Myrcia pirapama D. F. Lima & Sobral 2021, sp. nov.
Creators: name: Sobral, Marcos
name: Lima, Duane F.
Publisher: name: Zenodo
Year: 2021
Subjects: Biodiversity
Taxonomy
Plantae
Tracheophyta
Magnoliopsida
Myrtales
Myrtaceae
Myrcia
Myrcia pirapama

description: 3. Myrcia pirapama D.F.Lima & Sobral, sp. nov.
Type:— BRAZIL. Minas Gerais: Santana de Pirapama, Serra do Cipó, Capela de São José, Trilha da Senhorinha, caminho a Congonhas do Norte, 18°54’36” S, 43°44’40.7” W, 1222 m elev., 24 November 2009, D.C. Zappi, W. Milliken, E. Nic Lughadha, J. Rando, N. Biggs & L. Moraes 2520 (holotype RB!; isotypes K, SPF). Figure 3.
Diagnosis:—This species is morphologically related to Myrcia hebepetala De Candolle (1828: 246, image M 0135567), but differs by the petioles 3.5–9 × 2.– 2.8 mm mm, 1.7–3 times longer than wide (versus petioles 4–5 × 1 mm, 4–5 times longer than wide in M. hebepetala), blades 45–102 × 33–52 mm, 1.1–2 times longer than wide (vs. 60–150 × 25–46 mm, 2.5–3.3 times longer than wide), intramarginal vein 1–2 mm from the margin, with 6–8% of the blade width external to this vein in the widest portion (vs. intramarginal vein 2–3 mm from the margin, with 13–16% of the blade width external to this vein in the widest portion), inflorescences with up to 15 flowers (vs. inflorescences with 30 flowers or more) and sepals 2.5–3 mm, triangular (vs. 1–2 mm, rounded to truncate).
Description:—Shrubs 1– 2 m. Twigs subterete, densely covered with simple brown or rufescent trichomes to 0.5 mm, these falling with age and then the twigs turning grey and slightly longitudinally striate when dry, the apical bud elliptic, to 12 × 8 mm, densely covered with brown trichomes, the internodes 15–70 × 3–5 mm. Leaves with petioles 3.5–9 × 2.– 2.8 mm, semiterete, slightly sulcate adaxially, with trichomes as the twigs, becoming glabrous and blackish with age; blades rounded to elliptic, 45–102 × 33–52 mm, 1.1–2 times longer than wide, discolorous, dull dark brown adaxially and lighter abaxially when dry, adaxially glabrous except occasionally for the midvein, abaxially densely covered with simple brown trichomes to 0.5 mm, these becoming scarce with age; apex widely acute to obtuse, rarely abruptly acuminate to 1 mm; base cuneate; glandular dots 4 to 8/mm², smaller than 0.1 mm in diameter, visible on both faces, especially abaxially, in adult leaves; midvein impressed adaxially (occasionally apparently raised due to the presence of trichomes) and markedly raised abaxially; lateral veins 9 to 13 at each side, raised on both faces, more so abaxially, leaving the midvein at angles about 45°; secondary lateral veins and higher order venation visible on both faces but with a smaller gauge than the main lateral ones; intramarginal vein continuous, 1–2 mm from the slightly revolute margin, the margin itself with a yellowish girdle to 0.2 mm wide. Inflorescences at the axiles of the distal pair of leaves, with trichomes as the twigs, with 6 to 15 flowers, the axis 40–90 × 2–4 mm, the peduncle 20–40 mm, racemiform or paniculiform, in this case with one or two secondary branches, these 5–10 mm, with up to three flowers apically clustered; bracts ovate, 4–9 × 3–5 mm, pilose as the inflorescences, falling at anthesis; flowers sessile; bracteoles elliptic, to 4 × 3 mm, adaxially glabrous, deciduous at anthesis; flower buds obovate or globose, to 8 × 8 mm, densely covered by simple rufescent trichomes to 0.6 mm, these usually uniform but sometimes more dense on the ovaries; sepals five, distinct from bud, ovate to triangular, 2.5–3 × 2.5–3 mm; petals obovate, 6–8 × 4–6 mm, glabrous adaxially and with whitish simple trichomes to 0.3 mm abaxially; stamens with filaments to 8 mm and anthers elliptic, to 0.7 × 0.3 mm, with one apical gland, the thecae slightly displaced between them; staminal ring 2.5–3 mm in diameter, 0.4–1 mm wide; calyx tube to 0.5 mm deep; style to 8 mm, with trichomes along its proximal half; stigma punctiform; ovary with two locules and two ovules per locule. Fruits not seen.
Distribution, habitat and phenology:— Myrcia pirapama is presently known only from a small area of rocky fields vegetation (“campo rupestre”) in the municipality of Santana de Pirapama, in the central portion of the southeastern Brazilian state of Minas Gerais. Flowers were collected in February and November.
Affinities:—This species is related to the southeastern and southern Brazilian Myrcia hebepetala, with which it is compared in the diagnosis. Regarding its sectional placement, due to its floral morphology of pilose sepals, pilose staminal ring and thecal morphology, it may be assigned to section Gomidesia, according to the sectional scheme proposed by Lucas et al. (2018).
Conservation:—The municipality of Santana de Pirapama has an area of 1,255 km ² (IBGE 2020) from where there are recorded 3,570 collections (INCT 2020), summing the sampling effort of 2.8 collections / km², a reasonable index if we consider the Brazilian average of 0.6 collection / km² (Sobral & Stehmann 2009). Considering this, the fact that only two specimens of Myrcia pirapama are known, it may be suggestive of its rarity; additionally, the specimens were collected in sites about 4 km apart, again suggesting that the species may occupy a relatively small area. Nevertheless, in the lack of additional information, for the moment we propose to score this species as DD (Data Deficient) according to IUCN conservation criteria (IUCN 2017).
Etymology:—The epithet is an apposition of the name of the collection site.
Paratype:— BRAZIL. Minas Gerais: Santana de Pirapama, Serra do Cipó (Serra da Lapa), Distrito de São José da Cachoeira, trilha de captação da Fazenda Toucan Cipó, campo rupestre com afloramentos e árvores esparsas, 19°00’22” S, 43°45’20” W, 680 m elev., 17 February 2007, V.C. Souza, D.C. Zappi, D.J.N. Hind, J. Paula-Souza, L. Jennings, G.O. Romão, J.G. Rando, M.A.P. Ferreira & E. Miranda 32585 (ESA, RB!, SPF).
description: Published as part of Sobral, Marcos & Lima, Duane F., 2021, Three new Brazilian Myrtaceae, pp. 277-284 in Phytotaxa 483 (3) on pages 282-283, DOI: 10.11646/phytotaxa.483.3.7, http://zenodo.org/record/5420988