Meliosma chanchamayensis Rob.Fern. & Reynel, 2022

Fernandez-Hilario, Robin & Reynel, Carlos, 2022, Two new species of Meliosma (Sabiaceae) from the premontane and montane forests of the Selva Central of Peru, Phytotaxa 559 (1), pp. 45-54 : 46-47

1. Meliosma chanchamayensis Rob.Fern. & Reynel , sp. nov. ( Figures 1–2 )

Diagnosis:— Meliosma chanchamayensis is more closely related to M. wurdackii Cuatrecasas (1988: 493) but differs by the width of leaf blades [(4.0-)5.0– 7.2 cm vs. 9.5–13 cm], indumentum on abaxial leaf blades (glabrous vs. tomentulose), pedicels length (0.5–0.8 mm vs. sessile), and sepals length (0.71–0.90 mm vs 1.2–1.5 mm). Additionally, it differs from other congeneric by the combination of elliptic to sometimes slightly obovate leaf blades, sepals 5, 0.71–0.90 mm long, glabrous outer petals 1.34–1.86 mm long, apically papillate and bifid inner petals 0.89–0.91 mm long, inner petals shorter than the filaments, and drupes 1.6–1.7 × 1.5–1.6 cm.

Type:— PERU. Junín: Prov. Chanchamayo, Dist. San Ramón, La Promisoria , 11°05′ S, 75°23′ W [11°03′20″ S, 75°24′40″ W], 1070–1200 m, 26 Nov. 1998 (fl.), T. D. Pennington & A. Daza 16505 (holotype MOL! [barcodes 000110 – 1/2, 000111 – 2/2]; isotype E! [barcode E00189854 ]) .

Tree up to 25 m tall and 50 cm DBH. Terminal branchlets terete, 4.5–5 mm diam., glabrous and lenticellate. Leaves alternate, rarely subverticillate; petioles terete, (1.2-) 1.6–2.6 cm long, slightly basally swollen (pulvinus-like) and inflexed in fresh, glabrous, dark brown at the apex and black at the base when dry; leaf blades coriaceous, (14.0-)18.9–27.7 × (4.0-)5.0– 7.2 cm, elliptic, sometimes slightly obovate, apex acuminate, base acute to cuneate, margin entire, slightly discolorous; venation brochidodromous, with 17–22 secondary veins, 3–19 mm distant from each other, central secondary veins with (41-)50–71°, intersecondary veins present or absent; adaxial surface with the midvein and secondary veins impressed, the reticulation barely visible; abaxial surface with the midvein salient, secondary veins prominent and the reticulation visible; adaxial surface flat, glabrous, dark brown when dry; abaxial surface glabrous, light brown when dry. Inflorescence a terminal or axillar erect panicle, ca. 24.7 × 8.5 cm, multiflorous, branched 2- times, peduncle and axes sparsely to densely pubescent; bracts not seen (probably early caducous); bracteoles scalelike, margin ciliate, ca. 0.65–0.75 mm long. Flowers pale cream in fresh; pedicels 0.5–0.8 mm long, densely pubescent. Sepals 5, subequal. 0.71–0.90 × 0.68–0.90 mm, broadly ovate, margin ciliate. Petals 5; outer petals 3, 1.34–1.86 mm long, orbicular to widely ovate, margin entire, glabrous; inner petals 2, 0.89–0.91 mm long, shorter than the filaments, bifid, basally adnate to the stamens, each lobe ovate and apically obtuse 0.29–0.38 mm long, apically papillate. Stamens 2, 1.59–1.61 mm long; filaments 0.95–1.00 mm long; anthers 0.55–0.66 × 1.05 mm, thecae subtended by connective tissue; staminodes 3, 0.81–1 mm long, irregular and forming a mass that completely covers the ovary, opposite to outer petals and basally adnate to them. Ovary 0.75–0.85 mm long, ovoid, glabrous, with an irregular dentate-ciliate cupuliform disk; style 0.12–0.22 mm long; stigma punctiform. Infructescence erect, ca. 28 × 12 cm, peduncle and axes glabrescent. Drupes 1.6–1.7 × 1.5–1.6 cm, subspherical to slightly obovoid, black when dry. Seeds not seen.

Distribution and habitat:— Meliosma chanchamayensis is a Peruvian tree endemic known from a single locality in the premontane forests of the District of San Ramón (Junín), on moderate to strong slopes, here it occurs in mature rainforests between 1000–1200 m.

