Begonia macrantha B.Das, J.Saikia & D.Banik, 2024

Das, Bikas, Saikia, Jadumoni, Konwar, Parthapratim, Siga, Appu & Banik, Dipanwita, 2024, A new berry-fruited Begonia (Begoniaceae) from Arunachal Pradesh, India, Phytotaxa 665 (1), pp. 45-54 : 47-52

Begonia macrantha B.Das, J.Saikia & D.Banik , sp. nov. § Platycentrum ( Figs. 1 , 2 & 3 ).

Type: — INDIA. Arunachal Pradesh: Lohit district, Tezu towards Hayuliang, 27°55’00.99” N, 96°19’06.07” E, elev. 633 m, 25 May 2022, Bikas Das, Jadumoni Saikia & Dipanwita Banik CSIR-NEIST 0217, fls. (Holotype: ASSAM, Isotype: CSIRNEIST).

Diagnosis:—The new species shows close resemblances with Begonia silletensis in having rhizomatous habit, terminal and branched inflorescence with fragrant flowers and berry fruited capsule. It differs from the latter in having completely glabrous lamina (vs. sparsely puberulous); stamens 600–650 (vs. 70–100); 8–10 tepals in pistillate flowers with numerous indistinct styles (vs. 4–6 tepals with 3–4 styles); 4–6 locular ovary (vs. 3 or 4 locular ovary) and drooping berries (vs. upright). The species also shows similarities with B. aborensis in general morphology having dioecious reproductive features, anthers with slightly extended connective, and a wingless globose ovary. However, it can be differentiated from B. aborensis having glabrous lamina and sparsely puberulent petiole towards base (vs. lamina pilose and densely villose petiole), peduncle glabrous to sparsely puberulent (vs. red pubescence), staminate flowers bearing 600–650 stamens (vs. 70–100); 8–10 tepals in pistillate flowers with numerous indistinct styles (vs. 4–6 tepals and 3–4 styles) and 4–6 locular ovary and drooping berries (vs. 3–5 locular ovary and upright berries). The characters of B. silletensis and B. aborensis were taken from revision of the genus by Camfield & Hughes (2018). Comparative morphology among these three species have been summarised in Table 2.

Dioecious, acaulescent, perennial, rhizomatous herb, 40–120 cm tall. Rhizome suffructescent, stout, 2.5–4 cm in diam., reddish-brown. Stipules deciduous, lanceolate, 1.2–2.4 × 0.8–1 cm, glabrous, red when young, turns blackish-brown towards maturity. Leaves 2–5 per plant; petiole terete, green tinged with red, pale red towards base, base sulcate, 35–120 cm long, puberulent; lamina ovate to broadly ovate, asymmetric, 45–80 × 30–45 cm, midrib 30–60 cm long, glabrous; adaxially green, abaxially whitish-green, base cordate, lobes slightly overlapping, apex acuminate, margin entire to dentate at vein ending, venation palmate, 6–8 veined, veins prominent below. Inflorescence terminal, branching twice; peduncles glabrous to puberulent; staminate primary branch 3–9 cm long, secondary 0.5–1.5 cm long, 1–4 flowers; pistillate primary branch 12–16 cm long and secondary branch 2–7 cm long, 2 or 3 flowers; Staminate flower pedicel 2–2.5 cm long, puberulous, tepals 4, outer tepals ovate-orbicular, 1.7–2 × 2.2–2.5 cm, pinkish-white, glabrous on both sides, apex rounded, margin entire, inner tepals oblong-elliptic, 2.5–2.8 × 1.6–2 cm, white to pale pink, glabrous, apex rounded; androecium dome shaped, 600–650 stamens, asymmetric, filaments 2–3 mm long, unequal, fused at base, anther oblong, ca. 2 mm long, dehiscing through longitudinal slits, hooded, connective extended. Pistillate flower pedicel 2–10 cm long, puberulent; fragrant; tepals 8–10, elliptic-oblong, glabrous, outer tepals pinkish-white, 3.8–4.2 × 2.5–3 cm, margin entire, inner tepals 4–5.5 × 2–2.5 cm, white, apex rounded; style indistinctly numerous, deciduous, stigma spirally twisted; ovary globose, maroon, puberulent, 4–6 locular, placentae bifid, wingless. Fruit globose, 2 or 3 fruits per infructescence, maroon to red, white verrucose, drooping, 2.5–3.0 × 2.2–2.5 cm, glabrous, lacking ridges or wings.

Etymology:— The specific epithet is derived from the large showy pistillate flowers of the species.

Phenology:— Flowering and fruiting from March-September

Habitat & ecology:— It grows along roadside banks, flourishing in an environment that is damp and shaded at an elevation range from 600–1,400 m ( Figure 2 ). The species grows in abundance and in clusters near constant water sources. The new species shares habitat with Begonia acetosella Craib var. hirtifolia Irmsch , Centella asiatica (L.) Urb., Elatostema sp. , Eupatorium sp. , Hydrocotyle sp. , Impatiens sp. , Polygonum sp. , Stephania sp. , and some ferns.

Conservation status:— The newly discovered species, B. macrantha , has been identified in multiple locations, primarily in the Lohit and Anjaw districts. The authors found a number of populations along the road connecting these districts, each consisting of approximately 50–100 individuals. Furthermore, collections made by Rekha Morris in the western parts of Arunachal indicated that the species has a widespread distribution. Given the need for more comprehensive surveys to determine the species’ exact population size, distribution range, and potential threats, it has been decided not to assign any threat category to B. macrantha at this time. Instead, following the guidelines of the IUCN Standards and Petitions Committee (2022), the species has been tentatively placed in the Data Deficient category (DD).

