trail off of (upslope) Quebrada La Riqueza. Cordillera Occidental , vertiente occidental, 03°39.998’N, 76°53.609’W, 600–810 m, 6 February 2011, Almeda et al. 10274 (holotype: COL!; isotypes: CAS!, CAUP!, CUVC!, FMB!, HUA!, NY!, PSO!) .

Subshrub 1 m tall, little-branched, bark green-brownish. Upper internodes rounded-quadrate and somewhat grooved, ca. 3 cm long, cauline nodes terete, nodal line present and frequently obscured by the dense indumentum. Indumentum on branchlets, primary and secondary leaf veins abaxially, and inflorescence axes densely composed of brown-translucent somewhat flattened, slightly elongate moderately roughened trichomes 0.2–0.4 mm long, copiously to moderately intermixed with, and replaced on petioles, tertiary leaf veins abaxially, bracts, bracteoles, hypanthia, exterior calyx teeth, and petals abaxially by resinous-whitish dendritic trichomes 0.1–0.2 mm long with moderately long thin-walled (flattened) arms. Leaves of each pair isophyllous; the petiole 0.76–0.89 cm long, deeply and narrowly canaliculate adaxially, irregularly grooved abaxially, greenish, the dense dendritic indumentum moderately intermixed with resinous slightly furrowed more or less stalked glands ca. 0.05 mm long; blades 15–23.6 × 8.2–11.1 cm, ovate, tapering to a rounded-cordate base, the margin vaguely crenate, the apex bluntly long-acuminate, chartaceous; mature leaves adaxially glabrous with conspicuous formicaria ca. 8 × 2.5 mm at the base, the formicaria forming two half-oval sacs, moderately setose with elongate smooth trichomes 4–5 mm long, the primary, secondary, tertiary and higher order veins glabrous; adaxial surface superficially glabrous, microscopically papillose with brown to resinous rounded glands ca. 0.05 mm in diameter, the indumentum on the primary, secondary and tertiary veins somewhat caducous, the higher order veins glabrous; 7-nerved to 7-plinerved, including the tenuous marginals, innermost pair of secondary veins diverging from the primary vein 0.5–0.6 cm above the base, abaxially forming a deep pocket-like space (acarodomatium?) covered with trichomes like those of the the general indumentum on the primary and innermost pair of secondary veins, areolae 0.5–1 mm, adaxially the primary and secondary veins impressed, the tertiary and higher order veins barely impressed, abaxially the primary, secondary, tertiary and higher order veins elevated and terete. Inflorescences an erect pseudolateral multiflorous thyrsoid 3.2 × 5.66 cm, including a peduncle 0.54–0.83 cm long, the dichasial ramifications of the paracladia with secund flowers, divaricately branched from the peduncle apex, borne on the upper foliar axils, the rachis yellowishgreen, the dense dendritic indumentum sparsely intermixed with slightly furrowed more or less stalked glands ca. 0.05 mm long; bracts 3.5–4.2 × 1.8–2.5 mm, spatulate-oblong or rhombic, the margins ciliolate, cilia 1.5–2 mm long, the apex rounded, yellowish-green, the dendritic indumentum sparse adaxially, dense abaxially, whitishtranslucent, persistent in fruit; bracteoles 5.5–7 × 2–2.2 mm, spatulate-obovate, ciliolate at the rounded apex, the cilia becoming less numerous basally in the rest of the margin, 1.5–2 mm long, yellowish-green, the dendritic indumentum dense on both surfaces, persistent in fruit. Flowers 5-merous, sessile. Hypanthia at anthesis 2.5–2.6 × 1.2 mm, free portion of hypanthium 0.9–1 mm long, subcylindric to campanulate, bluntly10-ribbed, yellowish-

