Begonia atlantica M. D. Miranda & E. L. Jacques. A, Abaxial 2022, sp. nov.
Creators: name: Miranda, Marcelo Dias
name: Jacques, Eliane De Lima
Publisher: name: Zenodo
Year: 2022
Subjects: Biodiversity
Taxonomy
Plantae
Tracheophyta
Magnoliopsida
Cucurbitales
Begoniaceae
Begonia
Begonia atlantica

description: Begonia atlantica M.D.Miranda & E.L.Jacques, sp. nov. (Figs. 1, 2, 3)
Diagnosis. Begonia atlantica is closely related to Begonia microinduta M.D. Miranda (2021: 49). It differs chiefly in having villous stems (vs. glabrous) and a ciliate leaf margin (vs. not ciliate).
Type: — BRAZIL. São Paulo State: Município Caraguatatuba, Jardim das Gaivotas, colina associada ao Pico do Jaraguá, erva vivendo sobre grandes rochas no interior da floresta, trecho próximo do cume da colina, ambiente não ciliar. 23°37’54”S, 45°27’43”W, elevation ca. 100 m, 22 August 2020, M. D. Miranda 12 (holotype: RBR!).
Herbs, rhizomatous, rupicolous, reptant or rarely decumbent, 4–21 cm tall. Stem cylindrical, internodes (0.5–) 1–1.5 (–2.5) cm long, ca. 4 mm diam, lenticellate, greenish-red or reddish, villous, with simple trichomes, hairs hyaline, 2–4 mm long. Stipules tardily deciduous, ca. 7 × 4 mm, triangular, apex piliferous, 3 mm long, margins entire, dorsal surface villous, trichomes simple, red. Leaves simple, petioles 6.3–7.5 cm long, 2.5–3 mm diam., cylindrical, red, villous, with simple trichomes throughout their entire length, hairs hyaline, ca. 3 mm long, leaf blades basifixed, 5–8.3 × 1.7–3.3 cm, transversely elliptic, asymmetrical, coriaceous, apex acuminate, base cordate, basal lobes not overlapping the petiole, margins serrulate to dentate, repand, ciliate, adaxial surface glabrous, flattened, dark green, light green on the veins, slightly iridescent when lit, shiny, abaxial surface glabrous, scarcely pilose on the principal vein, trichomes simple, vinaceous or greenish, venation actinodromous, primary veins 8. Inflorescence 3-branched cymes, ca. 2.5–4 cm long (up to 7–10 cm long when fruiting), peduncles 1.6–1.9 cm long, pilose. Bracts persistent, primary bracts 10–11× 7–9 mm, ovate, apex acute, Staminate flower pedicels whitish, ca. 16 mm long, scarcely pilose, trichomes simple, tepals 4, external pair white, 8–13 × 8–10 mm, ovate, apex slightly acute, margins entire, membranaceous, pubescent, except in the upper third, simple and 2-branched trichomes, hairs reddish, 3–4 mm long, internal pair white 8–10 × 3.5–4.5 mm, oblanceolate to elliptic, base acute, apex obtuse, margins entire, glabrous, stamens 15–19, ca. 2 mm long, filaments 0.5–1 mm long, free, anthers 1.5–1.8 mm long (including rounded connective), oblong, rimose, extrorse, yellow. Pistillate flower pedicels reddish, ca. 12 mm long, glabrous, bracteole absent, tepals 3, white, equal, 8–9 × 7 mm, broadly elliptic, apex acute, margins ciliate in the upper third, hairs red, dorsal surface sparsely pilose, ovary reddish-white, 3-locular, ca. 5 × 5.5 mm, trichomes glandular, placentae entire, stigmas 3, 1.7–2 mm long, bifurcate, branches spiraled, with stigmatic papillae distributed along the branches, yellow. Capsule 9–14 × 12–16 mm (including the wings), ellipsoid, dehiscent in basal portion, glabrous, reddish-green when fresh, light brown when mature, peduncles 1.5–2.5 cm long, trichomes glandular, wings 3, unequal, the largest 5–6 × 8–13 mm wide, the smallest 2–3 × 8–10 mm wide, locular region ca. 6 × 4 mm, elliptic, glabrous, seeds oblong.
