Begonia corallina Carriére Rev. Hort.

Jacques, Eliane De Lima, Ribeiro, Maria Alice Martins & Tozin, Luiz Ricardo Dos Santos, 2023, Re-establishment of Begonia corallina Carrière (Begoniaceae) based on morphoanatomical evidence, Phytotaxa 609 (2), pp. 103-114 : 104-107

Begonia corallina Carriére Rev. Hort. , 47:89, 1875. ( Fig. 1 )

Type:— BRAZIL. Rio de Janeiro State. Rio de Janeiro Municipality: Parque Estadual da Pedra Branca , Prainha , 23°02’34”S, 43°30’48”W, 9 September 2021, E. L. Jacques & R. Z. Zanatta 2058 ( RBR [ RBR00058055 ]—three herbarium sheets— neotype, isoneotype RB designated here) .

Subshrub robust, erect, 1.5–2.5 m tall. Cystoliths absent. Stems erect, branched at apex, decumbent, internodes (1–)2– 3.5(–5.5) cm long, greenish, glabrous. Stipules caducous, 2–3 × 0.3–0.7 cm, elliptic, apex acute to acuminate, margins entire, glabrous, membranaceous. Leaves simple, petioles 2–3.5 cm long, greenish, glabrous, leaf blades basifixed, (11.5–)14–20 × 4–6.5(–7.5) cm, entire, transversely elliptic blades, asymmetrical, papyraceous, base cordate, margins slightly undulate, reddish, apex acute, adaxial surface with microscopic glandular trichomes, shiny green, with rounded silvery spots, abaxial surface with microscopic glandular trichomes, greenish, venation actinodromous, 5–8 primary veins. Inflorescences 4–5-branched cymes, bearing up to 27 flowers, 12–15 cm long (including the rachis), rachis 2.5–5 cm long (up to same size when fruiting), glabrous, reddish. Bracts early caducous, ca. 11 × 3 mm, ovate, apex acuminate, margins entire, cream colored, carnosus, glabrous. Staminate flower: pedicels (12–) 15–21 mm long, coral-red, glabrous, tepals 4, external pair 18–25 × 19–25 mm, widely ovate, apex acute, margins entire, coral-red, carnosus, glabrous, internal pair 9–11 × 2–4 mm, elliptic, apex acute, margins entire, coral-red, membranaceous, glabrous, stamens 38–49(–90), 3–6 mm long, filaments 1.5–2.5 mm long, free, connective not projecting, recurved, oblong, anthers 1–2 mm long (including connective), obovate, extrorse, yellow. Pistillate flower: pedicels 11–15(–25) mm long, coral-red, glabrous, bracteoles 2, caducous, located on the base of ovary, widely ovate, ca. 12 × ca. 12 mm, coral-red, tepals 5, coral-red, unequal, 2 largest ca. 17 × 13–15 mm, 3 smallest 12–16 × 7–10 mm, widely ovate to ovate, apex acute, margins entire, carnosus, glabrous, ovary 3-locular, 23–32 × 17–19 mm, locular region 14–15 × 8–9 mm, coral-red, glabrous, wings 4–5 mm wide, equal, plane, coral-red, placentae bilamellate, 1 lamellae with ovules only outer surface and another with ovules on both surfaces, stigmas 3, 6–7 mm long, bifurcate, base flabelliform, stigmatic papillae spiraled, yellow. Capsule 24–30(–37) × 15–23(–30) mm (including wings), basally dehiscent, glabrous, coral-red when immature, light brown when mature, cordiform, peduncles 10–15 mm long, glabrous, coral-red, wings 3, equal, plane, lunate, 4–6 mm wide, locular region 15–21 × 8–9 mm, elliptic, glabrous, seeds oblong.

Etymology:—The specific epithet refers to the coral red colour of the flowers.

Phenology:—Flowering from June to November and fruiting from June to December.

