Meriania escalerensis Rob. Fern., R. Goldenb. & Michelang., 2022

Rocío, Robin Fernandez-Hilario, Gonzáles, Pilar Rojas, Villanueva-Espinoza, Rosa, Lajo, Leticia, Wong Sato, Akira A., Paredes-Burneo, Diego, Pillaca-Huacre, Luis, Michelangeli, Fabián A. & Goldenberg, Renato, 2022, Nine new species and a new country record for Meriania (Melastomataceae) from Peru, Willdenowia 52 (1), pp. 39-74 : 53-56

4. Meriania escalerensis Rob. Fern., R. Goldenb. & Michelang. , sp. nov. – Fig. 9–11 .

Holotype: Peru, Loreto, Prov. Alto Amazonas, Dist. Balsapuerto, Cordillera Escalera, Campamento Cumbre – Alto Cachiyacu , 05°52'02.1"S, 76°46'29.3"W, 1930 m, 22 Sep 2013 (fl.), M. Ríos, T. Mori, D. Neill, L. Torres & C. Vriesendorp 3316 ( AMAZ!; isotypes: F accession no. 2323926 !, USM accession no. 287375 !) .

Diagnosis — A species differing from other congeners by the combination of ferruginous indumentum, calyptrate calyces with circumscissile dehiscence, spreading, deep pink corollas, isomorphic stamens, and stamen connectives with two appendages, one triangular descending dorsobasal appendage and the other blunt ascending dorsal appendage.

Morphological description — Small tree up to 4 m tall; young branches and petioles densely setulose with conic densely roughened trichomes up to 0.3 mm long. Young branches quadrangular, 5–5.5 mm in diam., lacking wings, nodes without interpetiolar flaps. Leaves opposite, isophyllous to slightly anisophyllous. Petioles semiterete, 1.2–2.2 cm long, without projections. Leaf blades coriaceous, 13.3–15.5 × 7.6–8.8 cm, ovate to lanceolate, apex acute to obtuse, base cordate, margin moderately denticulate on distal two-thirds, slightly discolorous; venation acrodromous and basal, with two pairs of secondaries (lateral nerves) and an additional pair of faint submarginal veins running up to leaf apex, tertiary (transversal nerves) 30–41 on each side of primary, percurrent, 1.5–7 mm distant from each other, midvein, secondary and tertiary veins impressed, reticulation barely visible on adaxial surface, midvein and secondary veins salient, tertiary veins prominent and reticulation visible on abaxial surface; adaxial surface flat, golden brown when dry, glabrous to sparsely setulose on veins with similar trichomes to ones on petioles; abaxial surface light golden brown when dry, midvein and secondary veins densely setulose, tertiary veins, reticulations and surface sparsely to moderately setulose, with trichomes similar to ones on petioles, denser on veins. Inflorescences terminal panicles, erect, c. 22 × 14 cm, submultiflorous or multiflorous; axis and peduncle densely setulose with trichomes similar to ones on terminal twigs, longer (up to 0.75 mm long) on nodes. Peduncle 4.5–7 cm long, quadrangular. Main axis 15.7–16.5 cm, quadrangular. Paraclades in 6 pairs, proximal 9–10 cm long, distal 2.2–2.5 cm long; flowers in regular dichasia at ends of branchlets. Bracts foliaceous, persistent or caducous, 2.9 × 0.9 cm, elliptic, petioles 7.5–8 mm long, indumentum denser than ones on leaves. Bracteoles not seen (probably early caducous). Flowers 5-merous, erect, with spreading corollas. Pedicels 2.5–3 mm long, ferruginous, densely setulose with trichomes similar to ones on peduncle and axis up to 0.3 mm long. Hypanthium c. 4.5 × 7 mm, campanulate, ferruginous, outer surface densely setulose with trichomes similar to ones on pedicels, inner surface glabrous; torus glabrous. Calyx with circumscissile dehiscence, ferruginous, outer surface densely setulose with trichomes similar to ones on pedicels, inner surface glabrous; calyx lobes fused, forming a calyptra, 8–9.5 mm long, conic and acuminate, without dorsal projections. Petals c. 21 × 14 mm, c. 2.5 mm wide at base, obovate, apex rounded, margin entire, pink, glabrous. Stamens 10, isomorphic, all bent to one side of flower giving flower a zygomorphic appearance; filaments c. 8.5 mm long, pink, flat, glabrous; connectives not prolonged below thecae, light purple in distal half of thecae, cream in proximal half of thecae, with two appendages, one descending dorsobasal, c. 3.75 mm long, triangular, cream, other ascending dorsal appendage, c. 0.75 mm long, blunt, cream, 3–3.5 mm from tip of descending dorsobasal appendage; anthers c. 7.5 mm long, lanceolate, magenta on apex and cream to base, glabrous, straight, opening by one dorsally inclined pore, thecae surface corrugated. Ovary 5-locular, superior, c. 5 × 4–4.5 mm, ovate and 10-lobed, with an apical ring of 10 teeth, 1 mm long, pink, c. 1 mm exceeding hypanthium length, glabrous; style c. 10 mm long, pink, glabrous, slightly incurved at apex and opposite anthers at anthesis; stigma punctiform and minutely papillate, c. 0.4 mm wide, whitish. Fruits and seeds not seen.