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GAMBA & ALMEDA

green, the dendritic indumentum dense, ridged on the inner surface, moderately glandular, the glands sessile and rounded, the torus thickened adaxially, obscurely 10-lobed, densely ciliolate, the trichomes translucent-brown and somewhat flattened, sparsely intermixed with subsessile glands. Calyx open in bud and persistent in fruit, green; tube 0.7 mm long, vaguely undulate, adaxially sparsely and minutely glandular to glabrescent, abaxially with the same vestiture as the hypanthium; lobes obsolete; exterior calyx teeth 0.5 mm long, bluntly tuberculiform, erect to somewhat spreading, inserted at the basal half of the calyx tube and equaling its length. Petals 3.5 × 1.5 mm, subulate to rhombic, the margin entire, the apex bluntly acute, white to translucent-white, glabrous adaxially, abaxially the indumentum resinous and restricted to a median band, each trichome to 0.35 mm long. Stamens 10; filaments 1–1.5 × 0.25 mm, white, glabrous; anther thecae 1.6–1.7 × 0.3 mm, linear-oblong, slightly emarginate at the apex, opening by one dorsally inclined pore 0.15 mm in diameter, white becoming brown with age; connective somewhat darker than the thecae, its prolongation and appendage 0.8–1 mm long, the appendage oblong-subulate, bluntly acute at the apex, conspicuously and densely gland-edged, the glands short-stalked and also present on the dorsal side of the appendage and throughout the connective. Ovary 5-locular, completely inferior, 1.5–1.6 mm long at anthesis, the apical collar 0.5 × 0.8 mm, conic-truncate, sparsely to moderately covered with glandularpuberulent; style 4.8–5 mm long, narrowed distally (i.e. tapering), white, glabrous; stigma truncate to expanded truncate at anthesis. Berries 3.5 × 3 mm when dry, globose-elliptic to globose-obovate, initially green, becoming orange when ripe, the hypanthial indumentum persistent at maturity. Seeds 0.38–0.41 × 0.17–0.18 mm, ovoid, angled, brownish; lateral and antiraphal symmetrical planes ovate, the highest point toward the chalazal side; raphal zone suboblong, nearly as long as the seed and somewhat ventrally expanded; appendage absent but a small protuberance present; individual cells elongate, anticlinal boundaries channeled, undulate, with Ω- and U-type patterns; periclinal walls convex, low-domed to nearly flat, microrelief striate to inconspicuous.

Additional specimens studied:— COLOMBIA. Chocó: (Nóvita), Llanadas, ladera Ndel Cerro Torrá, filo al Wdel Río Surama, Alto del Oso , 1000–1150 m, 22 February 1977, Forero et al. 3223 ( MO, US) ; Llanadas, ladera Ndel Cerro Torrá, filo al Wdel Río Surama, Alto del Oso , 600–900 m, 22 February 1977, Forero et al. 3170 ( COL, MO, US) . Valle: (Dagua), Corregimiento Queremal, P.N.N. Farallones, Sector Alto Anchicayá, Sendero de la quebrada La Riqueza, 3°36’N, 76°53.541’W, 686 m, 10 January 2013, Alvear et al. 1541 ( CAS, COL) .

Illustration:— Fig. 20 .

Common names and documented uses:— None recorded.

Habitat, distribution and ecology:— Local and uncommon in the cloud forests of Valle department in Colombia, in the area known as “Alto Anchicayá”. Also known from Cerro Torrá in the department of Chocó ( Fig. 14 ). These are wet zones which form part of the Chocó, at 600–1150 m.

Phenology:— Collected in flower and fruit in February.

Etymology:— The specific epithet refers to the conspicuous formicarium at the blade base adaxially, a unique character among species of the Octopleura clade and otherwise known in the genus Tococa and a few other species of Miconia in the Miconieae .

Discussion:— This species is readily recognized by the conspicuous formicarium on the foliar bases adaxially. Miconia formicaria is sister to M. bractiflora . Both of these species have conspicuously bracteate multiflorous thyrsoid inflorescences with secund congested flowers. No populations of the latter are known to produce formicaria.

The formicaria in this species can be considered secondary because they are leaf derived. Foliar formicaria are the most common type of ant-domatia among Melastomataceae ( Michelangeli 2010) . Several hypothesis have been proposed for explaining the function of these structures, including protection against herbivory and as a source of nutrients from ants wastes (especially nitrogen), but these remain to be tested for most species. In Michelangeli's (2010) artificial key to myrmecophilous Melastomataceae , this species would be included in Subkey 4 (domatia at the apex of the petiole, or the base of the leaf blade), and would key out in the first couplet (domatia formed by saccate ascidia). The presence of formicaria in this species shows that they might be more common in the tribe Miconieae than expected, and confirms that they have evolved independently across distinct lineages of the Melastomataceae .

Conservation status:— Endangered EN B2ab(iii). Protected inside the Farallones National Park, in a pristine trail of the “Alto Anchicayá”, located in the western slope of the Western Cordillera of the Andes in Valle, Colombia. The flora of this natural zone is related to that of northwestern Ecuador. However, based on current data this species appears to be endemic to Colombia.

SYSTEMATICS OF THE OCTOPLEURA CLADE OF MICONIA

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Figures

FIGURE 14. Distributions of Miconia erikasplundii and M. incerta, M. evanescens, M. formicaria and M. rufibarbis, and M. latidecurrens.

FIGURE 20. Miconia formicaria. A. Habit, showing detail of formicarium at adaxial foliar base. B. Flower. C. Petal, abaxial view. D. Stamen, abaxial view (left), lateral view (right). E. Berry. F. Seed. Based on Almeda et al. 10274, CAS. Drawn by Sean V. Edgerton.

FIGURE 21. Miconia latidecurrens. A. Habit. B. Cauline leaf (abaxial view). C. Flower. D. Stamen, abaxial view (left), lateral view (right). E. Berry, top view (top), lateral view (bottom). F. Seed. Based on: A, B, E, F, McPherson 20808, MO; C, D, Aranda et al. 4226, CAS. Drawn by Sean V. Edgerton.