Myrcia auriculata T.Fernandes, Sobral & J.M.A.Braga, 2019

Fernandes, Thiago, Sobral, Marcos, Santos, Matheus Fortes & Braga, João Marceloalvarenga, 2019, Myrcia auriculata (Myrtaceae), a new species from the Brazilian Atlantic Forest, Phytotaxa 399 (1), pp. 77-82 : 78-80

Myrcia auriculata T.Fernandes, Sobral & J.M.A.Braga , sp. nov. ( Figures 1 and 2 ).

Diagnosis:—This species is apparently related to M. truncata Sobral (in Sobral et al. 2012: 42), from which it differs by the auriculate leaf base (versus truncate in M. truncata ), inflorescences 15–55 × 0.9–1.8 mm (versus 100–115 × 90–110 mm) and flowers with four calyx lobes (versus five).

Type:— BRAZIL. Rio de Janeiro: Silva Jardim, Aldeia Velha, trilha para o povoado Toca da Onça, 22°25’28”S, 42°17’56”W, 800 m, 25 July 2018 (fr), T. Fernandes, R. Benvenuti, D. Göpfert & K. Ribeiro 290 (holotype RB!, isotypes HUFSJ!, NIT!).

Treelets up to 5 m tall. Vegetative branching often monopodial, occasionally sympodial, twigs terete, glabrate, when immature green and smooth, drying yellowish or greyish with conspicuous glands, when mature brownish, drying ferruginous and often varnished with inconspicuous glands, the internodes 31–55 × 2–3 mm, cataphylls ca. 4.2 × 2.5 mm, triangular, puberulent, deciduous, leaving scars at the base of all internodes. Leaves subsessile, the petioles 1–1.5 × 2–2.5 mm, slightly pulvinate at base and evident only abaxially, applanate adaxially, drying blackish; blades 13–26 × 2.7–5.9 cm, 4.4–4.8 times longer than wide, oblong-lanceolate, slightly discolorous to concolorous in nature, markedly discolorous, dull dark green adaxially and dull yellow green abaxially when dry; glandular dots 6–10/mm², approximately one gland per areole, smaller than 0.1 mm in diameter, perceptible on both faces but usually well visible when backlit; base auriculate with reflexed lobes; apex attenuate, 1.5–3 cm long; midvein sulcate adaxially and markedly raised abaxially with conspicuous glands when dry; lateral veins 30–40 per side, leaving the midvein at angles about 80°, raised on both sides, more so abaxially; secondary lateral veins visible and slightly raised, slightly thinner than the main lateral ones; marginal veins two, the inner one 1.5–3 mm, the outer one 0.5–0.8 mm from the plane margin. Inflorescences in reduced panicles (generating a racemiform pattern), axillary at the terminal node, with one branch per axil, the main axis 15–55 × 0.9–1.8 mm, glabrous, green, drying brown, the peduncle 10–20 mm long, the lateral branches when present one to two, these 8–10 mm long; number of flowers unknown; bracts and bracteoles unknown. Flowers (based on its remnants on fruits) with four deciduous calyx lobes, elliptic or hemispheric, free and well-spaced between them, in two slightly unequal pairs, the smaller one 1–1.5 × 1.8–2 mm, the larger one ca. 2 × 2 mm, with very appressed simple white trichomes to 0.1 mm long at the adaxial face; staminal ring up to 2.5 mm in diam. and to 0.7 mm thick, glabrous or with sparse and very appressed simple white trichomes to 0.1 mm long; hypantium tube to 1 mm long, not tearing at anthesis. Fruits 14–20 × 12–20 mm, globose or slightly ellipsoid with rounded base, purple to black when ripe, crowned by the persistent hypanthium tube and occasionally by the calyx lobes, these dry (marcescent) and not accrescent; seeds immature, one per fruit, the testa light brown, easily detachable, embryo pinkish with one visible hypocotyl and two foliaceous cotyledons.

Etymology: —The name Myrcia auriculata alludes to its leaves with auriculate bases.

Distribution, habitat and phenology: —The species is apparently endemic to the southeastern Brazilian state of Rio de Janeiro, where it was collected in rainforests about 800 m elev. in Aldeia Velha, a small district of the municipality of Silva Jardim ( Figure 2 ). Immature and mature fruits were collected in May and July, respectively.

Conservation status: — Myrcia auriculata is presently known from a forest remnant of Atlantic rainforest of Aldeia Velha, a discontinuous, strongly fragmented and non-protected area, where human activity represents the main threat. Although few collections are reported for the area ( CRIA 2019), Aldeia Velha is near (but outside the limits) the protected area Reserva Biológica de Poço das Antas, the most well-surveyed area of Silva Jardim, with 50 km ² ( ICMBIO 2019) and 1508 collections ( CRIA 2019), with the high average of 30 collections/km²; additionally, there are about 7500 collections from the municipality of Silva Jardim ( CRIA 2019, JABOT 2019), in an area of 930 km ² ( IBGE 2019), resulting in an average of 8 collections/km², also a significant sampling effort. Considering this, the lack of collections of M. auriculata may be an indicative of its rarity. Its Extent of Occurrence (EOO, IUCN 2017) of less than 100 km ² suggests a status of Critically Endangered (CR; criterion B2a, biii, IUCN 2017).

Paratype: — BRAZIL. Rio de Janeiro: Silva Jardim,Aldeia Velha, trilha para o povoado Toca da Onça, 22°25’28”S, 42°17’56”W, 800 m, 20 May 2018 (fr), T. Fernandes et al. 221 (NIT!, RB!).

Affinities: —The combination of the presence of cataphylls in all nodes, globose fruits crowned by the persistent hypanthium tube and free and deciduous calyx lobes matches the morphology of Myrcia sect. Sympodiomyrcia . Within this section, M. auriculata is aparently related to M. truncata , differing in the characters given in the diagnosis.

M. auriculata and M. truncata are also apparently related to other species of M. sect. Sympodiomyrcia with large leaves, such as M. insigniflora M.F.Santos (2014: 99) , M. plusiantha Kiaersk. (1893: 66) and M. tenuifolia (O. Berg 1857 –1859: 67) Sobral (2006: 136). According to the most recent phylogenetic hypothesis, these species do not form a monophyletic group ( Santos et al. 2016) and can be distinguished by the characters given in Table 1.

Figures

FIGURE 1. Myrcia auriculata. A. Fruiting branch (scale: 42 mm). B. Leaf blades in vivo, showing the reflexed lobes (scale: 19 mm). C. Leaf blades in sicco, showing the auriculate bases (scale: 18 mm). D. Cataphyll and cataphyll scar at the base of the internode (scale: 2.5 mm). E. Detail of the inflorescence and immature fruits (scale: 8 mm). F. Detail of an immature fruit (scale: 4 mm).

FIGURE 2. Distribution map of Myrcia auriculata (triangle). Grey lines represent the limits between municipalities.