Begonia hooveriana Wiriadinata (2013: 445)

Thomas, Daniel C. & Ardi, Wisnu H., 2020, Synopsis of Begonia (Begoniaceae) of southwest Sulawesi and the Selayar Islands, Indonesia, including one new species, Phytotaxa 437 (2), pp. 73-96 : 83-86

7. Begonia hooveriana Wiriadinata (2013: 445) ( Fig. 1 & 4 )

Sect. Petermannia

Type:— INDONESIA. Sulawesi, South Sulawesi, Tanah Toraja, Central Park Makele , alt. 900 m, 9 Mar. 1998, W.S. Hoover 889 ( BO [1454234]!, lectotype designated here; isolectotype BO[5 sheets: BO1454232 !; BO1454233!; BO1454235!; BO1454236!; BO1454237 !]) .

Additional literature:— Tebbit (2005: 100) [drawing]; Thomas et al. (2011: 252) [as ‘ B. sp. I’; identification key].

Description:— Perennial, erect, monoecious herb to ca. 140 cm tall. Stem branched; internodes 2.5‒15 cm long, slightly swollen at the nodes, pale green or reddish, with white spots, glabrous except for microscopic glandular hairs. Leaves alternate; stipules semi-persistent, ca. 1.5‒4.7 × 1.2‒2.1 cm, ovate, with an abaxially prominent midrib, margin translucent, keeled, apex narrowed into bristle up to 3 mm long, glabrous, green; petioles 5–20 cm long, concolourous with the stem, glabrous; lamina basifixed, 8–28 × 5–17.5 cm, ovate to elliptic, asymmetric, base cordate and lobes not overlapping to overlapping, apex acuminate, margin broadly dentate, denticulate between the larger teeth, teeth bristle-pointed, adaxial surface green or reddish green, smooth and shiny, iridescent with pale green veins or sometimes variegated with white bands between the veins, glabrous; abaxial surface pale green, reddish-greenish or maroon in the central part of the leaves, glabrous or very sparsely hairy with bristly hairs on the veins; venation palmate-pinnate, primary veins (5–)7, actinodromous, secondary veins craspedodromous. Inflorescences: protogynous; female inflorescences 2-flowered, 1‒ 4 female inflorescences basal to male inflorescence part, peduncles (3‒) 15‒58 mm long, bracts caducous, up to 15 × 9 mm, broadly ovate, pale green, glabrous; male inflorescences paniculate-cymose, composed of up to 7 subumbellate partial inflorescences, each with up to 12 flowers, peduncle of male inflorescence 1−40 mm long, pale green, glabrous, bracts caducous, 10‒15 × 9‒15 mm, broadly ovate to suborbicular, pale green or reddish-green, glabrous. Male flowers: pedicels 8–40 mm long, pale green or reddish-green, glabrous; tepals 2, white, white tinged pink, or greenish-whitish, 12–23 × 15–28 mm, broadly ovate to suborbicular, base slightly cordate to truncate, apex rounded, outer surface glabrous; androecium of ca. 72‒88 stamens, yellow, filaments up to ca. 1.5 mm long, slightly fused at the very base, anthers up to ca. 1.2 mm long, obovate, dehiscing through unilaterally positioned slits that are ca. ½ as long as the anthers. Female flowers: pedicels (10−) 15−30 mm long, pale green, glabrous; tepals 5(−6), white, unequal, larger 20–28 × 18–24 mm, ovate to elliptic, smallest one 18−24 × 9−14 mm, obovate or elliptic, outer surface glabrous; ovary 10–25 × 5–7 mm, cylindrical or ellipsoid, wings 3, subequal, base rounded, apex rounded to truncate, widest point up to 12 mm (apically or subapically), glabrous, locules 3, placentation axile, placentae bilamellate; style ca. 6.5 mm long, basally fused, 3–branched, each stylodium bifurcate in the stigmatic region, stigmatic surface a spirally twisted papillose band, orange. Fruit: dry capsule; peduncles 15−75 mm long; pedicels 10–30 mm long, pale green, glabrous; seed-bearing part (8−)10−25 × 6−10 mm (excluding the wings), ovoid to ellipsoid, wing shape as for ovary, pale green or reddish green, glabrous. Seeds barrel-shaped, ca. 0.3 mm long.

