Macrocentrum andinum Michelang. & R.Goldenb., 2018

Michelangeli, Fabián A. & Goldenberg, Renato, 2018, New and noteworthy Melastomataceae from the Yanachaga-Chemillén National Park and surrounding areas in Oxapampa, Pasco, Peru, Phytotaxa 374 (3), pp. 185-210 : 187-190

1. Macrocentrum andinum Michelang. & R.Goldenb. sp. nov. ( Figure 1 )

Diagnosis: —Differs from Macrocentrum steyermarkii Wurdack (1967a: 267) by the epiphytic habit (vs. epipetric), stem trichomes up to 3 mm long (vs. absent or up to 1.2 mm long), leaves serrulate in the distal apex (vs. entire or ciliolate), and glandular pubescent on both surfaces (vs. glabrous).

Type:— PERU. Pasco: Province of Oxapampa, Distrito Palcazú, Parque Nacional Yanachaga-Chemillén , Quebrada David , 10°23’23”S 75°17’07”W, 576 m, 28 May 2011 (fl, fr), R. Vásquez, M. Villalba & C. Mateo 37403 (holotype NY!; isotypes HOXA, HUT, MO!, MOL, USM) .

Epiphytic herb 7–20 cm tall. The stems with adventitious roots, especially towards the base where devoid of leaves; towards the apex slightly quadrangular, sparsely pubescent, the trichomes 1.5–2.5 mm long, simple and glandular, mostly along the ridges of the internodes, but also on the nodes and in between the ridges, the internodes with an interpetiolar line and minute (<0.1 mm long) sessile dark glands. Leaves anisophyllous, larger leaves oblanceolate to obovate, petioles 3–10(–13) mm long; blades 12–26 × 3.4–7.5(–9) mm, base acute, apex bluntly acute, margin entire in the proximal half and crenulate, ciliate in the distal half, the trichomes on each tooth simple, glandular, up to 3 mm long, abaxial surface very sparsely glandular-setulose, tricomes 2.2–3 mm long, densely white pustulate and with sparse dark sessile glands ca. 1 mm long, 1-nerved, adaxial surface sparsely glandular-setulose, trichomes 1.8–3 mm long; smaller leaves sometimes absent, if present, with the same shape and indumentum as the larger leaves, petioles 1.5–3.5 mm long, blades 3.5–6(–9) × 2.2–4.2 mm. Inflorescences solitary or in pairs in the upper leaf axils, pedicels 5–8.5 mm long, quadrangular and winged, sparsely glandular-setulose, trichomes up to 2.5 mm long. Bracteoles caducous, up to 1.8 mm long, subulate to spatulate, glabrous or with a few glandular trichomes up to 0.5 mm long. Flowers 4-merous. Hypanthium 2.6–3.1 mm long, broadly campanulate, sparsely glandular-setose, torus glabrous. Calyx tube 0.3–0.45 mm long, sepals internal laminae 0.9–1.25 mm long, rounded, margin slightly irregular and with sessile glands slightly imbricate, sepals external projections absent. Petals white, oblong to oblong-lanceolate, 5–6 × 2.5 mm, apex broadly acute; stamens isomorphic, glabrous, filaments 3–3.2 mm long, thecae 2.2 mm long, connective not prolonged, but with a dorsal subulate tooth 0.7–1 mm long. Ovary 4/5 inferior, 3-locular, apex truncate, glabrous; style ca. 5.7 mm long, glabrous, stigma punctiform. Fruits capsular, apically dehiscent, 8-costate, the sepals persistent.

Paratype:— PERU. Pasco: Province of Oxapampa, Distrito Palcazú, Parque Nacional Yanachaga-Chemillén, Quebrada Paujil, 10°19’26”S, 75°15’49”W, 399 m, 23 October 2014 (fr), R. Vásquez et al. 39321 ( HOXA!, MO!, USM!).

Distribution, ecology, and phenology:— Macrocentrum andinum is known from only two specimens at 399–576 m elev., growing as a low epiphyte along two small creeks, both tributaries of the Iscozacín River in the eastern portion of the Yanachaga-Chemillén National Park ( Figure 2 ). Flowers and fruits present in October.

Conservation Status:— Macrocentrum andinum is known from only two localities less than 5 km away, both of them inside the National Park. Although we would wish to recommend it to be considered as Critically Endangered, at this point it is probably best considered as Data Deficient (DD) ( IUCN 2001; IUCN Standards and Petitions Subcommittee 2017).

Etymology:—The specific epithet refers to the fact that this is the first species of Macrocentrum described from the foothills of the Andes.

Comments:— Macrocentrum andinum closely resembles M. steyermarkii due to its anysophyllous leaves with the larger one at each node oblanceolate to obovate, and four-merous flowers on long pedicels. However, it differs from it by the presence of longer glandular trichomes on the stem and the leaves serrulate towards the apex and pubescent on both surfaces (vs. leaves entire and glabrous). Macrocentrum andinum also resembles M. minus Gleason in Steyermark (1952: 432), but the latter has sessile flowers and the upper leaf surface trichomes are confined to the outer third, while they are spread throughout in the former.

As indicated above, Macrocentrum is a genus mostly restricted to the Guiana Shield, with one species found in the Coastal Cordillera of Venezuela (Wurdack 1973; Berry et al. 2001). A few specimens that perfectly match the type and other specimens of M. yaracuyense Wurdack (1969 [1970]: 59) have also been collected in the Cordillera del Condor in Southern Ecuador and in the Marañon valley in Northern Peru. However, M. andinum does not resemble M. yaracuyense (or the closely related M. cristatum ( de Candolle 1828: 113) Triana (1871: 79)) .

Figures

FIGURE 1. Macrocentrum andinum. A. Fertile branch with fruits. B. Leaves, adaxial surface. C. Flower bud. D. Petal, adaxial surface. E. Flower, longitudinal section, with petals and stamens removed; details of calyx and calyx margin. F. Stamen, antesepalous from left to right, lateral view, dorsal view, ventral view, detail of stamen apex. G. Capsule, lateral view. H. Capsule, longitudinal section. A–H from Vasquez et al. 37403 (NY).

FIGURE 2. Distribution of Macrocentrum andinum and Meriania rubriflora