Myrcia ascendens M.F.Santos, 2015

Santos, Matheus F., Lucas, Eve & Sano, Paulo T., 2015, Five new South American species of Myrcia s. l. (Myrtaceae), Phytotaxa 234 (2), pp. 159-171 : 160-162

1. Myrcia ascendens M.F.Santos , sp. nov. ( Figs. 1 , 2 )

Myrcia ascendens is related to Myrcia densa (De Candolle 1828: 257) Sobral (2006: 136) , but differs in having slender lateral branches almost vertically inclined (versus thicker branches with inclination variable), the rare presence of cataphyll scars (vs. present at least at the basal internode), internodes 0.2–1.0 cm long (vs. 0.5–4.5 cm), lateral veins 1 mm apart (vs. 1–3 mm) and marginal vein 0.2 mm from the margin (vs. 5–10 mm).

Type:— BRAZIL. Bahia: Mun. Mucugê, Serra de São Pedro, 17 December 1984 (fl.), G.P. Lewis CFCR 7074 (holotype SPF!, isotypes K!, NY!, RB!).

Shrub to tree, 1– 3 m. Epidermal peeling absent in the immature parts; trichome brown to light brown, 0.1–0.3 mm long, dibrachiate. Twig when immature greenish to reddish, flattened, keeled, pubescent or puberulent; mature twig greyish, cylindrical, cortex slightly cracked, glabrous; branching monopodial, 2–3 branches per node, epidermal protrusion absent at the internodes, internode 0.2–1.0 cm long; cataphyll foliaceous, 1–2 × 1 mm, rarely present, early deciduous, free, lanceolate, externally puberulent, internally glabrous; branch with a single apical bud, pubescent. Leaf concolorous, chartaceous, blade 0.5–1.6 × 0.1–0.5 cm, narrowly elliptic or oblanceolate, apex acute, obtuse or rounded, base narrowly cuneate or cuneate, margin revolute at the base, secondary veins ca. 1 mm apart, held at an angle of 45 o relative to the midvein, marginal vein 0.2 mm from the margin, tertiary veins inconspicuous; immature adaxial surface with scattered trichomes, glabrous at maturity, midvein flat along the entire length, secondary veins inconspicuous, pellucid dots conspicuous, more than 15 per mm 2; immature abaxial surface puberulent or with scattered trichomes, glabrescent to glabrous at maturity, midvein prominent, secondary veins inconspicuous (sometimes slightly prominent), pellucid dots conspicuous, more than 15 per mm 2; petiole 1–3 × 1 mm, canaliculate to semicylindrical, puberulent or with scattered trichomes when immature, glabrous at maturity. Panicle 1–2 × 1–2 cm, umbelliform, terminal axillary or subterminal, 10–25 flowers, rachis puberulent, 1–2 branching at the base (sometimes with a central vegetative branch), first internode of central rachis 1 mm wide, flattened, distal internodes flattened, opposite branching, three times per node, epidermal protrusion in the node usually present. Bract 1.2–2.4 × 0.4–0.6 mm, deciduous, lanceolate or ovate, concave, apex acuminate, base truncate, adaxial and abaxial surfaces puberulent. Pedicel 0–0.6 mm long, cylindrical, puberulent. Bracteole 1.2 × 0.4 mm, deciduous, lanceolate, concave, apex acuminate, base truncate, adaxial and abaxial surfaces puberulent. Floral bud 2 × 1 mm, turbinate. Hypanthium extending 0.6–0.8 mm above the summit of the ovary, not tearing at anthesis, externally pubescent or puberulent, glabrescent towards the apex, conspicuous pellucid dots covering the whole surface, internally glabrous; calyx 4–5-merous, lobes 0.6–1.0 × 0.6–1.0 mm, distinct from the hypanthium, external ones smaller than the internal ones, deciduous, depressed ovate, widely depressed ovate or ovate, concave, apex acute, obtuse or rounded, base truncate, externally puberulent, internally puberulent; corolla 4–5-merous, petal white, 0.8–1.6 × 1.0– 1.4 mm, very widely ovate, concave, apex rounded, base truncate, externally puberulent to glabrous, internally puberulent to glabrous; staminal ring 0.2 mm, glabrous (rarely with scattered trichomes), stamens ca. 32, filament 1.8–3.2 mm long, glabrous, anther 0.24–0.32 × 0.24–0.32 mm, square, oblong or transversely oblong; ovary 0.6–0.8 × 0.8 mm, 2-locular, each locule with two ovules, style 3.8 mm long, glabrous, stigma punctiform, papillose. Fruit green when immature, reddish to vinaceous at maturity, 4–5 × 4–6 mm, depressed globose or globose, glabrescent to glabrous, pellucid dots covering the whole surface, remnants of calyx lobes present or not; seeds 1–2 (rarely 5).

Distribution and Habitat:—This species is known only from the municipality of Mucugê:in the “Parque Municipal de Mucugê” (a Protected Area) and the Serra de São Pedro. It occurs on rock outcrops close to watercourses.

Phenology:—The species was collected with flowers in December and February and with fruits in January and February.

Etymology:—The specific epithet refers to the vegetative branching pattern in which numerous long, slender lateral branches are almost all held nearly upright.

Conservation status:— Myrcia ascendens is just found in two localities close to the city of Mucugê, in Campo Rupestre vegetation (“Rocky Fields”). This type of vegetation is commonly subjected to anthropogenic fire ( Drummond et al. 2005). On account of this, and due to the restricted distribution of the species, we consider it as Critically Endangered (CR, criteria B2a, biii; IUCN 2001).

Discussion:— Myrcia ascendens shares with Myrcia densa monopodial branching, keeled immature branches and inflorescences branching only once or twice at the base. The former species differs in its vegetative branching (slender lateral branches inclined almost vertically), cataphyll scars rarely present (indicating almost continuous growth), shorter internodes and a shorter distance between the lateral veins and from the marginal vein to the margin. Other characteristics of M. ascendens show some overlap with M. densa but are still useful in its identification. These include narrow elliptic or oblanceolate leaf blades and the umbelliform inflorescence. Five seeds were found in a dissected fruit indicating that, at least occasionally, the species can have five ovules in the ovary.

Paratypes:— BRAZIL. Bahia: Mun. Mucugê, Parque Municipal de Mucugê , 13 o 0’S, 41 o 20’W, 30 January 2003 (fr.), T.C. Faustino 48 ( BHCB!) ; idem, 925 m, 12 o 59’59’’S, 41 o 20’52’’W, 12 February 2012 (fl., fr.), M.F. Santos 829 ( SPF!) ; idem, 925 m, 12 o 59’59’’S, 41 o 20’52’’W, 12 February 2012 (fr.), M.F. Santos 830 ( SPF!) .

Figures

FIGURE 1. Myrcia ascendens. A. habit. B. detail of keeled twig. C. blade with revolute margin. D. umbelliform inflorescence. E. floral bud and bracteoles. F. longitudinal section of flower at anthesis. G. fruit with calyx lobes remnants. Vouchers: A–F: Lewis CFCR 7074 (SPF); G. Santos 829 (SPF).

FIGURE 2. Species distributions. Myrcia ascendens=star; Myrcia attenuata=triangle; Myrcia costeira=circle; Myrcia rupestris=square; Myrcia subterminalis=diamond.