E D I N B U R G H J O U R N A L O F B O T A N Y 71 (2): 259–268 (2014)
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© Trustees of the Royal Botanic Garden Edinburgh (2014)
doi:10.1017/S0960428614000092
TWO NEW SPECIES OF BEGONIA
(BEGONIACEAE) FROM SULAWESI, INDONESIA
W . H . A R D I 1, I M A D E A R D A K A 2, H A R T U T I N I N G S I H 1,
I NYOMAN LUGRAYASA2 & D. C. THOMAS3
Two new species of Begonia (Begoniaceae), Begonia gambutensis Ardi & D.C.Thomas
and Begonia siregarii Ardi & D.C.Thomas, are described from material collected on the
Indonesian island of Sulawesi. Both species belong to Begonia section Petermannia.
A key to the species in the provinces North Sulawesi and Gorontalo is provided.
Keywords. Begonia, new species, Sulawesi.
INTRODUCTION
Begonia L. (Begoniaceae), with more than 1550 species, is one of the largest genera of
angiosperms (Hughes, 2008). One hotspot of species diversity lies in Malesia, where
around 450 species have been described (Hughes, 2008; Thomas et al., 2012). Recent
expeditions to the Indonesian island of Sulawesi have resulted in the description of 22
new Begonia species since 2006 (Hughes, 2006; Thomas & Hughes, 2008; Girmansyah
et al., 2009; Thomas et al., 2009a,b, 2011; present study), raising the number of currently accepted species from the island to 44 (Thomas et al., 2013). This recent high
discovery rate of Sulawesi Begonia species reflects the past under-exploration of the
island, which has the lowest collection density of the larger islands in Indonesia
(Cannon et al., 2007).
Several species of Begonia which were collected on expeditions to North and South
Sulawesi organised by Bogor and Bali Botanic Gardens were brought into cultivation
at Bali Botanic Garden. From these collections, two species, Begonia guttapila
D.C.Thomas & Ardi and B. didyma D.C.Thomas & Ardi, have been recently described
(Thomas et al., 2009b), and two more are newly described here. Like the vast majority
of Sulawesi Begonia species, these two new species are placed in Begonia section
Petermannia, as they exhibit typical characters of the section: protogynous inflorescences, two-flowered female inflorescences, three-locular ovaries with bilamellate
placentae, and anthers with unilaterally positioned slits (Doorenbos et al., 1998).
A key to the Begonia species of North Sulawesi and Gorontalo provinces is provided
1
2
3
Bogor Botanic Garden, Jl. Ir. H. Juanda No. 13, PO Box 309, Bogor, Indonesia. E-mail for correspondence:
wisnu.handoyo.ardi@lipi.go.id
Bali Botanic Garden, Candikuning, Baturiti, Tabanan 82191, Bali, Indonesia.
Naturalis Biodiversity Center, Leiden, PO Box 9514, 2300 RA Leiden, The Netherlands. E-mail: Daniel.
Thomas@naturalis.nl
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to complement the key to the species of South and West Sulawesi provinces in Thomas
et al. (2011).
All available Begonia specimens from B, BM, BO, E, K, L, SING and WAG have
been consulted and hence it must be assumed, at least until more intensive collecting
in Sulawesi reveals otherwise, that both species described here have very restricted
ranges (Fig. 1).
SPECIES DESCRIPTIONS
Begonia gambutensis Ardi & D.C.Thomas, sp. nov. Sect. Petermannia.
Differs from other Sulawesi Begonia species by the character combination of a
dense crimson indumentum on vegetative parts, male inflorescences showing
basal dichasial branching with well-developed internodes and distal monochasial
branching, and female flowers with obovate tepals distinctly tapering towards the
base. – Type: Cultivated in Bali Botanic Garden from vegetative material collected
in the wild (Indonesia, Sulawesi, Gorontalo, Bone Bolango district, Suwawa Timur
subdistrict, Gunung Gambuta, Desa Pinogu, side of river, c.700 m), 3 ix 2013, D.C.
Thomas & W.H. Ardi 13-802 (holo BO; iso E, L). Figs 1, 2.
