Eugenia neoriedeliana M.C.Souza & Giaretta

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 : 159-161

6. Eugenia neoriedeliana M.C.Souza & Giaretta (in Giaretta et al. 2018: 285).

≡ Mitranthes riedeliana O. Berg (1859: 595) . Chytraculia riedeliana (O.Berg) Kuntze (1891: 238) . Calyptrogenia riedeliana (O.Berg) Burret (1941: 546) . Neomitranthes riedeliana (O.Berg) Mattos (1990: 6) , not Eugenia riedeliana O. Berg (1857: 261) . Type:— BRAZIL. Rio de Janeiro: Habitat in silvis prope Madiocca, s.d., Riedel & Langsdorff s.n. (lectotype designated by Giaretta et al. (2018): K! [000331528]; isolectotypes: F [72823 negative number-photo!], LE! [6 sheets], M [0146828-photo!], NY [00405349-photo!], P! [00723175, 00723176, 00723177], S [herbarium number S-R-9472-photo!], OXF! [00071623, 00071645]). ( Figures 1E , 15 ).

Shrubs or trees 3 to 12 m tall. Young leaves with whitish trichomes up to 0.1 mm long, appressed, sparse abaxially, glabrous adaxially, glabrescent. Leaves with petioles 7–10 × 1–1.5 mm; blades 6.5–14 × 2.5–4.5 cm, obovate, elliptic or narrow-elliptic; base acute; apex abruptly acuminate, 1–2 cm long, or less often narrowly-acute; midvein canaliculate adaxially; secondary veins 7–10 per side; marginal veins two, the innermost 3–6 mm from the margin, the outermost 1–1.5 mm from the margin. Inflorescence terminal or axillar, fasciculiform; bracts 0.5–1 × 0.5–1.2 mm, wide-ovate; rachis 1–5 mm long, puberulent, terete, brownish; 1–4 pairs of flowers, pedicels 5–18 × 0.5–1 mm; up to three rachises sharing an axil; bracteoles 1–2 × 1 mm, ovate or wide-ovate, puberulent, persistent after anthesis. Flower buds 4–6 × 3.5–4.5 mm, obovate or elliptic, apiculate, calyx lobes partially fused and nearly closed leaving four vestigial free lobes at the tip, tearing transversely at the calyx base resulting in a calyptra-like structure, 4–5 mm diameter, puberulent, dense on hypanthium, brownish outside; petals 2–3 × 1.5–3 mm, wide-ovate or oblong, occasionally two petals fused at the base; stamens straight in the bud, filaments up to 6 mm long, anthers 0.4–0.6 mm long; staminal whorls flat, 5–6 mm diameter, rounded, not tearing at anthesis; style 5–6.5 mm long; ovary 2–locules, 9–15 ovules per locule. Fruit not seen.

Etymology:— The neo preceding the specific epithet means “new” from Greek in reference to the replacement name assigned to the species.

Distribution and habitat:— Eugenia neoriedeliana occurs in Southeastern Brazil (Rio de Janeiro), known from the Serra do Mar at elevations between 20 to 600 m ( Figure 16 ). It is usually a shrub but can also be a tall tree, both forms are mainly distributed on forest slopes or less often, on lowland coastal forest, within Ombrophilous Dense Forest in the Atlantic forest.

Phenology:— Flowers of Eugenia neoriedeliana have been collected from September to November ( Figure 6 ), the fruiting period is unknown.

Conservation status:— Eugenia neoriedeliana is endemic to Rio de Janeiro, known from two protected areas (APA Floresta do Jacarandá and REBIO do Tinguá) and non-protected areas in well preserved and disturbed sites with a restricted EOO of 1,570.7 km ². Although populations are under well preserved and protected areas, fragmented populations in the understory persist in other locations (Pão de Açúcar and Urca) experiencing historical and present anthropogenic pressure, leading to reduction in habitat quantity and quality. Likelihood of regional extinction is increased by invasion of exotic species, fire and human occupancy. Extinction risk re-evaluation is necessary and urgent to update threat status. Thus, it is suggested that this species should be rated as Endangered [EN B1ab(i, iii, iv)].

Comments:— Uncertainty surrounding the circumscription of Eugenia neoriedeliana was likely motivated by the bud dehiscence misleading Berg (1859) who assigned it to Mitranthes riedeliana , later combined with Neomitranthes riedeliana . The current circumscription within Eugenia is supported by straight stamens in the bud (vs. strongly curved in Myrcia s.l. and Pliniinae ) and confirmed its placement in Eugenia sect. Schizocalomyrtus by a molecular phylogeny ( Giaretta et al. 2019b). Eugenia neoriedeliana is often confused with E. tenuipedunculata and E. vattimoana but is easily distinguished by the bud tearing transversely at the calyx base resulting in a calyptra-like structure (vs. flower tearing in regular and irregular lobes, respectively).

Specimens Examined:— BRAZIL. Rio de Janeiro: Magé, 18 October 1984, fl., H . C . de Lima 2244 ( GUA!, INPA!, K!, RB!), 2 October 1984, fl., G . Martinelli 9905 ( CEPEC!, R!, RB!), 24 October 1984, fl., H . C . de Lima 2302 ( GUA!, K!); Nova Iguaçú , 16 September 2006, fl., L . M . Versieux 292 ( SPF!); Rio de Janeiro, 3 February 2015, fl., A . Giaretta 1489 ( K!, SPF!), 30 November 1976, fl., P . Occhioni 7981 ( RFA!) .

Figures

FIGURE 1. Diversity of Eugenia sect. Schizocalomyrtus. A–B. Eugenia acutata. A. Auxotelic inflorescence undergoing a second phase of vegetative growth. B. Flowers at anthesis. C–D. Eugenia tenuipedunculata. C. Flowers. D. Immature fruits. E. Eugenia neoriedeliana. Flower opening via transversal tearing at the calyx base resulting in a calyptra-like structure. F. Eugenia guanabarina. Flowers opening via transversal tearing at the calyx base resulting in a calyptra-like structure (S) placed in opposition to a petal (P). G–H. Eugenia longohypanthiata. G. Flower bud tearing irregularly at anthesis. H. Immature fruits crowned by the remnant of the calyx lobes (S) and the hypanthium (H). (A–B: A. Giaretta 1460; C: J.E.Q. Faria 1000; D: A. Giaretta 1493; E: A. Giaretta 1489; F: A. Giaretta 1035; G: A. Giaretta 1500; H: A. Giaretta 1502). Photos by A. Giaretta, except C by J.E.Q. Faria.

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 15. Eugenia neoriedeliana. A. Leaf branchlet with flower buds. B. Inflorescence and flowers buds. (A–B: H.C. de Lima 2244).

FIGURE 16. Distribution of Eugenia neoriedeliana.