Myrcia occulta Faria & E.Lucas, 2017

Faria, Jair E. Q., Lucas, Eve J. & Sobral, Marcos, 2017, Two New Species of Myrcia (Myrtaceae) from Brazil, Phytotaxa 319 (2), pp. 159-166 : 159-163

1. Myrcia occulta Faria & E.Lucas , sp. nov. ( Figures 1 , 2 ).

Type: — BRAZIL. Bahia: Formosa do Rio Preto , borda do Jalapão, margem da estrada entre Mateiros e Coaceral, ca. 58 km de Mateiros, 10º33’55” S, 45º56’12” W, 774 m, 13 November 2011 (fr.), J. E. Q. Faria, H. J. C. Moreira & J. B. A. Bringel 2172 (holotype UB!; isotypes HUEFS!, HUEG!) .

Myrcia occulta is apparently related to the stout and pubescent form of the widespread and morphologically variable Myrcia splendens (Sw.) De Candolle (1828: 244) , originally published as Myrtus splendens Swartz (1788: 79) , previously recognized as Myrcia deflexa (Poir.) De Candolle (1828: 244) , originally published as Eugenia deflexa Poiret (1813: 124) . Although Myrcia splendens is morphologically very plastic, Myrcia occulta differs from it consistently (in particular from morphologically similar individuals once recognized as Myrcia deflexa ) in its large, subglobose fruits to 22 × 14.5 mm (vs. cylindrical or subglobose, not exceeding c. 14 × 10 mm) and subcordate, sessile leaves with acute tips lacking an acumen (vs. elliptic-acuminate leaves with petioles to 9 mm and an acumen up to 1.5 mm). The two species are found in Cerrado vegetation with Myrcia occulta endemic to the biome while Myrcia splendens is widespread throughout the Neotropics; individuals previously recognized as Myrcia deflexa are found in the Amazon forest.

Subshrub to shrub 0.3–1.5 m; trichomes simple, amber-coloured. Stem with detaching cortex; twigs creamcoloured, densely tomentose, internodes 6.1–7.5 cm. Blades cordiform, 7.4–9.2 × 4.1–5.5 cm, 1.5–1.8 times longer than wide, coriaceous, adaxially sparsely tomentose, abaxially densely so; apex acute; base cordiform; midvein pilose on both sides, adaxially impressed to plane, abaxially raised; lateral veins 14–17 at each side, leaving the midvein at angles of 63 o –90 o; single marginal vein formed by the loops of the lateral veins and 1.5–2.5 mm distant from the margin in the middle of the leaf; gland dots not visible; petioles adaxially canaliculate, densely tomentose, 3–5 × 3 mm. Inflorescence paniculiform, axillary to terminal, densely tomentose, with 5 to 9 flowers, peduncle 2.4–4.2 mm; rachis 1–2.8 mm. Flower buds obovate, 8–10 mm × 6–8 mm; bracts ovate, 7–13 mm, sparsely tomentose along the base and apex of the adaxial side, abaxially densely tomentose, deciduous before or at anthesis; pedicels 0–9 mm, densely pubescent; bracteoles deciduous at anthesis, ovate, apex acute to acuminate, 4–7 mm, not connate, adaxially sparsely tomentose, abaxially densely so; ovary densely lanuginose externally; calyx lobes five, 5–6 × 4–5 mm, acute, persisting after anthesis, sparsely tomentose adaxially and densely so abaxially; petals five, orbicular to ovate, acute or rounded at the apex, 4–6 mm, sparsely tomentose apically and with visible gland dots adaxially, densely sericeous abaxially; staminal disc to 1 mm in diameter, sparsely tomentose, slightly depressed, the area between the disc and the style base densely tomentose; stamens about 300, filaments glabrous; style to 4 mm in bud, glabrous, stigma punctiform; ovary with two locules and two ovules per locule. Fruits sub-globose, light orange when immature, 19.8–22 × 12.2–14.5 mm, lanuginose with no visible glands; single seeded, testa membranous; embryo with two foliaceous cotyledons encircled by a well-developed hypocotyl.

Distribution:— Myrcia occulta is known from only two collections from the Jalapão microregion, a biologically unique lowland region of the Cerrado biome located on the boundaries between the states of Tocantins, Piauí, Maranhão and Bahia. The holotype was collected at the boundary between the states of Bahia and Tocantins and the paratype was collected by George Gardner in the poorly known “Chapada das Mangabeiras” locality ( Figure 3 ). “Chapada das Mangabeiras” is a term used to define a region that extends from the southern portions of the states of Maranhão and Piauí to southeastern Tocantins, in the neighbouring region where the holotype was collected.

Habitat:— Myrcia occulta grows in “ cerrado aberto ”, an open savanna that is very common in the range of the species.

Phenology:— Myrcia occulta was collected with flowers in September and fruits in November.

Conservation status:—This species is known from only two collections, only one of which has a precise locality— the municipality of Formosa do Rio Preto, from where 3,907 collections are recorded (CRIA 2016). This municipality has an area of c. 15,900 km 2 (IBGE 2016), resulting in an average of 0.2 collection/km 2, suggesting low collecting intensity rather than real threat is influencing the conservation category of Myrcia occulta . However, the region where the species was collected has been extensively cleared for agricultural use and this may have future consequences for the species. Considering all information presently available, we propose this species is DD (Data Deficient) according to IUCN conservation criteria (IUCN 2001).

Affinities:—This species is related to Myrcia splendens , from which it is distinguished in the diagnosis. Due to the presence of asymmetrical, paniculiform inflorescences, the hypanthium not prolonged beyond the insertion of the style and thick staminal ring, this species is likely to belong to informal “clade 5” in the phylogenetic scheme proposed by Lucas et al. (2011).

Etymology:—The epithet alludes to the collection of this species (overlooked until now) by George Gardner nearly two centuries ago and alludes to the rarity of the species that thrives in this still scarcely explored region. Paratype:— BRAZIL. Chapada das Mangabeiras, September 1839, G. Gardner 3178 (BM!, K [K000344968]!).

Figures

FIGURE 1. Myrcia occulta. A—fruiting branch, B—inflorescence detail with buds. (A—from the holotype, B—from the paratype at K).

FIGURE 2. Myrcia occulta. A—habit and habitat, B, C, D—fruiting branch. (A–D from the holotype; Photographer Henrique José Moreira da Costa).

FIGURE 3. Distribution map of Myrcia occulta and Myrcia matogrossensis in Brazil.