Perennial, monoecious herb with erect stems, to c.60 cm tall, with a dense indumentum of crimson, multicellular, simple trichomes up to c.1.2 mm long and a sparse
indumentum of microscopic, glandular trichomes on stems and leaves. Stems
branched; internodes c.3–5.5 cm long, reddish. Leaves alternate; stipules caducous,
8–17 × 6–7 mm, asymmetric, oblong to narrowly elliptic, with a slightly prominent
midrib abaxially projecting up to c.2 mm at the apex; petioles c.4–9 cm long, red;
lamina basifixed, 7–12.6 × 4.8–8 cm, asymmetric, ovate to elliptic, base cordate, lobes
sometimes overlapping, apex acuminate, margin serrate to biserrate, undulate, the
teeth long bristle-pointed, adaxial surface midgreen and abaxial surface pale green,
primary veins 5–8, actinodromous, secondary veins craspedodromous. Inflorescences:
protogynous; female inflorescences 2-flowered, one node basal to the male inflorescences or solitary, peduncles 4–7 mm long; male inflorescences distal to the female
inflorescences or sometimes solitary, usually branched with 2–3 cymose partial inflorescences, each showing 1–2 basal dichasial branchings and several distal monochasial branchings, the internodes well developed in the basal part, but condensed in the
most distal part. Male flowers: pedicels 9–15 mm long; tepals 2, pink, rarely white,
9–16 × 13–21 mm, broadly ovate, base slightly cordate, margin fringed by stiff hairs,
apex rounded, abaxially hairy; androecium of c.40–60 stamens, yellow, filaments up to
c.1.5 mm long, slightly fused at the very base, anthers up to c.1 mm long, obovate,
dehiscing through unilaterally positioned slits > 1/2 as long as the anthers. Female
flowers: pedicels 3–4 mm long; tepals (4–)5, whitish-pinkish, unequal, the smallest
8–14 × 5–7 mm, obovate, the larger 21–22 × 15–18 mm, obovate to elliptic, the margin serrulate and fringed with short stiff hairs, abaxially hairy; ovary ellipsoid, hairy,
locules 3, placentation axile, placentae bilamellate, wings 3, subequal, narrowly
TWO NEW SPECIES OF BEGONIA FROM SULAWESI
261
F I G . 1. Distribution map. Collection sites are indicated by a square (Begonia gambutensis,
based on georeferencing the locality ‘Desa Pinogu’ using the GeoNames geographical database
at http://www.geonames.org/) and a circle (Begonia siregarii, based on GPS data). Topographical
variation is indicated by five shades of grey: 0–500 m (the lightest shade), 500–1000 m,
1000–1500 m, 1500–2000 m, and > 2000 m (the darkest shade).
triangular, base rounded, apex truncate, the margin serrulate with teeth extended into
multicellular hairs up to c.1 mm long, styles basally fused, 3-branched, each stylodium bifurcate in the stigmatic region, stigmatic surface a spirally twisted papillose
band, orange. Fruits: peduncles c.9–13 mm long; pedicels 5–7 mm long; ellipsoid,
14–16 × 5–7 mm (excluding the wings), sparsely to moderately densely hairy, dehiscent, splitting along the wing attachment, wing shape as on ovary, 9–11 mm wide
at the widest point (at the apex); seeds ellipsoidal, c.0.3–0.4 mm long, collar cells
c.1/5–1/4 of the length of the seed.
Distribution. Indonesia, endemic to Sulawesi, Gorontalo.
Habitat. Primary rain forest, forest floor at the side of a river, at c.700 m above sea
level.
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F I G . 2. Begonia gambutensis Ardi & D.C.Thomas. A, habit; B, abaxial leaf surface; C, stipule;
D, inflorescence; E, male flower; F, female inflorescence; G, female flower, front view;
H, ovary, cross-section, three-locular with axile, bilamellate placentae; I, fruit. A–I: D.C.
Thomas & W.H. Ardi 13-802. Scale bars: B = 7 cm; C = 7 mm; E = 18 mm; F = 12 mm; G = 15 mm;
H = 3 mm; I = 12 mm.
TWO NEW SPECIES OF BEGONIA FROM SULAWESI
263
Etymology. The epithet ‘gambutensis’ refers to Gunung Gambuta, where the type
material was collected.
