Myrcia acutisepala 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 acutisepala

description: 2. Myrcia acutisepala D.F.Lima & Sobral, sp. nov.
Type:— BRAZIL. Minas Gerais: Grão Mogol, Parque Estadual de Grão Mogol, afloramentos rochosos acima da Várzea dos Quartéis, campos rupestres, 16°31’01” S, 42°56’44” W, 750 m elev., 20 October 2018, G. Martinelli, N. Pougy, E. Fernandez & C. Baez 20355 (holotype RB!, isotypes RBR, SPF). Figure 2.
Diagnosis:—This species is morphologically related to Myrcia eriocalyx De Candolle (1828: 247, image M 0137571), from which it differs by the trichomes on twigs and blades to 0.8 mm and sparse in adult parts (versus. 1–2 mm, visibly present even in adult parts in M. eriocalyx), blades with adaxial surface glabrous or glabrescent, somewhat shining (vs. adaxial surface of blades usually dull and at least puberulous), these usually 2.2–3.7 times longer than wide (vs. about 2 times longer than wide) and with 8 to 15 lateral veins (vs. 6 to 8 lateral veins), and sepals to 2.5 mm (vs. to 1 mm).
Description:—Shrubs 1– 2 m. Twigs subterete, densely covered with simple brown or rufescent, curly trichomes to 0.5 mm, these falling with age and then the twigs turning grey and slightly longitudinally striate when dry, the apical bud lanceolate, to 4 × 2 mm, densely covered with brown trichomes, the internodes 15–25 × 1.5–2 mm. Leaves with petioles 3–3.5 × 1–1.2 mm, semiterete, slightly sulcate adaxially, with trichomes as the twigs, becoming scarce with age, at least when young with visible tufts of up to 10 linear white colleters 1–2 × 0.1 mm; blades narrowly elliptic, lanceolate or oblong, 36–48 × 13–17 mm, 2.2–3.7 times longer than wide, discolorous, dark green or brown when dry, densely covered on both faces with simple rufescent or yellowish trichomes 0.4–0.8 mm when young, in adult blades the adaxial surface glabrous and occasionally lustrous, sometimes the trichomes persisting along the midvein; base obtuse or widely cuneate; apex acute; glandular dots 10 to 12/mm², smaller than 0.1 mm in diameter, usually visible abaxially; midvein slightly impressed adaxially and markedly raised, darker than the surface abaxially; lateral veins 8 to 15 at each side, plane or finely raised adaxially, visibly raised abaxially, leaving the midvein at angles about 60°; secondary lateral veins and higher order venation perceptible at least abaxially, with a smaller gauge than the main lateral ones; intramarginal vein continuous, 0.5–1 mm from the plane or slightly revolute margin. Inflorescences at the axiles of the distal pair of leaves, densely covered with trichomes to 0.4 mm, with 3 to 9 flowers, paniculiform, the axis 45–55 × 1 mm, the peduncle 25–35 mm, usually with one pair of secondary branches, these 4–7 mm and with up to three flowers apically clustered; bracts ovate, to 3 × 1.5 mm, pilose as the inflorescences, falling at anthesis; flowers sessile; bracteoles triangular, to 4 × 1 mm, with trichomes as the inflorescence, early deciduous; flower buds obovate, 6–7 × 5 mm; sepals five, distinct from bud, triangular, acute, 2.5 × 2–2.5 mm, occasionally tearing partially at the base at anthesis, adaxially scarcely and abaxially densely covered by simple rufescent trichomes to 0.2 mm; petals five, elliptic, to 4 × 3 mm, adaxially glabrous and abaxially densely covered with whitish simple ascending trichomes to 0.3 mm; stamens with filaments to 4 mm, the anthers elliptic, 0.5–0.6 × 0.2 mm, with one connectival gland, the thecae slightly displaced between them; staminal ring to 3 mm in diameter and 1 mm wide, densely covered with trichomes to 0.2 mm; calyx tube to 1 mm deep, with trichomes as the ring; style 8–9 mm, with simple hyaline trichomes to 0.5 mm scattered along its proximal half, the stigma punctiform and papillose; ovary with two locules and two ovules per locule. Fruits globose to slightly ellipsoid, dark green (according to collection Martinelli et al. 20355), 7–8 × 5–7 mm, with two or three seeds, these with dark brown, shining, easily detachable testa, the embryo with two distinct cotyledons and well developed hypocotyl.
Distribution, habitat and phenology:—This species occurs along the rocky fields formation (“campos rupestres”) in the central portion of the southeastern Brazilian state of Minas Gerais, in the municipalities of Buenópolis and Grão Mogol, at about 1,060 m elev.; flowers were collected in February, October and November, and fruits in October.
Affinities:— Myrcia acutisepala is related to the southeastern Brazilian Myrcia eriocalyx (for description see Amorim 2017: 112), with which it is compared in the diagnosis. Due to the floral morphology, with densely pilose staminal ring and stamens with displaced thecae, it can be assigned to section Gomidesia (O.Berg) B.S.Amorim & E.Lucas (in Lucas et al. 2018: 6; basionym: Gomidesia O. Berg, 1855 –1856: 5).
Conservation:—Although an evaluation of the Extent of Occurrence (EOO) of this species via Geocat (Bachman et al. 2011, Geocat 2020) resulted in an EOO of 373 km ²—consequently pointing to a status of Endangered (EN) according to IUCN conservation criteria (IUCN 2017)—it is prudent to recognize that this EOO is a result of the fact that three of the four specimens known for the species were collected only a few kilometers apart to each other, in the municipality of Grão Mogol, and the third was collected in Buenópolis, about 200 km apart. Considering this, we suggest this species to be presently scored as DD (Data Deficient) according to IUCN conservation criteria.
Etymology:—The epithet is allusive to the acute sepals of the flowers of the species.
Paratypes:— BRAZIL. Minas Gerais: Buenópolis, Cachoeira de Curimataí, 14 November 2010, E. Barbosa, J. Cordeiro & E.F. Costa 2926 (HUFSJ!, MBM!). Grão Mogol, Parque Estadual de Grão Mogol, localidade de Extrema, campos rupestres, 163513 S, 425726 W [probably “ 16°35’13” S, 42°57’26” W ”], 860 m elev., 25 February 2018, G. Martinelli, N. Pougy, T. Lima, M. Bocaiúva & H. Rocha 20084 (RB!); Parque Estadual de Grão Mogol, 22 November 2019, S.G. Resende GMS181 (BHCB, image!).
description: Published as part of Sobral, Marcos & Lima, Duane F., 2021, Three new Brazilian Myrtaceae, pp. 277-284 in Phytotaxa 483 (3) on pages 281-282, DOI: 10.11646/phytotaxa.483.3.7, http://zenodo.org/record/5420988