Eugenia xinguana Sobral, M. A. D. Souza & G. Amorim 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 xinguana

description: 6. Eugenia xinguana Sobral, M.A.D.Souza & G.Amorim, sp. nov.
Type:— BRAZIL. Pará: Vitória do Xingu, 3°16’19” S, 51°45’50” W, 15 September 2014, E. Menezes Júnior PSACF_EX03557 (holotype RB!; isotype RBR). Figure 8.
Diagnosis:—This species is morphologically related to Eugenia stictopetala De Candolle (1828: 270; image M 0171122), from which it differs by its blades with midvein finely raised adaxially (versus impressed in E. stictopetala), with apex markedly acuminate up to 26 mm (vs. apex acute or, if acuminate, the acumen to 8 mm), pedicels to 10–14 mm (vs. to 5–6 mm), narrowly triangular bracteoles to 2 × 0.8 mm, these never basally fused (vs. ovate to rounded, to 2 × 2 mm, sometimes basally fused), flower buds 9–10 mm, the globe of the petals not entirely visible above the calyx and partly covered by the sepals (vs. flower buds to 6 mm, the globe of the petals clearly visible and not concealed by the sepals), sepals in two unequal pairs, the outer one 3 × 3.5–4 mm, the inner one 3–4 × 4–5 mm (vs. sepals about the same size, 1–1.5 × 1.7–2 mm), petals 10–15 × 7–10 mm (vs. 3–6 × 3 mm), stamens 10–12 mm (vs. 3–6) with anthers 0.6–0.8 × 0.5–0.6 mm (vs. to 0.8 × 0.2 mm) and styles 12–14 mm (vs. 5–8 mm). Additionally, the blades of this species may resemble those of Eugenia acrensis McVaugh (1956: 202; image NY 00404857), but differs by the adaxially raised midvein (vs. impressed in E. acrensis) and consistently glabrous twigs, blades and flowers (vs. twigs velutinous, blades with scattered dibrachiate trichomes abaxially and flowers velutinous).
Description:—Shrub to tree (height not recorded). Plants glabrous except for occasional cilia in flowers. Twigs terete, grey or brown when dry, slightly longitudinally striate, the cortex occasionally detaching in longitudinal stripes, the internodes 30–65 × 2–3 mm, occasionally with a pair of cataphylls 3–5 × 0.2–0.5 mm at their bases. Leaves with petioles 5–12 × 1–1.5 mm, semiterete; blades oblong or oblanceolate, 85–210 × 32–68 mm, 2.6–4 times longer than wide, discolorous when dry, light dull green adaxially and dull yellowish green abaxially; glandular dots 10 to 15/mm², of different sizes, the larger ones about 0.1 mm in diameter, visible on both faces and usually darker than the surfaces; base cuneate; apex acuminate to cuspidate in 6–26 mm; midvein narrowly raised adaxially, strongly raised abaxially; lateral veins 15 to 22 at each side, leaving the midvein at angles 70–80°, visibly raised on both sides, more so abaxially; marginal veins usually two, the inner one 2–5 mm, the outer one 0.5–1.5 mm from the revolute margin. Inflorescences axillary, with two flowers, the axis to 2 × 1 mm; bracts narrowly triangular, to 2 × 0.8 mm; pedicels 3–14 × 1 mm, applanate; bracteoles narrowly triangular as the bracts, to 2 × 0.8 mm, persisting at anthesis, with scattered cilia to 0.1 mm; flower buds globose or obovate, 9–10 × 8–10 mm, the hypanthium 1–1.5 mm; sepals triangular or widely so, in two unequal pairs, the outer one 3 × 3.5–4 mm, the inner one 3–4 × 4–5 mm; petals elliptic, 10–15 × 7–10 mm, with cilia to 0.2 mm; stamens 10–12 mm, the anthers elliptic or globose, 0.6–0.8 × 0.5–0.6 mm, sometimes with one apical gland; staminal ring to 4 mm in diameter and 1 mm thick; style 12–14 mm, the stigma punctiform; calyx tube absent; ovary with two internally glabrous locules and ca. 20 ovules per locule, these sometimes visibly separated in two distinct longitudinal rows. Fruits immature, ellipsoid, to 10 × 8 mm; seeds not examined.
Distribution, habitat and phenology:—This species is presently known from rainforests of the Brazilian states of Maranhão and Pará; although the state of Maranhão is not included in the political division of northern Brazil —it is included in northeastern Brazil —the collection site of the species, the municipality of Pindaré-Mirim, is located in the so-called Amazonian Biome from Maranhão (Rocha et al. 2020), an physionomically distinct from northeastern Brazil. Flowers were collected in July, September and October, and immature fruits in October.
Affinities:—This species is related to the widespread South American Eugenia stictopetala; for a detailed description of this species see McVaugh (1958: 739) under E. tapacumensis O. Berg (1855 –1856: 222), a synonym according to Govaerts et al. (2022); some of the numerical data of E. stictopetala cited in the protologue are based in McVaugh’s description. Regarding its sectional placement, the axillary inflorescences with up to two flowers suggest its placement in Eugenia section Umbellatae, according to the sectional classification proposed by Mazine et al. (2016, 2018).
Conservation:—The municipality of Pindaré-Mirim in Maranhão has an area of 268 km ² from which there are recorded only 44 collections, resulting in an average of 0.16 collection/km², and Vitória do Xingu, in Pará, has an area of 3,080 km ² from which about 2,600 specimens are recorded, with an average of about 0.8 collection/km². These collection sites are about 800 km apart. When verifying the Extent of Occurrence (EOO) of this species in Geocat (Geocat 2020), it results in an area of about 5,560 km ²; additionally, the species is presently known from less than 10 localities. These features fulfill respectively criteria B and B1 from IUCN conservation criteria for the status of Vulnerable (VU; IUCN 2012: 21); nevertheless we do not have additional information regarding decline or fluctuation in natural populations in order to properly assign this status to the species. Considering this, we score E. xinguana as DD (Data Deficient; IUCN 2019: 11).
Etymology:—The epithet is derived from the collection site of the type specimen.
Paratypes:— BRAZIL. Maranhão: Pindaré Mirim, Reserva Indígena do Pindaré, 3°38’ S, 45°28’ W, 15 October 1987, C.B.A. Bohrer 101 (HRB, MG!, RB!). Pará: Vitória do Xingu, Travessão 55, UTM 9655836 N, 417798 E, 27 July 2012, L.C. Antônio PSACF 630 (MG, RB!); idem, 3°18’49” S, 51°48’32” W, 15 October 2014, R.S.B. de Anorses PSACF_EX0896 (RB!); idem, 3°12’38” S, 51°46’55” W, 23 October 2014, A.C. Gonçalves PSACF_EX04116 (RB!); idem, 3°10’52” S, 51°47’18” W, 24 October 2014, D.A. Silva PSACF_EX04121 (RB!, RBR).
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 209-210, DOI: 10.11646/phytotaxa.536.3.1, http://zenodo.org/record/6331824