Begonia inumbrata E.L.Jacques, 2022

Jacques, Eliane De Lima, 2022, Three Brazilian species of Begonia (Begoniaceae) from the state of Rio de Janeiro, Brazil, Phytotaxa 561 (2), pp. 138-150 : 142-144

Begonia inumbrata E.L.Jacques , sp. nov. ( Figs. 4 , 5 , 6 )

Begonia inumbrata is most similar to B. fluminensis Brade , but differs in having cystoliths (vs. absent); its densely villous petioles (vs. lanate); having an elliptic external pair of staminate tepals (vs. orbiculate); 7–8 stamens (vs. ca. 20); truncate connectives (vs. obtuse); and subequal tepals of pistillate flowers (vs. unequal).

Type:— BRAZIL. Rio de Janeiro: Paraty, Ilha do Algodão , 10 April 2022, 23º13.1’9.7” S, 44º36’54.3”W, 115m elevation, E. L. Jacques 2073, J. P. Costa , M. P. Azevedo et al. (holotype RBR 56198!, isotype RB!) .

Herbs prostrate, delicate, ca. 10 cm tall (including the inflorescence), villous. Cystoliths present, best seen in hyaline structures. Stem reptant, internodes inconspicuous, 0.3–0.5 cm long, brown, villous. Stipules persistent, 1.5–2 × 0.8 cm, triangular, apex setiferous, margins entire, with a crest of trichomes on the principal veins, subcarnose when fresh, scarious when dried. Leaves simple, petioles 8–13.5 cm long, vinaceous, densely villous, simple trichomes, hairs 2–2.5 mm long, leaf blades basifixed, 6–8(–9.5) × 4.5–6.5(–8.5) cm, entire, cordiform, asymmetrical, carnosous, base cordate, basal lobes rounded, overlapping the petiole, margins slightly undulate, ciliate, with simple trichomes, apex acute, adaxial surface with microscope glandular trichomes to glabrous, except villous near the petiole, shiny green, abaxial surface villous, densely along the principal veins, trichomes simple, hairs 3.5–5 mm long, vinaceous, veins 6–7, venation actinodromous. Inflorescence in 5-branched cymes, bearing ca. 15 flowers, 5–7 cm long (including the rachis), up to 11 cm long when fruiting, rachis ca. 4 cm long (up to 13 cm long when fruiting), villous, trichomes simple, reddish on basal portions to pinkish distally. Bracts persistent, 2–3 × ca. 1 mm, triangular, apex acuminate, margins entire, glabrous. Staminate flower: pedicels 6– 10 mm long, pinkish, puberulous, with microscopic glandular trichomes and simple trichomes, tepals 4, external pair 6–9 × 4–6 mm, elliptic, apex obtuse, margins entire, pinkishwhite, membranaceous, puberulous, simple trichomes, wide at the base and microscopic glandular trichomes, internal pair 6–8 × 2 mm, elliptic, apex obtuse, margins entire, white, membranaceous, glabrous, stamens 7–8, ca. 3 mm long, filaments ca. 0.5 mm long, free, connective projecting, truncate, anthers 2–2.7 mm long (including connective), oblong, extrorse, yellow. Pistillate flower: pedicels 8–9 mm long, pinkish, with microscopic glandular trichomes, bracteole 1, caducous, located on the apex of pedicel, linear, ca. 1 × 0.3 mm, pinkish-white, tepals 5, white, subequal, 6–8 × 2.7–4.1 mm, elliptic to broadly elliptic, apex acute to obtuse, margins entire, membranaceous, glabrous, ovary 3-locular, 5–6 × ca. 8 mm, pinkish-white, with microscopic glandular trichomes, wings 1–4 mm wide, unequal, flat, white to pinkish, placentae entire, stigmas 3, 1.5–2.5 mm long, bifurcate, branches spiraled, yellow. Capsule (7–)10–12 × 8–20 mm (including wings), basally dehiscent, glabrous, light brown when mature, depressed obovate, peduncles 10–11 mm long, glabrous, brown, wings 3, unequal, largest one 5–8 × 9–11 mm, apex acute, two smallest ca. 4 × 9 mm, straight to descendant, locular region ca. 8 × 4 mm, oblong, glabrous, seeds oblong.

Etymology:—Latin inumbratus, past participle of inumbrare, to shade, from umbra shadow, in reference to the habitat of the new species, which grows in shaded places.

Phenology: —Flowering and fruiting November to March and fruiting July.

Distribution and ecology: —This species is known only from the type locality, Ilha do Algodão, in the municipality of Paraty, Rio de Janeiro State, Brazil, in shaded parts of submontane forests, at an elevation of nearly 100 m. This island is in the region called the Costa Verde, and is one of the 63 islands that make up, along with the mainland region, the Cairuçu Environmental Protection Area (APA do Cairuçú). Begonia inumbrata has been observed growing in accumulations of leaf litter that collect on the stems of woody vines attached to a stone wall.