Etymology: —The specific epithet is a geographic reference to the habitat of the species.
Phenology: —Flowering and fruiting from August to January.
Distribution and ecology: — Begonia atlantica is endemic to São Paulo state, and is so far known only from the type locality in the Caraguatatuba municipality. Its natural habitat is a hill positioned on the south face of the Pico do Jaraguá, where it grows exclusively over igneous rocky outcrops under tree canopy. It is found far from streams and the forest is quite dry with large, scattered rocks across the slope. The population is distributed across four different rocks separated from each other by less than 100 meters.A search around the area was conducted to try to locate further subpopulations but none were encountered.
Provisional IUCN assessment: — B. atlantica is provisionally classified as Critically Endangered (CR B2ab & C2a(i)) due its area of occupancy (AOO) being less than 10 km ² (B2), and because it is found in a single locality (B2a) which is currently undergoing decline in habitat quality caused by construction activity (B2b), and the number of mature individuals in each subpopulation being less than 50 (C2a(i)) (IUCN Standards and Petitions Committee, 2019). Threats such as habitat loss and fragmentation caused by surrounding construction of the Tamoios highway increases the need for monitoring and conservation action for the remaining individuals.
Additional specimen examined (paratype):— BRAZIL. São Paulo State: Município Caraguatatuba, Jardim das Gaivotas, colina associada ao Pico do Jaraguá, erva vivendo sobre grandes rochas no interior da floresta, trecho próximo do cume da colina, ambiente não ciliar. 23°37’54”S, 45°27’43”W, elevation ca. 100 m, 28 August 2020, M.D. Miranda 13 (RBR!).
Taxonomic notes: — Begonia atlantica is similar to B. itaipeensis E.L. Jacques (2019: 57), B. lorenzii E.L.Jacques (2020: 39), B. microinduta M.D. Miranda (2021: 49) and B. windischii L.B.Sm. ex S.F.Sm. & Wassh. (1999: 27) by having three tepals in the pistillate flowers; this is not a common characteristic in Brazilian Begonia species (Jacques, 2019). Begonia microinduta can be recognized by its narrow leaves with a cuspidate apex; pubescent petioles, and leaf veins on the abaxial surface and peduncles covered with short microscopic trichomes. Begonia atlantica differs from B. microinduta in having a smaller stature ca. 4–21 cm tall (vs. 19–60 cm); villous stems (vs. glabrous); stipules pilose on the midrib and close to the margins, with simple trichomes (vs. pilose only on the midrib, with microscopic trichomes); villous petioles, hairs ca. 3 mm long (vs. pubescent, with hairs less than 1 mm long), coriaceous leaves (vs. membranaceous); and a ciliate leaf margin (vs. not ciliate; Fig. 7). Begonia atlantica is also similar to B. windischii in having staminate flowers with a pilose indumentum externally, with simple and 2-branched trichomes. It can be distinguished by its smaller stature (4–21 cm vs. 19–60 cm tall); pilose stems (vs. glabrous); shorter internodes (0.5–2.5 cm vs. 1.2–4.5 cm); its densely pilose indumentum of the petioles (vs. scarcely pilose in upper portions, with a ring of trichomes at the stem close to the base of the petiole and at the apex); its leaves with cuspidate apices (vs. acute) and ciliate margins (vs. not ciliate), and flat veins on both leaf surfaces (vs. prominent on both leaf surfaces); and its staminate tepals, which are externally pubescent, except in the upper third, (vs. pilose in the center).
description: Published as part of Miranda, Marcelo Dias & Jacques, Eliane De Lima, 2022, Two new diminutive species of Begonia (Begoniaceae) from the north coast of São Paulo State, Brazil, pp. 147-158 in Phytotaxa 550 (2) on pages 147-148, DOI: 10.11646/phytotaxa.550.2.4, http://zenodo.org/record/6641111