Miconia laxivenula (Wurdack) 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: COLOMBIA. Comisaría del Putumayo: Umbría, 0°54’N, 76°10’W, 325 m, October–November 1930, Klug 1816 (holotype: US!; isotypes: F!, MO!, NY!).

Description: Shrub or small tree 1.5–5(–9) m tall, main stem laxly and poorly branched, bark green to green-brownish, smooth. Upper internodes compressed-rounded, (1.9–)3.2–6.9 cm long, cauline nodes terete, nodal line absent. Indumentum on branchlets, petioles, primary and secondary leaf veins abaxially, inflorescence axes, bracts, bracteoles, pedicels when present, hypanthia, calyx lobes and calyx teeth sparsely composed of caducous amorphous lepidote trichomes <0.1 mm long with only partially fused radii that superficially resemble minute glandular scales. Leaves of each pair commonly isophyllous, occasionally slightly anisophyllous in size; the semiterete petiole (1–)1.5–3 cm long, moderately canaliculate abaxially; blades 9–29 × 3.4–13.5(–14) cm, elliptic to oblong-elliptic, or elliptic to elliptic-obovate, the base acute, commonly but not exclusively decurrent on the petiole, the margin entire to obscurely crenulate, the apex acute to bluntly short-acuminate, chartaceous; mature leaves adaxially with surface, primary, secondary, tertiary and higher order veins glabrous; abaxial surface occasionally to rarely flushed red-purple, completely glabrous or glabrescent to sparsely and distantly puncticulate, the points superficially black and consisting of resinous short-stalked glands with thin-walled elongate heads, the tertiary and higher order veins glabrous; 5-plinerved, including the tenuous marginals, innermost pair of secondary veins diverging from the primary vein 1–1.5 cm above the base, areolae 2–3 mm, adaxially the primary and secondary veins impressed, the tertiary and higher order veins slightly impressed to flat, abaxially the primary and secondary veins elevated and terete, the tertiary and higher order veins slightly elevated. Inflorescences a pseudolateral multiflorous dithyrsoid 7–11 cm long, including a peduncle <1 cm long or sessile, divaricately and highly branched from the peduncle apex, with somewhat deflexed lower most branches, when sessile bifurcate or trifurcate from the base, each furcation with the same architecture as the pedunculate dithyrsoid, borne in the upper leafy nodes, the rachis red-purplish; bracts and bracteoles 0.5–1 × 0.25 mm, the bracts triangular-concave, the bracteoles subulate, green-reddish, glabrescent on both surfaces, persistent to tardily deciduous in fruit. Flowers 4-(5-) merous sessile or subsessile, the pedicels 0.1–0.2 mm long when present. Hypanthia at anthesis 1.7–2 × 1.2–1.3 mm, free portion of hypanthium 0.6–0.8 mm long, globose to urceolate, becoming dorso-ventrally compressed in fruit, bluntly 8-(10-)ribbed, green-whitish, ridged on the inner surface, sparsely beset with conspicuous brown rounded glands, the torus adaxially minutely glandular. Calyx open in bud and persistent in fruit, green; tube 0.2–0.3(–0.5) mm long, with the same vestiture as the torus adaxially and as the hypanthium abaxially; lobes 0.1 × 0.75–0.85 mm, or if obsolete then just the tube present, depressed-rounded, the margin vaguely and obscurely undulate, the apex obtuse; exterior calyx teeth 0.2 mm long, minutely depressed-rounded, inserted at the base of the calyx lobes or tube, not projecting beyond the lobes but covering their entire dorsal surface. Petals 2.5–3.5 × 0.5–1 mm, lanceolate-triangular, the margin entire, the apex bluntly acute, white to translucent white, glabrous, reflexed at anthesis. Stamens 8; filaments 1.2–2 × 0.25 mm, white-yellowish, glabrous; anther thecae 1–1.25 × 0.3–0.4 mm, oblong-obovate, truncate to emarginate at the apex, opening by two dorsally inclined pores 0.1–0.15 mm in diameter, white-yellowish; connective pale yellow, its prolongation and appendage (0.5–)0.6–0.8 mm long, the appendage oblong-deltoid or orbicular, obtuse or rounded-truncate at the apex, copiously and conspicuously gland-edged, the glands stalked and apically rounded. Ovary 4-locular, 3/4 inferior, 1.3–1.5(–1.7) mm long at anthesis, the apical collar 0.3–0.4 × 0.17–0.19 mm, conic, conspicuously glandular-puberulent; style 3–3.3 mm long, narrowed distally (i.e. tapering), white, glabrous; stigma expanded truncate to capitellate. Berries 2–2.5 × 3–3.8 mm when dry, globose-oblate, white or orange when fully ripe, the hypanthium indumentum persistent at maturity. Seeds 0.44–0.5 × 0.16–0.19 mm, typically pyramidal, occasionally ovoid and angled, brownish; lateral and antiraphal symmetrical planes triangular, the highest point toward the chalazal side; raphal zone suboblong to sublinear, ca. 90% the length of the seed, somewhat ventrally expanded toward the micropyle or from the chalazal side to the micropyle; appendage absent but a small protuberance present; individual cells elongate, anticlinal boundaries channeled, undulate, with [Omega] and U-type patterns; periclinal walls convex, low-domed to nearly flat, microrelief verrucose to somewhat striate.