Additional specimen examined. SULAWESI. Gorontalo: Gunung Gambuta (cultivated at Bali
Botanic Garden from material collected in the wild), 4 iv 2009, D.C. Thomas & W. Ardi 09-53
(BO, E).
The complex inflorescence architecture of Begonia gambutensis with basal dichasial
branching with well-developed internodes and distal monochasial branching (Fig. 2D)
in combination with the crimson indumentum on vegetative parts (Fig. 2C), and
tepals of the female flowers which conspicuously taper towards the base, separates
this species from other Sulawesi Begonia species.
In molecular phylogenetic analyses on the basis of non-coding plastid DNA data,
Begonia gambutensis (accession DCT 09-53) is retrieved in a well-supported clade
with the Northern Sulawesi species B. macintyreana and B. chiasmogyna, which is
sister to a clade containing the Northern Sulawesi species B. mendumiae, B. capituliformis, B. hispidissima and B. masarangensis (Thomas, 2010; Thomas et al., 2012).
The complex, many-flowered inflorescences of Begonia macintyreana, which show
well-developed internodes as well as basal dichasial branching and distal monochasial
branching, are similar to the ones found in B. gambutensis. However, apart from the
inflorescence architecture the two species are morphologically dissimilar and the
glabrous stems, leaves and generative parts and the somewhat pointed apices of the
tepals of Begonia macintyreana separate this species from B. gambutensis. Begonia
chiasmogyna has some similarity with Begonia gambutensis with regard to the dense
indumentum on vegetative parts, the complex inflorescence architecture with relatively well-developed internodes, and the tepals of the female flowers, which taper
conspicuously towards the base (Hughes, 2006). However, Begonia chiasmogyna can
be easily differentiated from B. gambutensis by the colour of the indumentum (white,
not reddish), as well as the number and shape of the tepals of the female flowers (four
obtrullate tepals versus five obovate tepals).
Begonia siregarii Ardi & D.C.Thomas, sp. nov. Sect. Petermannia.
Similar to Begonia prionota D.C.Thomas & Ardi. Differs from this species by its
dentate-denticulate leaf margins (biserrate to shallowly lobed in B. prionota), the
longer peduncles of the female inflorescences (2.2–4 cm vs. 1.2–2 cm), more strongly
condensed monochasia, and entire tepals of the female flowers (irregularly serrate
in B. prionota). – Type: Cultivated in Bali Botanic Garden from vegetative material
collected in the wild (Indonesia, Sulawesi, South Sulawesi, Tana Toraja, Kete Kesu
village, burial site, 02°59′53.1″S, 119°54′35.3″E, 800 m), 3 ix 2013, D.C. Thomas &
W.H. Ardi 13-801 (holo BO; iso E, L). Figs 1, 3.
Perennial, monoecious herb with erect stems, to c.1 m tall, with a moderately dense to
dense indumentum of white, multicellular, simple trichomes up to c.0.5 mm long and
a sparse indumentum of microscopic, glandular trichomes on stems and leaves. Stems
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F I G . 3. Begonia siregarii Ardi & D.C.Thomas. A, habit; B, abaxial leaf surface; C, stipule;
D, inflorescence; E, male flower; F, female inflorescence; G, female flower, front view; H, ovary,
cross-section, three-locular with axile, bilamellate placentae; I, fruit. A–I: D.C. Thomas & W.H.
Ardi 13-801. Scale bars: B = 10 cm; C = 8 mm; E = 16 mm; F = 12 mm; G = 15 mm; H = 3 mm;
I = 12 mm.
