Begonia piraquara E.L.Jacques, 2023

Jacques, Eliane De Lima, 2023, Begonia piraquara (Begoniaceae) a new species from Atlantic Coastal Forest in the State of Rio de Janeiro, Brazil, Phytotaxa 612 (1), pp. 99-103 : 100-102

Begonia piraquara E.L.Jacques , sp. nov. ( Figs. 1 , 2 )

Begonia piraquara is most similar to B. fimbritepala E.L.Jacques (2020: 102) but differs in having cystoliths (vs. cystoliths absent), leaves with crenate margins (vs. ciliate), entire to slightly crenulate staminate tepals margins (vs. tepals with ciliate margins), tepals of staminate and pistillate flowers pinkish (vs. white), fruit wings with rounded apex (vs. truncate at apex).

Type:— BRAZIL. Rio de Janeiro: Realengo, Parque Estadual da Pedra Branca , 22º54’S, 43º27’W, 26 September 2022, E. L . Jacques , R. Z . Zanatta , & M. F. B . Nascimento 2084 (holotype RBR [ RBR 00057486 ] (2 sheets), isotype RB) .

Herbs, prostrate, rupicolous, 15–20 cm tall. Cystoliths present, best seen in hyaline structures. Stems prostrate, internodes 0.5–1.5 cm long, ferruginous, villlous. Stipules persistent, subcarnose and greenish when fresh, scarious and brown when dry, 2.5–3.3 × 1.4–1.5 cm, ovate, apex piliferous, with 2–4 trichomes, margins entire, villous on the principal veins, hairs ferruginous, 5–8 mm long. Leaves simple, petioles greenish, 4–8 cm long, villous, hairs ferruginous, with simple trichomes, leaf blades basifixed, entire, transversely elliptic, asymmetrical, carnosus 12.5–17 × 6–7.5 cm, base cordate, lobes not overlapping the petiole, adaxial surface glabrous, except by being villous nearest the petiole, green to slightly light green on the veins, abaxial surface villous on the principal veins to glabrescent, filiform hairs, ferruginous, 4–5 mm long, green to light reddish to green on the veins, venation actinododromous, 6 veins, margins crenate, apex acuminate. Inflorescences 6–7-branched cymes, ca. 20 cm long (including the rachis), rachis ca. 16 cm long (up to same size when fruiting), villous, hairs ferruginous, greenish to pinkish. Bracts caducous, 9–10 × ca. 4 mm, elliptic, apex piliferous, margins slightly crenulate near the apex, glabrous. Staminate flower: pedicels pinkish, 19–25 mm long, glabrous, tepals 4, external pair pinkish on outer surface, white on inner surface, broadly ovate, 8–11 × 9–12 mm, with microscopic glandular trichome on outer surface, apex rounded, margins entire, membranaceous, internal pair white on outer surface, except by being pinkish on central part, white on inner surface, elliptic, 8–10 × ca. 4 mm, glabrous, apex obtuse, margins entire, membranaceous, stamens 8–12, free, ca. 3 mm long, anthers yellow, oblong, ca. 2 mm long, rimose, extrorse, filaments ca. 1 mm long, connective not projecting, obtuse. Pistillate flower: pedicels pinkish, 11–15 mm long, with glandular trichomes, bracteoles absent, tepals 5, pinkish, unequal, widely ovate to obovate, 4 largest, 8–10 × 5–8 mm, 1 smallest, ca. 8 × 4.8 mm, with microscopic glandular trichomes on dorsal surface, apex acute, margins entire, except by being crenulate near the apex, membranaceous, ovary 3-locular, pinkish, 9–10 × 11–12 mm (including wings), with microscopic glandular trichomes, placentae entire, wings 3, subequal, the biggest wing 5–6 mm wide, smallest wings ca. 4 mm, stigmas 3, bifurcate, branches spiraled, yellow, 2–3 mm long, locular region light green, elliptic, 6–7 × 2.5–3 mm, glabrous. Capsule light brown when mature, depressed obovate, 12–15 × 14–18 mm (including wings), basally dehiscent, with glandular microscopic trichomes, peduncles 9–12 mm long, with glandular microscopic trichomes, brown, wings 3, subequal, the largest one rounded at apex, 5–6 mm wide, smallest wings with rounded at apex, 3–4 mm wide, locular region elliptic, ca. 7 × 3 mm, brown, with glandular microscopic trichomes. Seeds oblong.