Phenology — Flowering occurs in September.

Distribution and ecology — Meriania escalerensis is probably endemic to elfin forests on high-elevation summits of the Cordillera Escalera (Loreto-San Martín border), on a sandstone substrate above 1950 m. The Cordillera Escalera is one of the “sub-Andean cordilleras” (Andean Tepuis sensu Neill & al. 2014) to the east of the E Andes. Common tree and shrub genera in the area include Clusia L. ( Clusiaceae ), Weinmannia L. ( Cunoniaceae ), Ocotea Aubl. and Persea Mill. ( Lauraceae ), Cybianthus Mart. ( Primulaceae ) and Palicourea Aubl. and Psychotria L. ( Rubiaceae ) ( Neill & al. 2014).

Conservation status — Meriania escalerensis is known from a single collection from the Cordillera Escalera. Currently, the main threats facing the Cordillera Escalera are the lack of a legal designation to protect it, the Moyobamba-Balsapuerto highway project and gas and petroleum exploration and production (for more details see Pitman & al. 2014). Therefore, following IUCN (2012, 2019) guidelines and based on an estimated area of occupancy of 4 km 2, we recommend the category Critically Endangered CR B 2ab(ii) for this species.

Etymology — The specific epithet refers to the type locality “Cordillera Escalera”.

Discussion — Meriania escalerensis may be related to the Meriania “brachycera ” group ( Mendoza-Cifuentes & Fernández-Alonso 2012), based on the presence of ferruginous indumentum, calyptrate calyx with circumscissile dehiscence, spreading corollas, and stamen connectives with ascending dorsal appendages. Within this group the species that are most similar to M. escalerensis are M. haemantha (Planch. & Linden) Humberto Mend. & Fern. Alonso ( Colombia and Venezuela), M. sararensis Humberto Mend. & Fern. Alonso ( Colombia) and M. yalconensis Humberto Mend. & Fern. Alonso ( Colombia). However, M. escalerensis differs from the first by its leaf blades 13.3–15.5 × 7.6–8.8 cm (vs 11–31 × 6.5–22 cm), 5-merous flowers [vs 6–7(–9)-merous] and calyces 8–9.5 mm long (vs 9–19 mm); it differs from the second by its petioles 1.2–2.2 cm long (vs 2.7–3.8 cm), erect inflorescences (vs pendulous) and hypanthia and calyces with similar trichomes, up to 0.3 mm (vs clearly longer trichomes on the calyces, up to 1 mm); and it differs from the third by its 30–41 tertiary veins (vs 50–65), 5-merous flowers (vs 7- or 8-merous) and petals c. 21 mm long (vs 29–42 mm).

The only Peruvian species with calyptrate calyces are Meriania acida and M. tomentosa , the former endemic to N Peru and the latter distributed from Venezuela to Bolivia. Nevertheless, M. acida and M. tomentosa have calyces with irregular dehiscence and campanulate, reddish orange corollas, whereas M. escalerensis has calyces with circumscissile dehiscence and spreading, deep pink corollas. In addition, M. acida has leaf blades with acute bases and M. tomentosa with obtuse to rounded bases (vs cordate in M. escalerensis ).

Currently, there are two species that grow in the sub-Andean Cordilleras of N Peru, Meriania escalerensis in the Cordillera Escalera (Loreto-San Martín border) and M. microflora Rob. Fern. & al. on the Cerros Kampankis (Amazonas-Loreto border). The two type localities are approximately 220 km apart and are dominated by oligotrophic sandstone substrates ( Pitman & al. 2012; Pitman & al. 2014). Although M. escalerensis and M. microflora grow in similar habitats, they are quite different. The two species are easily distinguished by the petiole projections (absent in M. escalerensis vs present in M. microflora ), the length and colour of the petals (c. 21 mm and deep pink vs 4–4.5 mm and white) and the shape of the stamens (isomorphic vs strongly dimorphic).

Figures

Fig. 9. Distribution map of Meriania callosa, M. escalerensis and M. zunacensis.

Fig. 10. Meriania escalerensis – A: terminal fertile branch with inflorescence; B: detail of abaxial leaf surface; C: detail of ovary apex; D: flower bud, lateral view; E: petal; F: stamen, lateral view; G: hypanthium, lateral view; H: longitudinal section of flower with petals and stamens removed. – A–H from M. Ríos & al. 3316. – Drawing by Leticia Lajo (E).

Fig. 11. Meriania escalerensis – A: terminal fertile branch with inflorescence; B: flower at anthesis, apical view. – A–B from M. Ríos & al. 3316. – Photographs by Luis Torres.