Distribution and ecology:—The species is restricted to the Parque Estadual da Pedra Branca, in the municipality of Rio de Janeiro, metropolitan region of the state of Rio de Janeiro, Brazil. Begonia corallina is known from populations with around one or two mature individuals, located in four areas. It grows in submontane and montane forests at an elevation of 100 to 620 m, on rock faces with accumulations of leaf litter or on the ground, in shady localities.

Provisional conservation assessment:— Begonia corallina has a direct threat to its survival, even if it occurs in a protected area. An important observation made in the field is that each subpopulation has a maximum of two mature individuals. Considering that each herbarium record represents a subpopulation, we can infer that there are less than 50 mature individuals. Based on this, it is possible to apply characteristic D and assess the species as Critically Endangered (CR) under IUCN Red List criteria (IUCN Standard and Petitions Committee 2022). Another important finding is the impairment of its perpetuation through sexual reproduction, which indicates that it is severely fragmented. The term “severely fragmented” refers to the situation where the increased risk of extinction of the taxon results from the fact that most of its individuals are found in small and relatively weak subpopulations ( IUCN 2022). These small subpopulations may become extirpated, with little chance of recolonization. Therefore, it is possible to apply condition “a” of criterion B, since the threats that Begonia corallina may suffer from illegal extraction, due to the ornamental potential and the impact of tourism, leading to a continuous decline. It is possible to meet the condition “b” of continuous decline inferred in terms of (i) extent of occurrence; (ii) area of occupancy; (iii) habitat quality; (iv) number of subpopulations and (v) mature individuals. Consequently, the species can be assessed as Critically Endangered (CR) according to criteria B1ab(i,ii,iii,iv,v); D.

Material examined:— BRAZIL Rio de Janeiro State. Rio de Janeiro Municipality: Mata rupícola da vertente sul da Serra da Piaba , 18 November 1971, D. Sucre 7918 ( RB [ RB00053267 ], RBR [ RBR00036916 ], US) ; Parque Estadual da Pedra Branca, Floresta do Camorim, Lage do Ravi (acesso pela rua Ant „o Fernandes), 28 August 1982, E. L. Costa et al. 206 ( RB [ RB00053325 ]); Maciço da Pedra Branca, Floresta do Camorim, Pico do Itaiací, [22°57’22”S 43°25’42”W], 6 September 2001, R. R. Oliveira et al 2439 ( RBR [ RBR00022544 ]); Parque Ecológico da Prainha, subida em direç„o ao Morro do Cruzeiro , [23°02’34”S, 43°30’48”W], 10 June 2004, R. D. Ribeiro 297 ( RB [ RB00303230 ]); Prainha, Parque Municipal da Prainha, Morro dos Cabritos , 23°02’34” S, 43°30’48”W], 4 December 2012, L. Kollmann et al. 12552 ( MBML [ MBML00008893 ], RB [ RB00787846 ]); ibidem, 4 December 2012, L. Kollmann et al. 12555 ( MBML [ MBML00007778 ], RB [ RB00788187 ]); Parque Estadual da Pedra Branca, Rio da Prata , 614 m, 22°56’18” S, 43°29’29”W, 28 September 2017, E. L. Jacques et al. 2000 ( RBR [ RBR00042483 ]); Parque Natural Municipal de Grumari / Parque Estadual da Pedra Branca, Prainha , Trilha entre a Pedra dos Cabritos e o Mirante Cruzeiro do Sul , [23°02’34” S, 43°30’48”W], 3 October 2019, L. O. L. Pedreira 84 ( RB [ RB01420395 ], RBR [ RBR00055775 ]); Parque Estadual da Pedra Branca, Cachoeira do Barata, Núcleo Piraraquara , Serra do Barata , 22°54’0.8”S, 43°27’00”W, 26 September 2022, E. L. Jacques et al 2081 ( RBR [ RBR00057483 ]) .

