Myrcia, Parra-O, 2021

Parra-O, Carlos, 2021, Thirteen new species, new records, and a new combination on Colombian Myrtaceae, Phytotaxa 497 (3), pp. 175-210 : 198-199

11. Myrcia samanensis C. Parra-O., sp. nov.

Type:— COLOMBIA. Antioquia: San Luis , “desembocadura de la quebrada San Miguel en la margen izquierda del río Samaná Norte”, 6°2’34.69’’N, 74°55’9.59’’W, 415 m, 18 December 2016 (buds, fl., fr.), S. Hoyos-Gómez, R. Bernal, F. Manrique, S. Bernal & J. Domine 3117 (holotype COL!, isotype HUA!). Figure 13 .

Diagnosis:—This species is similar to Myrcia guianensis ( Aublet 1775: 506–507) De Candolle (1828: 245) , from which it is distinguished by having translucent or whitish hairs (versus usually red hairs in M. guianensis ), blades with 36–48 lateral veins at each side (vs. 15–20), calyx lobes glabrous inside (vs. pubescent), hypanthium not prolonged above the ovary (vs. prolonged), flower disk moderately pubescent (vs. glabrous), and ovary 2-locular (vs. 3-locular).

Description:—Shrub, 1.5–2 m tall; hairs when present 0.1–0.2 mm, simple, drying translucent or whitish; young branches compressed to subcompressed, vinaceous gray to gray, moderately pubescent; old branches terete, yellowish gray to gray, glabrous. Leaf blades narrowly ovate, narrowly oblong or linear, 2.5–7.5 × 0.4–0.8 cm, coriaceous, discolorous, the upper surface glabrous, with slightly raised glandular dots, the lower surface usually scarcely pubescent, sometimes slightly pubescent, with slightly raised glandular dots; apex longly attenuate; base obtuse, sometimes subobtuse; margin entire; midvein flat to slightly convex and slight to moderately pubescent above, markedly convex and scarcely to moderately pubescent below; lateral veins 36–48 pairs, convex and glabrous above, convex and usually glabrous to occasionally scarcely pubescent below, venation joining in an inframarginal vein at 0.1–0.4 mm from margin; petioles 0.5–1.5 mm long, dark vinaceous to blackish above and below, moderately rugose, slight to moderately pubescent, moderate to deeply canaliculate adaxially, axils of petiole with stipule-like, linear or filiform colleters (0.2) 0.5–1.2 (1.5) × 0.1 mm, glabrous. Inflorescences axillary, occasionally terminal, paniculate, 1–2.8 cm long, with 5–13 flowers per panicle, axes compressed, slight to moderately pubescent, vinaceous brown when dry; peduncles 5–12 × 0.3–0.7 mm; bracts elliptic to narrowly elliptic, 2.1–4.2 × 0.7–1 mm, slight to moderately pubescent abaxially, glabrous adaxially, truncate in the base, deciduous after anthesis; bracteoles 1–2, axillary at base of hypanthium, lanceolate, ovate or oblong, 0.5–1.5 × 0.2–0.6 mm, scarcely to moderately pubescent, deciduous after anthesis; flower buds globose, 1.7–2 mm long, 1–1.8 mm in diameter, glabrous to scarcely pubescent, in a subcompressed pedicel 0.5–1.2 × 0.2–0.3 mm, moderately pubescent; calyx lobes 5, depressed ovate to broadly ovate, 0.5–1 × 0.8–1.4 mm, coriaceous, almost glabrous to slightly pubescent outside, glabrous inside, apex obtuse or subobtuse; petals usually 4, white (in scheda), elliptic, broadly ovate or depressed ovate, 1.8–3 × 2.5–3 mm, subcoriaceous, almost glabrous to slightly pubescent outside, glabrous inside, apex obtuse, base truncate, hypanthium 1.3–1.5 mm in diameter, not prolonged above the ovary, moderately pubescent outside, glabrous inside, disk semi-quadrangular, 1.8–2.7 mm, moderately pubescent; style 3.3–3.8 mm long, slight to moderately pubescent at base and half of its extension, scarcely pubescent at the top; stamens 50–60, white (in scheda); filaments 1.8–3.2 mm, anthers globose, 0.1–0.2 mm long, cream (in scheda), with 1 apical gland; ovary 0.8–1 mm in diameter, 2–locular, 1–3 ovules per locule. Fruits ellipsoid, purple (in scheda), blackish when dry, 4–4.5 × 2.5–3 mm, slight to moderately puberulous; seed 1, ellipsoid, 5 × 3 mm, seed coat smooth and somewhat lustrous; embryo myrcioid, with minute light brownish glands.