Phenology:— Flowering in November, and fruiting in February and November.

Etymology:— The specific epithet refers to the Chanchamayo valley of Junín, where the only population of this new species was collected.

Conservation status:— Meliosma chanchamayensis is known from three collections from San Ramón district of the Chanchamayo Province (Department of Junín). Currently, the mature forests in the San Ramón district are being destroyed due to the agricultural and urban expansion ( Reynel & León 1989; Horgan 2009). Although Junín is a relatively well-explored region (see Antón & Reynel 2004; Marcelo-Peña & Reynel 2014; Giacomotti et al. 2021), several endemic species have been discovered in recent years, e.g.: Dicliptera mercedesiae Villanueva et al. (2021: 37) , Coussapoa peruviana C.C.Berg in Berg & Ulloa Ulloa (2014: 14) and Magnolia Juninensis Arroyo (2014: 220) . Following IUCN (2012, 2019) guidelines and based on estimated area of occupancy of 8 km 2, we recommended the category Critically Endangered CR B2ab(iii) for this species.

Discussion:— Vegetatively M. chanchamayensis most closely resembles M. glabrata ( Liebmann 1850: 71) Urban (1895: 212) ( Mexico to Peru), M. gracilis Cornejo & Bonifaz in Cornejo (2008b: 96) ( Ecuador) and M. occidentalis Cuatrecasas (1948 [1949]: 217) ( Costa Rica to Ecuador). Nevertheless, M. chanchamayensis is easily distinguished from these species by its bifid inner petals (vs. linear, ligulate or lanceolate in the other species) and inner petals shorter than filaments (vs. longer than stamens). Additionally, M. chanchamayensis differs from the M. glabrata by its outer petals 1.34–1.86 mm long (vs. 2.2–2.4 mm), and drupes 1.6–1.7 × 1.5–1.6 cm (vs. 2.3–2.6 × 1.8–2 cm); also, M. chanchamayensis differs from the M. gracilis by its petioles (1.2-) 1.6–2.6 cm long (vs. 0.5–1.8 cm in M. gracilis ), pedicels 0.5–0.8 mm long (vs. 1–2 mm), and infructescence erect (vs. pendulous). Finally, M. chanchamayensis differs from M. occidentalis by its leaf blades with 17–22 secondary veins (vs. 10–18), abaxial leaf blades glabrous (vs. moderately puberulent), and drupes 1.6–1.7 × 1.5–1.6 cm (vs. 2.4–2.8 × 1.9–2.2 cm).

Establishing relationships between Meliosma species is complicated because some species have been published from only fruiting material and even unicates [e.g.: M. littlei Cuatrecasas (1959: 172) , M. youngii Gentry (1992: 157) ]. In addition, the complex configuration of the flowers has caused that many descriptions are not sufficiently detailed. Probably within the Andean and Amazonian Meliosma species, M. chanchamayensis is more closely related to M. wurdackii Cuatrec. ( Peru and Bolivia) but differs by the width of leaf blades [(4.0-)5.0– 7.2 cm vs. 9.5–13 cm], indumentum on abaxial leaf blades (glabrous vs. tomentulose), pedicels length (0.5–0.8 mm vs. sessile), and sepal length (0.71–0.90 mm vs 1.2–1.5 mm).

Paratypes:— PERU. Junín: Prov. Chanchamayo. Dist. San Ramón, La Promisoria, 11°05′ S, 75°23′ W [11°03′20″ S, 75°24′40″ W], 1070–1200 m, 26 Nov. 1998 (fr.), T.D. Pennington & A. Daza 16506 ( MOL!), track to Pampa Hermosa, La Promisoria valley , 11°03′ S, 75°24′ W, 1000 m, 11 Feb. 2003 (fr.), T.D. Pennington & A. Daza 17518 ( E!, MOL!) ,

Figures

FIGURE 1. Meliosma chanchamayensis. A. Terminal sterile branch. B. Infructescence. C. Inflorescence, and detail of flowers at ends of inflorescence branchlet. D. Flower bud. E. Mature fruit. F. Flower bud with two petals and staminodes removed. G. Pistil. H. Sepal. I. Petal with adnate staminode. J. Stamen with adnate inner petal, frontal and posterior view. J. Inner petal. L. Staminode.A, C, D and F-L from T.D. Pennington & A. Daza 16505; B and E from T.D. Pennington & A. Daza 16506.

FIGURE 2. Distribution map of Meliosma chanchamayensis and Meliosma dazae.