Eugenia humaitana Sobral & M.A.D.Souza, 2022

Souza, Maria Anália Duarte De, Sobral, Marcos & Amorim, Gabriela, 2022, Six new species of Eugenia (Myrtaceae) from Amazonian Brazil, Phytotaxa 536 (3), pp. 197-212 : 200-202

2. Eugenia humaitana Sobral & M.A.D.Souza , sp. nov.

Type :— BRAZIL. Amazonas: Humaitá, rodovia do estanho, a 150 km de Humaitá, 8 o 7.5’ S, 61 o 49’ W, 25 September 1979, G. Vieira, J. Zarucchi, A.S.L. Silva, C.D.A. Mota & O.P. Monteiro 145 (INPA!, holotype; isotypes RB!, MO, NY, US). Figures 2 , 3 .

Diagnosis:—This species is morphologically related to Eugenia cribrata McVaugh (1969: 174 ; image F 0065132F), but differs by its elliptic blades 47–76 × 18–36 mm, 2–2.6 times longer than wide ( versus narrowly elliptic blades, 66–111 × 22–44 mm, 2.5–3 times longer than wide in E. cribrata ), with acute or slightly acuminate apex, the acumen 3–5% of the blade’s length ( vs. visibly acuminate, the acumen 10–17% of the blade’s length), glabrous bracts, pedicels and flowers ( vs. pilose), pedicels 2.5–5 × 0.5–0.6 mm ( vs. 15–20 × 0.5 mm) and sepals in two unequal pairs ( vs. about the same size); it may also resemble Eugenia egensis De Candolle (1828: 281 ; for additional description see McVaugh 1958: 695; type image M 0137682), but differs by its concolorous or slightly discolorous blades ( vs. visibly discolorous in E. egensis ), 2–2.6 times longer than wide ( vs. 2.5–3.5 times longer than wide), with apex acuminate to 3–5% of the blade’s length ( vs. acuminate to 10–25% of the blade’s length), with glandular dots 3 to 8/mm², these of unequal size, the larger ones to 0.2 mm in diameter ( vs. glandular dots 20 to 30/mm², these about the same size and smaller than 0.1 mm in diameter), intramarginal vein 2–4 mm from the margin ( vs. 0.5–1 mm), inflorescences fasciculiform, without a developed axis ( vs. racemiform, with an axis 3–20 mm long), pedicels 2–5 × 0.5–0.6 mm ( vs. 10–15 × 0.1–0.2 mm) and sepals in two unequal pairs ( vs. about the same size).

Description:—Shrub to 2 m. Plants glabrous except for scattered rufescent cilia 0.1–0.2 mm in the bracteoles and sepals. Twigs glabrous, applanate, drying light grey; internodes 17–35 × 1–2 mm. Leaves with petioles semiterete, adaxially applanate, black when dry, 4–6 × 1.7–2 mm; blades elliptic or slightly elliptic–obovate, 47–76 × 18–36 mm, 2–2.6 times longer than wide, concolorous or slightly discolorous, adaxially dull dark brown or blackish when dry, sometimes lighter abaxially; base cuneate; apex acute or acuminate in 2–4 mm; glandular dots 3–8/mm², in two or more distinct sizes, the larger ones to 0.2 mm in diameter, black when dry, visible and raised on both sides, more visibly so abaxially; midvein adaxially biconvex, occasionally becoming flat in older blades, abaxially strongly raised; lateral veins 8–9 at each side, leaving the midvein at angles 60–70°, finely raised adaxially and more visibly so abaxially, secondary lateral veins and higher order venation occasionally perceptible; intramarginal veins usually two, the inner one 2–4 mm, the outer one 0.9–1 mm, and occasionally a third vein perceptible 0.2–0.3 mm from the usually plane margin, this with a dark brown shining girdle to 0.2 mm wide. Inflorescences axillary or ramiflorous, fasciculiform, the central axis not developed, with 2–4 flowers; bracts widely ovate, to 1 × 1 mm; pedicels 2.5–5 × 0.5–0.6 mm, applanate; bracteoles ovate or elliptic, to 1 × 0.8–1.2 mm, persisting after anthesis, sometimes carenate; flower buds not seen; ovary to 1 mm, somewhat verrucose; sepals four, elliptic or widely triangular, in two slightly unequal pairs, the smaller ones 1.5–2 × 2 mm and the larger ones 2–2.5 × 2–2.6 mm, sometimes with a hyaline margin to 0.2 mm wide, patent after anthesis, glandular as the blades, the glands sometimes markedly excavate; petals, stamens and style not seen; staminal ring to 2.2 mm in diameter and 0.4 mm thick; calyx tube absent or to 0.1 mm deep; ovary with two internally glabrous locules, with 8 to 11 ovules per locule. Fruits not known.

Distribution, habitat and phenology:—This species is presently known only from the type specimen, collected in lowland sandy fields (“campinas”) of the municipality of Humaitá, in the southern portion of the state of Amazonas; flowers were colleted in November.

Affinities:—This species is morphologically close to Eugenia cribrata , a species known from Colombia and Venezuela ( Govaerts et al. 2022) due to its marked glandular dots, and may occasionally be confused with the widespread South American Eugenia egensis ; it is compared with both species in the diagnosis. Considering its fasciculiform inflorescences it may be assigned to Eugenia section Umbellatae , according to the sectional classification of Mazine et al. (2016, 2018).

Conservation status:—The municipality of Humaitá has an area of 33,111 km ² from which there are recorded 9,657 collections, resulting in the low collection index of 0.3 collection/km². Considering that the species is known only from the type, collected forty years ago, the species must be scored as Data Deficient (DD) according to IUCN conservation criteria ( IUCN 2019: 72).

Etymology:—The epithet is allusive to the collection site, the municipality of Humaitá.

Figures

FIGURE 2. Eugenia humaitana. Holotype (scale = 50 mm).

FIGURE 3. Eugenia humaitana. Detail of blade with marked glandular dots (left) when compared with E. egensis (right; specimen of E. egensis: A.R. Lourenço 379, INPA!). Scale = 5 mm.