Distribution, habitat and phenology:— Myrcia samanensis grows in the Samaná Norte river basin in Antioquia Department, and it is part of the rheophytic flora growing in tropical forests associated to such river between 200–800 m elev.; Hoyos-Gómez & Bernal (2018) reported that this species grows specially on rocks at the margins of the Samaná Norte river, in low to moderate flooded areas. Myrcia samanensis seems to be endemic to Colombia. Myrcia samanensis has been collected with buds and flowers in May, June, and December, and with fruits in December.

Conservation:—The conservation status of Myrcia samanensis was assessed by Hoyos-Gómez & Bernal (2018; treated by them as Myrcia sp. nov.) as Critically Endangered (CR) following IUCN Red List criteria ( IUCN 2019). This species has been found only in the basin of the Samaná Norte River, and this natural area is going to be heavily destroyed if a dam for the hydroelectrical plant Porvenir II is built. Hoyos-Gómez & Bernal (2018) estimated the area of occupancy of Myrcia samanensis in the Samaná Norte river basin by 0.61 km 2, and they found that 68% of such area would be flooded if the hydroelectric project is developed. Due to the extremely restricted area of occupancy of Myrcia samanensis and the imminent threat to the natural ecosystem in which it grows, I agree with the conservation status assessing by Hoyos-Gómez & Bernal (2018) for this species according to the IUCN (2019) criteria B2ab(ii, iv).

Etymology:— Myrcia samanensis refers from the type locality in the Samaná Norte River (Antioquia Department) in Colombia, a river with a particular rheophytic ecosystem that has nine exclusive species growing in its basin, where seven of them were recently discovered as new to science ( Bernal et al. 2017; Hoyos-Gómez & Bernal 2018; Posada- Herrera & Almeda 2018).

Affinities:— Myrcia samanensis is very different to all native Colombian species of Myrcia known to date, and it is more similar to Brazilian narrowed leaf forms of Myrcia guianensis that were previously recognized as a separate species of Myrcia guianensis (i.e., Myrcia angustifolia ( Berg 1857 –1859: 135) Niedenzu (1893: 76)); Myrcia angustifolia is considered now as a synonym of Myrcia guianensis ( Lima et al. 2018). The characters that differentiate both species are mentioned in the diagnosis.

Paratypes:— COLOMBIA. Antioquia: San Luis, “vereda San Pablo, río Calderitas , margen izquierda”, 6°2’40’’N, 75°5’14’’W, 800 m, 31 May 2017 (buds, fl.), A . Cogollo, M . Montoya, A . Camargo, J . Correa & L . Zapata 13306 ( COL!, JAUM!); San Carlos , “corregimiento Puerto Garza (Narices), vereda Puerto Garza, río Samaná Norte, margen izquierda, a 15 m aguas debajo de la desembocadura de la quebrada Urón, cerca al Puente de Narices”, 6°12’22’’N, 74°45’34’’W, 200 m, 13 June 2017 (buds), A . Cogollo, M . Montoya, A . Camargo & F . Giraldo 13345 ( COL!, JAUM!); San Francisco , “río Melcocho y río San Francisco”, 5°56’12.05’’N, 75°6’76’’W, s.a., 12 June 2017 (fl.), S . Hoyos- Gómez, J . Domine, R . Bernal & F . Mesa 3196 ( COL!, HUA!) .

Figures

FIGURE 13. Myrcia samanensis. (A) fruiting branch, (B) filiform colleters, (C) flower buds, (D) flower, (E) flower disk with calyx lobes (stamens and petals removed), (F) longitudinal section of hypanthium, (G) embryo. A, B, E–G from the holotype, C from Cogollo et al. 13345, D from Cogollo et al. 13306. Scale bar for B = 0.5 mm, scale bar for C, D, E = 1 mm, scale bar for F = 0.5 mm, scale bar for G = 1 mm.