Etymology:—The name honors the place where the species occurs, Piraquara.

Phenology: —Flowering and fruiting November to March.

Distribution and ecology: —This species is known only from the typical locality, Parque Estadual da Pedra Branca (PEPB), in the municipality of Rio de Janeiro, metropolitan region of the state of Rio de Janeiro. PEPB has three administrative centers: Camorim, Pau da Fome and Piraquara. The Cachoeira do Barata (Barata Waterfall) in the Piraquara center is one of the biggest attractions for visitors and the only location for Begonia piraquara , thus the type locality is under intense human interference. This species has small populations with about three mature individuals per square meter, in an area of occupancy smaller than 500 m ². It grows in the valley in submontane forests, on stoney walls covered by a thick layer of leaf litter, close to the Cachoeira do Barata, in a shady and very humid place, at an altitude approximately of 190 meters.

Provisional conservation assessment:— Begonia piraquara is provisionally assessed as VU D2 under IUCN Red List criteria ( IUCN Standards and Petitions Committee, 2022), with a plausible future threat that could lead the taxon to CR or EX in a very short time, due to being known in only one locality, close to intensely urbanized places, very small population and is subject to various threats such as wildfires, invasive species and a decline in the quality of habitat.

Additional specimens examined (paratype): — BRAZIL. Rio de Janeiro [Guanabara], Serra do Barata , March 1961, A. P . Duarte 5524 ( RB [ RB00054599 ]); Represa do Piraraquara, Realengo , 28 March 1972, D. Sucre 8751 ( RB [ RB00054563 ]); Realengo , Parque Estadual da Pedra Branca , 22º54’S, 43º27’W, 26 September 2022, E. L . Jacques , R. Z . Zanatta , M. F. B . Nascimento 2083 ( RBR [ RBR 00057485 ], RB) .

Taxonomic notes:— During the preparation of the manuscript for Begonia fimbritepala E.L.Jacques , herbarium materials from two specimens collected in the 1960s (Duarte 5524) and 1970s (Sucre 8751) were analyzed. The two collections were very similar to the habit and leaf shape of B. fimbritepala . Examination of the tepals of the staminate flower buds and notes of the colour of the flowers showed some differences, and the collections were from locations more than 50 km away from the typical locality of B. fimbritepala . My undergraduate student, Manoel Félix von Borell do Nascimento, recently recognized a species of Begonia with pink flowers, growing in a preserved area of the Atlantic Rainforest, open to public visitation, in the surroundings of the urban metropolis of Rio de Janeiro city, Brazil. Only 50 years after the first field expedition in this area, it was possible to elucidate the taxonomy and establish a new species for the state of Rio de Janeiro.

Figures

FIGURE 1. A–L. Begonia piraquara E.L.Jacques. A–B, Habitat; C, Habit; D, Details of leaf blades showing stipules E–F, Details of margins of leaf blades; G, Habit, showing inflorescence; H, Details of inflorescence; I, Staminate flower, outer and inner view and stamens J, Habit, showing inflorescence with pistillate flowers; K, Pistillate flowers, front view; L, Fruits. (A= 20 cm; B= 10 cm; C= 10 cm; D= 2 cm; E= 2 cm; F= 2 cm, G= 8 cm, H= 2 cm, I= 5 mm (square), J= 5 cm, K= 6 mm, L= 20 mm). A–L from Jacques 2084. Photos E.L. Jacques.

FIGURE 2. Distribution map of Begonia piraquara (circle). Blue line indicates the limits of area of the Pedra Branca State Park.