Myrcia advena M.F.Santos, 2025

Santos, Matheus F., 2025, Taxonomic monograph of Myrcia sect. Eugeniopsis (Myrciinae, Myrteae, Myrtaceae), an endemic clade of Eastern South America, Phytotaxa 703 (1), pp. 1-100 : 12-14

1. Myrcia advena M.F.Santos , sp. nov. Type: — Brazil. Distrito Federal: Brasília, University campus, cerrado along road parallel to lago Paranoá , 6 October 1975 (fl., fr.), Oldenburger 1685 (holotype UB!; isotypes K!, NY!, SP!) ( Figures 3 , 4 ).

Diagnosis: — Myrcia advena is related to Myrcia oblongata but differs by the swollen node (vs. slender), cataphylls persistent or deciduous (vs. deciduous), leaf blade with base obtuse to rounded or truncate to emarginate (vs. narrowly cuneate to rounded), abaxial surface glabrous or subglabrate (vs. pubescent to puberulent), and inflorescence with opposite apical branching (vs. subopposite).

Description:— Shrub to tree, 2.5 to 5.0 m high. Trichome white, ochraceous or often reddish, simple or dibrachiate, 0.08–0.48 mm. Twig when young flattened, puberulent, when mature greyish (when dry), cylindrical, cortex slightly cracked; branching monopodial, internode 1.5–5.2 cm, node swollen; cataphylls present (sometimes more than one pair per SGU), deciduous (scale-like) or persistent (leafy); buds sericeous. Leaf concolorous, chartaceous, blade 1.9– 8.9 × 1.4–4.2 cm, widely elliptic, ovate to widely ovate, obovate to widely obovate, sometimes circular, apex obtuse to rounded, base obtuse to rounded, truncate or emarginate, margin plane, secondary veins 3–8 mm apart, held at an angle of 65–80° relative to the midvein, marginal vein 1.0– 1.5 mm from the margin, tertiary veins conspicuous to inconspicuous in both surfaces, areoles 0.5–1.0 mm, pellucid dots conspicuous in the abaxial surface, ca. 7 per mm 2; adaxial surface glabrous, secondary veins plane to raised; abaxial surface subglabrate to glabrous, secondary veins plane to raised; petiole 2–4 × 2–4 mm, canaliculate, puberulent to glabrous. Inflorescence 2.5–9.0 × 2.0–4.0 cm, 10– 21 flowers, axillar at the subterminal nodes of the SGU (central bud developing a vegetative branch), one inflorescence per axillary bud, inflorescence pherophyll persistent, opposite branching (rarely subopposite), three branching per node (rarely four), rachis puberulent to subglabrate, first internode of central rachis ca. 1 mm wide; bracts deciduous, not seen; bracteoles ca. 0.8 × 0.6 mm, deciduous, lanceolate to widely ovate, concave or keeled, apex acuminate or rounded, base truncate, externally subglabrate to glabrous, internally glabrous (often ciliate). Flower bud 3.5–4.0 × 3.0– 3.5 mm, obovate, corolla apparent before anthesis; hypanthium ca. 0.8 mm extending above the summit of the ovary, not tearing at anthesis, externally puberulent to glabrous, pellucid dots covering the whole surface; calyx 5–merous, lobes 0.4–1.2 × 0.6–2.0 mm, not fused, apparently persistent, depressed ovate to widely depressed ovate, concave, apex rounded, both surfaces puberulent to glabrous (often ciliate); corolla 5–merous, petals white, 0.8–2.4 × 1.4–2.8 mm, widely depressed ovate or very widely ovate, concave, apex rounded, both surfaces puberulent to glabrous (often ciliate); staminal ring 0.2–0.4 mm wide, subglabrate to glabrous, stamens 43–65, filament 2.0– 3.8 mm long, anther 0.24–0.56 × 0.32–0.48 mm, gland at the apex; ovary 0.8–1.2 × 0.8–1.2 mm, obconic, style ca. 4.8 mm long, glabrous, stigma punctiform. Fruit immature green, globose, base rounded, glabrous, totally covered by pellucid dots, hypanthium and calyx present; seeds not seen.

Distribution and Habitat: —The new species is the only member of Myrcia sect. Eugeniopsis endemic to the Cerrado domain, currently recorded exclusively in the Brazilian Federal District ( Figure 4 ). It inhabits the savanna vegetation (cerrado sensu stricto) and swamp areas (“brejo”) at elevation around 1,000 meters.

Phenology: —Flowering and fruiting specimens have been collected in August to November.

Etymology: —The specific epithet advena (meaning “foreigner”) honours the immigrant workers who, through their labour, built the Brazilian Federal District, the only known location of this new species. Additionally, Myrcia advena represents a “migrant” within Myrcia sect. Eugeniopsis , providing a westward expansion of the group distribution.

Conservation Status:— According to the Geocat analysis, the species has an Extent of Occurrence of 23 km 2 (threshold of Critically Endangered), and the Area of Occupancy is 12 km 2 (threshold of Endangered) (sensu IUCN 2022). The species is known from only four records in the Federal District, a well-documented region (sensu Campbell 1989) with more than one record per km 2 (estimation based on records of speciesLink; CRIA 2024). The Cerrado vegetation is frequently affected by anthropogenic fire, a situation intensified in recent years by climate changes ( Tomas et al. 2024). Due to these factors, we preliminarily classify this species as Critically Endangered (CR, criteria B2a, biii; IUCN 2022).

Taxonomy:— Myrcia advena is closely related to Myrcia oblongata , sharing several distinctive features: a shrub to tree habit, trichomes usually white to ochraceous, monopodial branching, leaf blade with an apex usually obtuse to rounded (though less angular in M. advena ), axillary inflorescence at subterminal nodes of the SGU, pherophyll persistent (sometimes deciduous in M. oblongata ), obovate flower bud with a visible corolla, and pentamerous flower with persistent calyx. These species exhibit a disjunct distribution, and further phylogenetic studies including M. advena would be valuable to explore their shared biogeographic history.

Illustrations and images in previous works:— None.

Additional specimens examined:— BRAZIL. Distrito Federal: Brasília , 12 August 1980 (fl.), R . C . Mendonça 144 ( K); ibidem, 22 September 1975 (fl.), J . E . Paula 1072 ( IBGE, SPF); ibidem, 25 September 1961 (fl.), E . P . Heringer 8695 ( SP) .

Figures

FIGURE 3. Isotype of Myrcia advena (Oldenburger 1685 [SP]).

FIGURE 4. Distribution of Myrcia advena (triangles) and Myrcia vellozoi (circles). Solid lines represent the boundaries of South American countries and Brazilian states. The grayscale reflects elevation.