Provisional conservation assessment:— Due to being known only from a small island and being subject to various threats such as invasive species and a decline in the quality of its habit, this species is provisionally assessed as Critically Endangered (CR B2ab(i,ii,v)) under IUCN Red List criteria ( IUCN Standards and Petitions Committee, 2019).

Additional specimen examined (paratype): — BRAZIL. Rio de Janeiro: Paraty, Ilha do Algodão , 22 July 2020, M. C. Souza s.n. et J. P Costa. (56199 RBR!, RB!) .

Taxonomic notes:— Begonia inumbrata is a delicate, prostrate herb, around 10 cm tall with a villous indument. It can be easily recognized by its cordiform blades, with a cordate base and rounded basal lobes, overlapping the petiole, 7–8 × 5.5–6 cm, adaxial leaf surface with microscope glandular trichomes to glabrous, except villous near the petiole, shiny green, abaxial leaf surface villous, densely along the principal veins, simple trichomes, veins 6–7, inflorescence 5-branched cyme, pauciflorae, staminate flowers with elliptical external and internal tepals, pistillate flowers with subequal tepals, elliptic to broadly elliptic, and capsules depressed-obovate, glabrous. Begonia inumbrata is similar to B. fluminensis Brade (1945: 30) which shares the same leaf blades shape and fruit shape. In his original publication, Brade (1945) described Begonia fluminensis based on material collected in the north of the state of Rio de Janeiro, Frade de Machaé (currently Frade de Macaé, Macaé municipality). This location is distant from the type locality of B. inumbrata (south of the state of Rio de Janeiro), for more than 300 kilometers, in a straight line. Begonia fluminensis can be easily distinguished by being an herb, without cystoliths, with lanate indumentum, with simple and 2–8-branched trichomes, petiole lanate, with simple and 2-branched trichomes, hairs ca. 1 mm long, abaxial leaf surface lanose, with 6-branched trichomes, hairs clustered at the base, margins ciliate, with 8-branched trichomes, hairs clustered at the base, external pair of staminate tepals orbiculate, villous, with simple and 2-branched trichomes, hairs ca. 1 mm long, tepals of pistillate flower 8–12 × 2–10 mm, with microscopic glandular trichomes on the external surface, pedicels 10–15 mm long, villous, capsule scarcely villous, simple trichomes. Begonia inumbrata differs from B. fluminensis in having cystoliths, best seen in hyaline structures (vs. absent), petioles densely villous, with simple trichomes (vs. lanate, with simple and 2-branched), margins of leaf blades ciliate, with simple trichomes (vs. 8-branched trichomes, hairs clustered at the base), external pair of tepals in the staminate flower elliptic (vs. orbicular), puberulous, with simple trichomes, wide at the base and microscopic glandular trichomes (vs. villous, with simple, not wide at the base, and 2-branched trichomes), stamens 7–8 (vs. ca. 20), connective truncate (vs. obtuse), tepals of pistillate flowers subequal (vs. unequal), glabrous (vs. with microscopic glandular trichomes), ovary with microscopic glandular trichomes (vs. simple and microscopic glandular trichomes), capsule glabrous (vs. villous, simple trichomes).

Figures

FIGURE 4. A–O. Begonia inumbrata E.L.Jacques. A, Habit, showing infructescence; B, Details of indumentum in abaxial leaf surface; C, Trichome (abaxial leaf surface); D, Details of microscopic glandular trichomes and cystoliths (adaxial leaf surface); E, Staminate flower bud; F, Details of cystoliths and indumentum of the external staminate flower; G, Staminate flower; H, Androecium; I, Stamen; J, Pistillate flower, before anthesis; K, Details of rachis of inflorescence; L, Stipules; M, Pistillate flower, front side view; N, Stigmas; O, Capsule. Illustration by Maria Alice Rezende from M.C. Souza s.n. et al.

FIGURE 5. A–H. Begonia inumbrata E.L.Jacques. A, Habitat; B, Details of habitat; C, Habit; D, Adaxial leaf surface; E, Abaxial leaf surface; F, Staminate flowers; G, Pistillate flowers; H, Details of inflorescence, showing immature capsules (A–H from E.L. Jacques et al. 2073. (A= 350 m; B= 100 m; C= 6 cm; D= 1.5 cm; E= 1.5 cm; F= 7 mm. G, 7mm, H, 1.5 mm). A–H Photos E.L. Jacques.

FIGURE 6. Distribution map of Begonia inumbrata (rhombus). Dark line indicates the limits of area of the Cairuçu Environmental Protection Area.