Distribution:— Indonesia, endemic to Sulawesi: South and Central Sulawesi ( Fig. 1C ).

Habitat:— Lowland to hill rain forest; growing in crevices of limestone rock, terrestrially at the base of limestone cliffs and hills, or on mossy granite rocks; partially shaded to open areas at ca. 200‒900 m elevation.

Notes:— In the original description, W.S. Hoover 885 (BO) was designated as holotype ( Wiriadinata 2013: 45), and no isotypes or other additional material were indicated. Specimens with the specified collection number could not be located in BO, but six sheets indicating ‘W.S. Hoover, H. Wiriadinata, T. & M. Hoover’ as collectors, ‘889’ as the collection number, and the same locality and collection date as specified in the original description were present. The collection number ‘885’ in the original description was probably a simple clerical error, but there are six herbarium sheets present in BO that are not labelled with sheet numbers, and there is no additional information on barcodes identifying the holotype in the original description. Consequently, we designate one of the six sheets of W.S. Hoover et al. 889 as a lectotype here. All sheets have flowering material, but the sheet stamped BO-1454234 is the only one that has both male and female flowers.

Begonia hooveriana was originally described from a single collection from a heavily disturbed limestone habitat in the centre of the city of Makale ( Wiriadinata 2013). Several other collections from South and Central Sulawesi show characters that link them to B. hooveriana : a similar erect or ascending growth habit and well-developed greyishbrownish periderm on older stems ( Fig. 4A, C ); relatively large, glabrous stipules with relatively short apical bristle ( Fig. 4D ); relatively large male flowers in subumbellate partial inflorescences ( Fig. 4 E-G); and a ovary and fruit wing attachment frequently conspicuously below the base of the seed-bearing part ( Fig. 4E, I ). However, there is considerable morphological heterogeneity among these collections, e.g. leaf laminas are sometimes succulent and relatively small in plants growing in limestone rock crevices and sun-exposed habitats (e.g., Thomas & Ardi 09-101), but much larger and thinner leaf laminas can be found in other populations growing in soil or more shaded habitats (e.g., Thomas & Ardi 09-100); male partial inflorescences can be sometimes subsessile ( Fig. 4F ), but in most individuals they are borne on peduncles up to 4 cm long ( Fig. 4E ); material from the type locality has ovaries that are relatively long and have a cylindric seed-bearing part, the wing attachment is considerably below the base of the seed-bearing part, and stigma branches are rather compact ( Fig. 4I ), while in other collections the ovary is much shorter and ellipsoid, the wing attachment is just below the seed-bearing part, and the stylodia are more elongated (e.g., Thomas & Ardi 09-100) ( Fig. 4H ). Most of this variability seems to be in a morphological continuum, however, and further investigations are needed to evaluate whether meaningful segregates can be identified. Moreover, some of the observed variability may be the result of introgression with sympatrically occurring species (e.g., B. siregarii Ardi & D.C.Thomas [Ardi et al. 2014: 263]), and this aspect requires further investigation ideally employing a population genetic approach. Plants cultivated at Bogor Botanic Gardens from material collected at the type locality regularly flowered and developed mature-sized male flowers that, however, were always abscised before opening. This dropping of male flowers before opening may be an indicator of a hybrid origin (Dewitte et al. 2011).

Begonia hooveriana has been observed to be locally cultivated as outdoor ornamental plant in South Sulawesi.

Provisional IUCN conservation assessment:— Vulnerable (VU) B1ab(iii),B2ab(iii). This species has been collected at several localities in South and Central Sulawesi. The collections from Central Sulawesi are in legally protected areas (Wera Forest Reserve and Lore Lindu National Park), but the majority of collections are from South Sulawesi from localities that are within or in close proximity to settlements and agricultural land. Some of the collection localities in the Enrekang Karst and Tanah Toraja were heavily disturbed. This species is able to cope with a certain degree of habitat disturbance, but because of its fragmented distribution, the reduction of lowland and hill forest habitats in South and Central Sulawesi (Cannon et al. 2005, 2007), and the small EOO (ca. 3,100 km 2) and AOO, we assess this species as Vulnerable.