Common names: Ecuador: “cayapa”, for curing cramps and epilepsy (Barfod et al. 48173, MO!); “chicnul” (Quelal et al. 539, MO!); “engal chignul”, for making traps (Tipaz et al. 1445, MO!); “uvitilla” (Quelal et al. 143, MO!); “payatzi" (Vargas & Cerda 548, MO!). The first common name is used by the Cayapa Amerindian community; the next three common names are used by the Awá ethnic community. Ecuador: “cayapa”, for curing cramps and epilepsy (Barfod et al. 48173, MO!); “chicnul” (Quelal et al. 539, MO!); “engal chignul”, for making traps (Tipaz et al. 1445, MO!); “uvitilla” (Quelal et al. 143, MO!); “payatzi" (Vargas & Cerda 548, MO!). The first common name is used by the Cayapa Amerindian community; the next three common names are used by the Awá ethnic community.

Habitat and Distribution: Locally common in primary or secondary lowland rain forests and montane forests, growing on flat areas or steep slopes, commonly in the understory and near streams, from southern Nicaragua through southern Central America, to Colombia, Ecuador and Perú , at 42–1200(–1900) m. In Nicaragua it is only known from the Reserva Natural Indio-Maíz; it occurs throughout Costa Rica and in Panama it is known from central areas of the country. In South America the distribution is disjunct. In Colombia it is only known from the southern departments of Nariño and Putumayo, and it occurs throughout Ecuador to northern Perú. Manakins, Tanagers, Thrushes, the orange-billed Sparrows (Arremon aurantiirostris) and Myadestes melanopshave been reported to feed on M. laxivenula berries in a Costa Rican premontane wet forest (Stiles & Rosselli1993).

Phenology: Collected in flower and fruit throughout the year, but only flowering material has been collected in March.

Etymology: The specific epithet refers to the lax (loose) reticulation on the abaxial surfaces of leaves.