Taxonomic notes:—The protologue of Begonia corallina was published in a magazine dedicated to plants of ornamental interest ( Carrière 1875: 89). Brazil was cited as the probable origin of this species. No type was indicated. Carrière (1875) subsequently mentioned that B. corallina resembles B. argyrostigma Fisch. ex Link & Otto (1821: 23) ; currently B. argyrostigma is a synonym of Begonia maculata Raddi (1820: 406) . Irmscher (1925) treated B. corallina as a member of B. sect Gaerdtia (Klotzsch) A.DC., which is endemic to Brazil. This placement was followed by Barkley (1972) and Doorenbos et al. (1998). Smith & Wasshausen (1984) recognized B. corallina and its orthographical variant, B. carallina , as an accepted name. In 1974, Barkley & Golding related another orthographical variant name to B. corallina Carrière , B. carollina . Smith et al. (1986: 112, 153) considered B. corallina as a Brazilian species, known from cultivation, whose state of origin was unknown. Jacques & Mamede (2005) were wrong in attributing that Smith et al. (1986) recognized B. corallina and B. maculata as synonyms. In fact, they recognized B. corallina and B. maculata as a distinct species, but recognized morphological similarities between them including the leaf blades, which are finely white-spotted above ( Smith et al. 1986). However, Smith et al. (1986) represented B. corallina by an illustration of Begonia pulchella Raddi ( US 2775556!) and Golding & Wasshausen (2002) used the same illustration to represent B. corallina , creating more confusion in terms of taxon concepts. Begonia corallina is in GBIF (2023), POWO (2023) and WFO (2023) as a synonym of Begonia maculata . In Flora e Funga do Brasil (2023), B. corallina is a name of uncertain application. Most likely, B. corallina was first considered a synonym of B. maculata in the World Checklist of Selected Plant Families ( WCSP) (data supplied on 2012). Jacques & Mamede (2005) and Jacques & Gregório (2020) considered B. corallina as a name with uncertain application. Hughes et al. (2015 –) consider B. corallina as an accepted name. Up to then, the few specimens labelled as B. corallina deposited in herbaria were identified by the first author as B. maculata . Only after finding three populations vegetatively similar to B. maculata in the field, but with coral-red inflorescences, flowers and immature fruits, was it possible to reassess the taxonomic concept of B. corallina .

Considering that the protologue of Begonia corallina does not cite a type collection ( Carriére 1875: 89) and that we have been unable to locate any specimens that could be original material of B. corallina , it is highly likely that no original material exists. Further, there is no evidence that any material remains from the Carrière herbarium ( Williams 2004). Detailed examination of Carriére’s original description supported the reestablishment concept of B. corallina . We therefore designate the neotype of B. corallina as E. L. Jacques & R. Z. Zanatta 2058 ( RBR 00058055), which is mounted on three herbarium sheets: one of the plant specimens with pistillate flowers, another with staminate flowers buds an the third with fruits. The neotypification of this name was based on the protologue of B. corallina .

Begonia corallina resembles B. maculata , a widely dispersed species from Rio de Janeiro State, by the presence of transversely leaf blades, with rounded silvery spots above, and cordiform capsules. In herbarium materials lacking pistillate flowers and fruits, B. corallina can be confused with B. maculata , however, B. corallina is easily recognized by its larger staminate flowers and ovary with bilamellate placentae, 1 lamella with ovules on the outer surface only and another with ovules on both surfaces. Flowering living specimens of B. corallina are best distinguished from B. maculata by their fleshier tepals and coral red flowers.

Figures

FIGURE 1. A–H. Begonia corallina Carrière. A, Habitat; B–C, Habit; D, Apex of stem, showing rounded silvery spots on leaf surface; E, Base of stem, showing plant branch; F, Staminate flowers; G, Pistillate flowers; H, Fruits. A–B, D–H from Jacques et al. 2058; C, R. Zanatta. Bars: A–C = 20 mm, D, G-H = 5 mm, E = 10 Cm., F = 7 mm.