Eugenia humaitana Sobral & M. A. D. Souza 2022, sp. nov.
Creators: name: Souza, Maria Anália Duarte De
name: Sobral, Marcos
name: Amorim, Gabriela
Publisher: name: Zenodo
Year: 2022
Subjects: Biodiversity
Taxonomy
Plantae
Tracheophyta
Magnoliopsida
Myrtales
Myrtaceae
Eugenia
Eugenia humaitana

description: 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.
description: Published as part of Souza, Maria Anália Duarte De, Sobral, Marcos & Amorim, Gabriela, 2022, Six new species of Eugenia (Myrtaceae) from Amazonian Brazil, pp. 197-212 in Phytotaxa 536 (3) on pages 200-202, DOI: 10.11646/phytotaxa.536.3.1, http://zenodo.org/record/6331824