TWO NEW SPECIES OF BEGONIA FROM SULAWESI
265
branched; internodes c.6.5–10.5 cm long, reddish to green. Leaves alternate; stipules
caducous, 10–21 × 6–10 mm, slightly asymmetric, ovoid to elliptic, with an abaxially
slightly prominent midrib projecting up to 5 mm at the apex; petioles 4–14 cm long,
reddish; lamina basifixed, 7.5–23.5 × 4–14 cm, strongly asymmetric, ovate to elliptic,
base cordate and lobes sometimes slightly overlapping, apex acute, margin irregularly
and distantly dentate and denticulate between the larger teeth, the teeth long bristlepointed, adaxial surface dark green and abaxial surface pale green, primary veins 8–10,
actinodromous, secondary veins craspedodromous. Inflorescences: protogynous;
female inflorescences 2-flowered, one node basal to male inflorescences; peduncles
2.2–4 cm long; male inflorescence branched and composed of 3–5 cymose partial
inflorescences, each showing (0–)1–3 basal dichasial branchings and several distal
monochasial branchings, the internodes well developed in the basal part, but strongly
to moderately condensed in the distal part; peduncles of partial inflorescences c.9–31 mm
long. Male flowers: pedicels 23–28 mm long; tepals 2, white or white tinged with pink,
cream coloured or cream coloured tinged with pink when young, 15–19 × 15–22 mm,
broadly ovate to suborbicular, base slightly cordate, margin entire, apex rounded,
abaxially with a sparse indumentum or glabrescent; androecium of c.50–90 stamens,
yellow, filaments up to c.2 mm long, slightly fused at the very base, anthers up to c.1 mm
long, obovate, dehiscing through unilaterally positioned slits > 1/2 as long as the
anthers. Female flowers: pedicels 10–20 mm long; tepals 5, white tinged with pink,
unequal, the smallest 14–27 × 6–8 mm, ovate to elliptic, the larger ones 18–29 ×
10–20 mm, elliptic to oblong, the margin entire, sparsely to moderately hairy or almost
glabrous; ovary ellipsoid, hairy, locules 3, placentation axile, placentae bilamellate,
wings 3, equal, base rounded, apex truncate, margin entire, styles basally fused,
3-branched, each stylodium bifurcate in the stigmatic region, stigmatic surface a
spirally twisted papillose band, yellow. Fruits: pedicels 10–20 mm long; ellipsoid,
10–16 × 5–7 mm (excluding the wings), sparsely to moderately hairy to glabrescent,
wing shape as on ovary, 5–10 mm wide at the widest point (at the apex); seeds ellipsoidal, c.0.4–0.5 mm long, collar cells c.1/5–1/4 of the length of the seed.
Distribution. Indonesia, endemic to Sulawesi, South Sulawesi.
Habitat. Strongly disturbed secondary forest, forest floor, limestone, collected at
c.800 m above sea level.
Etymology. The species is named in honour of the former director of Bogor Botanic
Gardens, Mr Mustaid Siregar, who collected living material of this species in 2007.
Additional specimens examined. SULAWESI. South Sulawesi: Tanah Toraja, Kete Kesu burial site,
4 iv 2009, D.C. Thomas & W. Ardi 09-51 (BO, E); ibid., 15 vi 2013, Rismita Sari RI 1367 (BO).
The male inflorescence architecture (Fig. 3D) in combination with the long peduncles
of the female inflorescences (2.2–4 cm long) (Fig. 3F) and the moderately dense to
dense indumentum of relatively short (up to c.0.5 mm), white hairs on stems and
leaves (Fig. 3C, I) differentiate this species from other Sulawesi Begonia species.
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Among Sulawesi Begonia only B. prionota D.C.Thomas & Ardi shows a similar character combination. The male partial inflorescences are more condensed in Begonia
siregarii, however, and the length of the peduncles of the female inflorescences, the
dentate-denticulate leaf margins and entire tepals of the female flowers further differentiate B. siregarii from B. prionota, which shows shorter peduncles (c.1.2–2 cm),
biserrate to shallowly lobed leaf margins and characteristic irregularly serrate tepal
margins.
In molecular phylogenetic analyses on the basis of non-coding plastid DNA data,
Begonia siregarii (accession DCT 09-51) is nested in a clade with other species from
Central and South Sulawesi, including B. ozotothrix D.C.Thomas, B. nobmanniae
D.C.Thomas & Ardi, B. didyma, B. prionota and material of some undescribed species
(Thomas, 2010; Thomas et al., 2011). Begonia didyma and B. nobmanniae are smallerleaved and relatively delicate plants vegetatively highly dissimilar to the much more
robust B. siregarii. Begonia ozotothrix can readily be distinguished by the very short
peduncles (1–5 mm) and pedicels (1–4 mm) of the female inflorescences and flowers,
respectively, as well as the strongly condensed male partial inflorescences.