Taxonomy and Systematics: Miconia laxivenula has lax foliar reticulation in which the areoles are conspicuously bigger than in other species of the Octopleura clade (2–3 mm vs. commonly <2 mm) and its leaves are commonly narrowly decurrent on the petiole. In the protologue Wurdack (1973a) recognized M. sessilis as the closest relative of M. laxivenula, which is confirmed on the basis of molecular data showing that M. laxivenula is sister to M. sessilis . Both have a basal position among some species within the Variabilis subclade, including M. magnifoliaand allies. Morphologically M. sessilis has similar lax venule reticulation (areoles 3–5 mm) and 4-merous flowers, but its leaf blades are long decurrent at the base (leaves sessile), it has more prominent foliar plinervation (innermost pair of secondaries diverging 3–5 cm vs. 1–1.5 cm above the base), and the petals are densely puberulent abaxially (vs. glabrous). Miconia variabilis is similar in appearance and inflorescence architecture but differs in the much denser foliar venule reticulation (areoles ca. 0.2 mm), densely puberulent vegetative and floral indumentum, and 5-merous flowers. The flowers in M. laxivenula are predominantly 4-merous. One specimen from the province of Coclé in Panama (Hammel s.n., MO-2686219!) has fruits that are uniformly 10-costate (and thus 5-merous flowers), a rare and unusual variant. Wurdack (1973a) suspected that O. robusta (Triana) Cogn. fma. glabrata Mgf., which was described as a glabrous population from eastern Ecuador (Pacapaca region, apparently in the province of Pastaza), is the same taxon as M. laxivenula. The holotype chosen by Wurdack was previously determined as O. robusta fma. glabrata Mgf., but it was not cited by Markgraf (1941) in the protologue. The only specimen that Markgraf (1941) based this form on (Schultze-Rhonhof 2717) was not seen; all the Pastaza specimens of M. laxivenula studied have 4-merous flowers and were not glabrous, but covered with the squamate-amorphous indumentum that characterizes this species. Markgraf (1941) did not specify the merosity of the specimen he cited, and no records from that region (locality details are not clear) were seen. Specimens of M. variabilis examined for this study have 5-merous flowers, and those from the province of Pastaza had the normal M. variabilis indumentum. The taxon described by Markgraf (1941) will probably remain unknown based on available evidence. The only specimen cited by Markgraf was probably deposited in B along with the other Schultze collections. It was destroyed during the Second World War. The lax foliar reticulation and squamate-amorphous indumentum of M. laxivenula are consistent throughout its geographic range. However, two distinguishable morphological variants have come to light in the course of this study. The type of this species was collected in Colombia (Putumayo) and in accord with South American specimens, has leaves that are elliptic to oblong-elliptic with the base acute and not decurrent along the petiole, or only slightly so. The abaxial leaf surfaces are completely glabrous, and the berries are orange at maturity, which can change to purple-black according to some specimen labels (Acosta-Solís 12215, F!). These populations are known from Colombia (Nariño, Putumayo), Ecuador (Esmeraldas, Napo, Pastaza, and Sucumbíos) and Perú (Huánuco), at 250–1200 m. The second morphological variant includes specimens with leaves that are elliptic to elliptic-obovate. The blade base is acute and conspicuously decurrent on part of the petiole, the abaxial leaf surfaces are black-puncticulate (with minute resinous trichomes), and the berries are white at maturity. Populations with these characteristics have been collected more abundantly than those that conform to type material. These populations are found where the species has been collected in Mesoamerica, and also in Ecuador (Carchi, Cotopaxi, El Oro, Esmeraldas, Pichincha, and Morona-Santiago) and Perú (departments of Amazonas, and San Martín), at 42–975(–1900) m. The floral morphology and measurements of these two morphological variants are consistent, as are the characters mentioned above which supports the view that they belong to the same taxon. The fact that they co-occur in the province of Esmeraldas in Ecuador would prohibit recognizing them as subspecies, since there is no geograp

Conservation Status: This species would be considered Endangered EN B2ab(iii) based on IUCN criteria (AOO). However, it occurs in many protected areas throughout its range, which warrants a status of Least Concern LC. Protected in Costa Rica in the Monteverde Biological Reserve (Alajuela); in the Guanacaste National Park (Guanacaste); in La Selva Biological Station and the Braulio Carrillo National Park (Heredia, the latter also in Limón); in the Golfo Dulce Forest Reserve and in the Corcovado National Park (Puntarenas). In Ecuador it is protected in the Awá Indigenous Reserve (Carchi and Esmeraldas); in the Cotacachi-Cayapas Ecological Reserve (Esmeraldas); and in the ENDESA Forest Reserve (Pichincha). In Nicaragua it is protected in the Indio-Maíz Reserve (Río San Juan).

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