Eugenia dichasiata Giaretta, 2021

Giaretta, Augusto, Lucas, Eve & Sano, Paulo Takeo, 2021, Taxonomic monograph of Eugenia sect. Schizocalomyrtus (Myrtaceae: Myrteae), a group within Eugenia with unusual flowers, Phytotaxa 524 (3), pp. 135-177 : 151

3. Eugenia dichasiata Giaretta , sp. nov.

Type:— BRAZIL. Rio de Janeiro: Magé, estrada da Parada Modelo para Cachoeiras de Macacu, ramal de acesso ao Centro de Primatologia da FEEMA, 22º 29’ 44.1’’ S, 42º 54’ 42.8’’ W, ca. 50 m a.s.l., 2 September 2006, fl., P. Fiaschi & A.Q. Lobão 3141 (holotype: SPF! [176157-herbarium number] ; isotypes: BHCB, K!, RB! [00484917]). ( Figure 9 ) .

Eugenia dichasiata is morphologically similar to Eugenia acutata but differs in having glabrous flowers (vs. puberulent or pubescent), with calyx lobes equal in size (vs. two unequal pairs), staminal whorls rounded and not tearing at anthesis (vs. squared and tearing slightly at anthesis), and inflorescences usually in 3–flowered dichasial arrangements (vs. rarely) with up to two rachises sharing an axil (vs. up to one rachis), glabrous (vs. pubescent).

Trees 3 to 16 m tall. Young leaves glabrous. Leaves with petioles 5–18 × 1.5–2 mm; blades 8–18 × 2–6 cm, oblanceolate or elliptic; base acute or cuneate; apex acuminate or abruptly acuminate, 1–2 cm long, or acute; midvein canaliculate adaxially; secondary veins 15–22 per side; marginal veins two, the innermost 1.5–3 mm from the margin, the outermost 0.5 mm from the margin. Inflorescence terminal or axillary, fasciculiform; bracts 1 × 1.5 mm, wideovate; rachis 1–20 mm long, terete, puberulent; 1–4 pairs of lateral flowers emerging from the rachis, pedicels 15–55 mm long, flattened, glabrous; flowers often expressing 3–flowered dichasial arrangement, middle flower sessile or with a pedicel up to 1 mm long, lateral flowers with pedicels 5–10 × 0.2–0.4 mm, glabrous; up to two rachises sharing an axil; bracteoles 2–3 × 0.5 mm (seen from young flower), lanceolate, glabrous, deciduous before anthesis. Flower buds 5–7 × 4–6.5 mm, obovate, calyx lobes partially fused but free at the tip leaving an aperture of 1–4 mm diameter with borders often abaxially revolute, tearing regularly at anthesis into 4 externally glabrous lobes, 2.5–4 × 2.5–3 mm,; petals 5–6 × 4.5–5 mm, wide-ovate; stamens straight in the bud, filaments up to 6 mm long, anthers 0.9–1.2 mm long; staminal whorls flat, 4–5 mm diameter, rounded, not tearing at anthesis; style 4–6 mm long; ovary 2–locules, 14–17 ovules per locule. Fruits 10–12 × 9–11 mm, ellipsoid, colour when ripe unknown, glabrous, crowned by the remnant of the regular calyx lobes; seed 1.

Etymology: —The specific epithet is in reference to the dichasial arrangement of the inflorescence.

Distribution and habitat: — Eugenia dichasiata is distributed in Southeastern (Espírito Santo, Rio de Janeiro and São Paulo) and Northeastern Brazil (Bahia), known from the coastal forest in the Serra do Mar, at elevations between 30 to 200 m ( Figure 10 ). Eugenia dichasiata is shrub or tree known from coastal vegetation on slopes and from lowland forests, within Ombrophilous Dense Forest in the Atlantic forest.

Phenology: —Flowers of Eugenia dichasiata have been collected from September to December and fruiting in December ( Figure 6 ). Fruiting period is unknown.

Conservation status:— Eugenia dichasiata is known from one protected area (REBIO União) and non-protected areas in well preserved and disturbed sites with EOO of 108,000 km ².Although this species is not threatened throughout its entire range, there is a significant risk of local extinction due to intense suppression of vegetation from urbanization in all States of its range that has left less than 20% natural vegetation ( SOS Mata Atlântica 2017). Fragmented landscape intensified by loss of habitat quality increases its risk of extinction, therefore regional assessment is encouraged to identify further threats. Thus, it is suggested that this species should be rated as Near Threatened (NT).

Comments:— Eugenia dichasiata has flowers with fused calyces that develop via the heterosepalous pattern and fasciculiform inflorescences often with the 3-flowered dichasial arrangement associated with Eugenia sect. Schizocalomyrtus .This placement is also supported by the molecular phylogeny ( Giaretta et al. 2019b).An inflorescence with a dichasial arrangement is assumed to be the standard condition, however, some specimens may not express this trait (see Almeida 68, Pirani 3390 and Hatschbach 68366), but other than this, these specimens lack morphological differences. When the inflorescence is fasciculiform, rather than dichasial, Eugenia dichasiata can be confused with E. acutata but differs by the inflorescence with up to two rachises sharing an axil (vs. up to one rachis per axil), leaves with darkish petioles when dry (vs. not darkish), and glabrous flowers (vs. pubescent or puberulent).

Paratypes:— BRAZIL. Bahia: Itabela , 17 September 1968, fl., J . Almeida 68 (CEPEC!, RB!). Espírito Santo: Conceição da Barra , 10 October 1998, fl., G . Hatschbach 68366 ( G!, MBM!, MBML!, SP!); Marilândia, 5 December 1994, fl., J . R . Pirani 3390 ( SP!, SPF!) . Rio de Janeiro: Caxias , 17 November 1999, fl., S . J . Silva-Neto 1331 ( K!, RB!, UB!); Magé, 2 September 2006, fl., P . Fiaschi 3141 ( K!, RB!, SPF!); Rio das Ostras, 18 November 1997, fl., P . P . Oliveira 82 A ( SP!) , 10 December 1997, fr., P . P . Oliveira 82 B ( SP!) . São Paulo: Ubatuba , 16 November 1993, fl., P . C . Lobo 29370 ( SP!) .

Figures

FIGURE 6. Frequency distribution (n) of flowering (black-line triangle) and fruiting (grey-filled triangle) stages based on herbarium material of Eugenia sect. Schizocalomyrtus.

FIGURE 9. Eugenia dichasiata. A. Leaf twig with young flower buds. B. Inflorescence and young flowers in dichasial arrangement. (A–B: P. Fiaschi 3141).

FIGURE 10. Distribution of Eugenia dichasiata.