Additional Specimen examined:— INDIA. Arunachal Pradesh. Anjaw: Hayuliang to Chaglagam road, 1,355 m, 28°15’56.13” N, 96°34’21.60” E, 24 March 2022, B. Das, J. Saikia, D. Banik CSIR-NEIST 0251, frts. (CSIRNEIST) ; Delei valley , 1210 m, 96°36’ E, 28° 20’N, 25 July 1928, F.K.Ward 8486, ml. infl. (K) . Lohit: Near Demwe , 27°55’02.99” N, 96°19’20.67” E, 889 m, 25 May 2022, B. Das, J. Saikia, D. Banik CSIR-NEIST 0237, fls. (CSIRNEIST) ; Demwe to Udayak , 27°55’02.84” N, 96°19’24.31”, 895 m, 19 July 2023, B. Das, J. Saikia, P. Konwar CSIR-NEIST 0239, frts. (CSIRNEIST) . West Kameng: moist hill side, elev. 795’, north of Bhalukpung , 21 December 2005, Rekha Morris AR-143 ( CLEMS!, CLEMS0081769 , CLEMS0081770 ) ; moist hill side north of Bhalukpung , 11 April 2005, Rekha Morris AR-35 ( CLEMS! CLEMS0077888 ) ; Moist hillside, elev. 1,000’, north of Sessa , 11 April 2005, Rekha Morris AR-25 ( CLEMS! CLEMS0077887 ) ; moist cliffs north of Sessa , 11 April 2005, Rekha Morris AR-25 ( CLEMS! CLEMS0077886 ) ; on moist hill side north of Bhalukpung , elev. 800’, 11 April 2005, Rekha Morris AR-141 ( CLEMS!, CLEMS0081773 ) . Lower Subansiri: on wet muddy slopes, approx. 5194’, 24 Dec 2005, Rekha Morris AR-163a, 163b ( CLEMS!, CLEMS0077893 ) ; moist cliffs in underground seepage in hills north of Kimin , 14 April 2005, Rekha Morris AR- 47, fls. & frts., ( CLEMS!, CLEMS0081775 ) . Papum Pare: In deep gorge towards Gohpur , elev. 1,500’, 20 Dec 2005, Rekha Morris AR-141, lvs., ( CLEMS!, CLEMS0081772 , CLEMS0081771 ) ; in deep gorge towards Gohpur , elev. 1,500’, 17 Dec 2005, Rekha Morris AR-114, lvs., ( CLEMS!, CLEMS0077891 ) ; stream bank in gorge towards Gohpur , approx. 1,500’, 17 Dec 2005, Rekha Morris AR-113 ( CLEMS!, CLEMS0077890 ) .

Notes: — Camfield and Hughes (2018) noted in their observations on the species B. silletensis that Morris (2012) had mistakenly applied the name B. silletensis to a large Begonia species. Although these large begonias resembled B. silletensis , they showed distinguishing differences from the protologue of B. silletensis and were characterized by large solitary female flowers with 10 fringed tepals, a 5-locular ovary, and 5 or 6 styles. However, the type population of our new taxon did not exhibit the characteristic fringed nature of the tepals. This trait can vary, as the authors have observed both fringed and unfringed tepals in different populations of B. aborensis . Upon examination of the types of B. silletensis (lecto: K000634631!; isolecto: BM000017324!, K000634630!), it became apparent that it is a much smaller species. Here we consider B. macrantha to correspond to the large Begonia incorrectly identified as B. silletensis by Morris (2012, 2017).

However, confusion persists regarding the reproductive features of B. silletensis , as it has been reported as monoecious by Camfield and Hughes (2018) and Wahlsteen and Borah (2022), and dioecious by Tebbitt and Kaiyun (2002). Over the years, it has been observed that the berry-fruited species within the section Platycentrum exhibited significant variation in characteristics within species ( Aung et al., 2023). Begonia silletensis has a history of being confused with B. aborensis as both the species grow in the same geographic region and are similar in appearance. The authors have followed the species concept in the revision by Camfield and Hughes (2018), although their work was based on a very limited number of herbarium specimens available at that time. However, recent extensive sampling of this widely distributed yet poorly understood species from various geographical locations has revealed considerable variability among populations of B. silletensis . For instance, Hughes et al. (2018) reported some populations of B. silletensis from Yunnan had been found to possess convoluted styles as in currently described species, B. macrantha . To better understand the variability within this species and within this group, we recommend a wider sampling across different regions including both morphological and molecular data to define the species’ limits more clearly and to ensure their accurate identification.

Phylogenetic position: —The final dataset comprises 404 bases, accounting for gaps, with 277 conserved, 77 variable, and 57 parsimony informative characters. The Bayesian Inference phylogenetic analysis utilizing the ITS2 + 5.8S rRNA region revealed distinctly resolved clades corresponding to all sampled taxa. The three accessions of Begonia macrantha showed excellent BI-PP value of 0.99 in a well-supported sub-clade and distinctly placed alongside morphologically similar species comprising Begonia aborensis , Begonia silletensis and Begonia handelii . Thus, the current result showed distinguishing placement of Begonia macrantha among the berry-fruited begonias under the sect. Platycentrum .

Figures

FIGURE 1. Begonia macrantha B.Das, J.Saikia & D.Banik. A. Habit; B. Pistillate inflorescence; B’. Fruit; C. Staminate inflorescence.

FIGURE 2. Map showing collection localities of Begonia macrantha B.Das, J.Saikia & D.Banik from Arunachal Pradesh.

FIGURE 3. Begonia macrantha B.Das, J.Saikia & D.Banik. A. Leaf lamina; B. Male flower; C. Androecium; D. Stamen; E. Female inflorescence; F. Ovary cross-sections; G. Stigmatic surface; H. Ovary side view; I (Tepals of inner whorl) & I’ (Tepals of outer whorl).