Key to Begonia in North Sulawesi and Gorontalo provinces
1a. Plants rhizomatous, creeping or decumbent, < 25 cm in height
1b. Plants erect, or if decumbent or arching > 25 cm in height
2
4
2a. Plants rhizomatous; ab- and adaxial leaf surfaces with long, erect trichomes
Begonia mendumiae M.Hughes
2b. Plants creeping or decumbent, not rhizomatous; ab- and adaxial leaf surfaces
glabrous, or abaxial surface with sparse, strigose indumentum
3
3a. Leaf margin unevenly dentate; pedicels of fruits > 10 mm
Begonia heteroclinis Miq. ex Koord.
3b. Leaf margin shallowly lobed; pedicels of fruits < 10 mm
Begonia gemella Warb. ex L.B.Sm. & Wassh.
4a. Leaves pinnatisect to bipinnatisect
Begonia humilicaulis Irmsch.
4b. Leaves entire or lobed no more than halfway to the midrib
5
5a. Female inflorescences 1- or 2-flowered, separated from the male inflorescences by
at least one internode; fruit dry and dehiscent
6
5b. Female and male flowers occurring together in bisexual cymose inflorescences
with > 2 female flowers; fruit fleshy and indehiscent
14
6a. Petioles short (up to 10 mm), leaves long and narrow (c.5–12 × 1.5–3.1 cm, length/
width ratio > 3:1)
Begonia cuneatifolia Irmsch.
6b. Petioles usually longer than 10 mm; leaf length/width ratio < 3:1
7
7a. Male inflorescences subumbellate, i.e. consisting of strongly condensed cymes
with internodes < 1 mm long
Begonia capituliformis Irmsch.
TWO NEW SPECIES OF BEGONIA FROM SULAWESI
267
7b. Male inflorescence not subumbellate, showing dichasial or monochasial branching with at least the basal internodes > 1 mm long
8
8a. Female flowers with 4 tepals
8b. Female flowers with 5 tepals
Begonia chiasmogyna M.Hughes
9
9a. Wings on ovary and fruit < 6 mm at the widest point
9b. Wings on ovary and fruit > 6 mm at the widest point
10
11
10a. Leaves c.7–11 × 3–6 cm, margin irregularly dentate to serrate
Begonia hispidissima Zipp. ex Koord.
10b. Leaves 4.9–6.6 × 1.8–3 cm, margin irregularly incised up to about halfway to the
midrib
Begonia masarangensis Irmsch.
11a. Male inflorescences with < 6 flowers
11b. Male inflorescences with > 8 flowers
Begonia strachwitzii Warb. ex Irmsch.
12
12a. Plants with sparse indumentum of microscopic glandular hairs and dense indumentum of multicellular, simple trichomes on stems and leaves
Begonia gambutensis Ardi & D.C.Thomas
12b. Plants glabrous except for microscopic glandular hairs
13
13a. Petioles < 2.6 cm long; peduncles of female inflorescences < 5 mm long
Begonia insularum Irmsch.
13b. Petioles 4–7 cm long; peduncles of female inflorescences 10–15 mm long
Begonia macintyreana M.Hughes
14a. Leaves oblong-lanceolate; male flowers with 4 tepals
Begonia aptera Blume
14b. Leaves broadly ovate; male flowers with 2 tepals
Begonia rieckei Warb.
ACKNOWLEDGEMENTS
We are grateful to the curators of B, BM, BO, E, K, L, SING and WAG for allowing
us access to herbarium material and living collections; to Ms Rismita Sari for collecting
additional living material of Begonia siregarii; to Mr I Wayan Warnatea (Bali Botanic
Garden) who collected the material of Begonia gambutensis; and to the horticulture
staff at Bali Botanic Garden and Bogor Botanic Gardens. The support of D.C.T.’s
research on Begonia by the M.L. MacIntyre Trust is gratefully acknowledged.
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Received 18 September 2013; accepted for publication 18 February 2014