Additional specimens examined:— INDONESIA. Sulawesi. Central Sulawesi: Wera Waterfall, near Parampadende , 1 June 1979, M.M.J.v. Balgooy 3619 (A, K) ; Pakuli, Biromaru, Donggala , 25 May 2002, Ramadanil et al. RP 805 ( CEB) ; Pakuli, Maleo nesting ground, near Gumbasa River , 11 May 2007, Ramadanil Pitopang & Sylva PC UNTAD, RP 2046 ( CEB) ; Saluki, Maleo nesting ground, 29 July 2018, W.H. Ardi et al. WI 249 ( BO, SING, KRB) ; Sigi, Wera waterfall, 10 Aug. 2018, W.H. Ardi et al. WI 317 ( BO, FIPIA, KRB, SING) . South Sulawesi: Pasoei , 17 june 1929. G.K. Kjellberg 1396 ( BO) ; near Central Park Makele , 3 Sep. 1998, W.S. Hoover et al. 889 ( BO [6 sheets]) ; Buntu area, Kpg Lokkok , 15 Nov. 2003, J. Vermeulen 2299 (L, SING) ; cultivated at Bali Botanic Gardens (material collected in Tanah Toraja, Makale ), 16 May 2008, D.C. Thomas & W.H. Ardi 08-82 (E) ; Tanah Toraja, close to Makale , 29 Apr. 2009, D.C. Thomas & W.H. Ardi 09-100 ( BO, E) ; Tanah Toraja, close to Makale , 29 Apr. 2009, D.C. Thomas

& W.H. Ardi 09-101 (BO, E); Bambapuang Karst, 3 Nov. 2018, W.H. Ardi 323 ( BO, KRB, SING) ; Bambapuang Karst, 3 Nov. 2018, W.H. Ardi 325 ( BO, KRB, SING) ; Karst Baroko, Enrekang, 5 Nov. 2018, W.H. Ardi 337 ( BO, KRB, SING) ; Karst Benteng Alla, Enrekang, 5 Nov. 2018, W.H. Ardi 338 ( BO, KRB, SING) ; Gandang Batu, Toraja, 5 Nov. 2018, W.H. Ardi 339 ( BO, KRB, SING) ; Pemandian Tilangnga, 8 Nov. 2018, W.H. Ardi 348 ( BO, KRB, SING) ; Londa, Torajan Tomb, 8 Nov. 2018, W.H. Ardi 350 ( BO, KRB, SING). Cultivated material: cultivated at Brooklyn Botanic Gardens, 22 Apr. 2004, P. Harwood 126 ( BKL) ; cultivated at Brooklyn Botanic Gardens , 26 Jun 2007, M.C. Tebbitt s.n. ( BKL) .

Figures

FIGURE 1. Distribution maps of Begonia species occurring on the southwestern arm of Sulawesi or the Selayar Islands (georeferenced specimen data from major collections [B, BO, E, K, KRB, L, SING], the Begonia Resource Center [Hughes et al. 2015a], as well as some additional confirmed observations). Grey lines indicate 1° graticules.

FIGURE 4. Begonia hooveriana. A: Habit. B: Habit, in partially shaded habitat. C: Habit, growing in crevice of limestone rock in sunexposed habitat. D: Stipule; scale bar = 1 cm. E: Inflorescence and young infructescence; scale bar = 3 cm. F: Subsessile male partial inflorescences, scale bar = 5 cm. G: Male flower, front view; scale bar = 2 cm. H: Female inflorescence; scale bar = 2 cm. I: Female inflorescence (material from type locality); scale bar = 2 cm. J: Ovary cross-section, bilamellate placentation, scale bar = 3 mm. A, F, I: D.C. Thomas & W.H. Ardi 08-82; B, D, G, H: D.C. Thomas & W.H. Ardi 09-100; C, E: W.H. Ardi 323. Photos: D.C. Thomas & W.H. Ardi.