Begonia korthalsiana Miq. ex M.Hughes, 2015

Hughes, Mark, Girmansyah, Deden & Ardi, Wisnu Handoyo, 2015, Further discoveries in the ever-expanding genus Begonia (Begoniaceae): fifteen new species from Sumatra, European Journal of Taxonomy 167, pp. 1-40 : 21-23

Begonia korthalsiana Miq. ex M.Hughes sp. nov. § Reichenheimia

urn:lsid:ipni.org:names:77151645-1

Figs 4 , 10

Diagnosis

The red, fleshy bristles at the petiole apex are an unusual character in Asian Begonia and demonstrate an alliance of this species with B. sublobata Jack ( Jack 1822) and B. fluvialis sp. nov.; B. korthalsiana sp. nov. differs considerably from both in its larger, unlobed ovate-orbicular leaves (18–24 × 15–20 cm, c. 12 × 12 cm in B. sublobata ) and much larger inflorescences (c. 60 cm long with c. 100 flowers vs. c. 15 cm long with c. 30 flowers in B. sublobata ). The male flowers were described from sketches made by Irmscher in Berlin; the material is sparse and whether the flowers consistently have 2 tepals needs confirmation; the smaller size of the female flowers is probably due their immaturity.

Etymology

Named after the Dutch botanist Pieter W. Korthals [1807–1892] who was the first person to collect this species, with the specimens being later annotated by Miquel. The specimens collected by Beccari were chosen as the type as they had better fruiting material.

Type

SUMATRA: West Sumatra, Padang, Kayu Tanam, 130 m, Sep. 1872, Beccari PS857 (holo-: L [no. 898195], iso-: L, FI [3], B [3]).

Additional material

SUMATRA: Korthals s.n. ( L [4]).

Description

Large erect acaulescent herb to 60 cm tall; stem a thick woody rhizome, internodes 0.5–1 cm long. Stipules persistent, glabrous, 25–30 mm long, lanceolate, with a filiform extension at the apex. Leaves: petiole 29–34 cm long, cross-section unknown, glabrous, with a semicircle of 10–15 stiff red c. 8 mm long bristles at the apex; lamina ovate-orbicular, asymmetric, 18–24 × 15–20 cm, basifixed, base cordate with lobes overlapping, sinus depth 20–30 mm, upper and lower surface glabrous, venation palmate; margin broadly crenate and denticulate, with recurved stiff teeth at the end of the veins; apex shortly acuminate. Inflorescences axillary, total length 50–60 cm, cymose, branching 4–6 times, many flowered, bisexual; primary peduncle 40 cm long, glabrous; bracts caducous, unknown. Male flowers: pedicel 15 mm long; tepals 2, orbicular, 11 × 12 mm, slightly cordate at the base, margin entire; androecium globose, with 80–100 stamens; filaments subequal, 1.5 mm long, fused at the base into a short column; anthers slightly shorter than the filament, oblong elliptic, connective slightly retuse, slightly hooded, dehiscing through slits running nearly the entire length of the anther, the slits positioned on the outer face of the anther. Female flowers: pedicel 11 mm long; ovary glabrous, 6 × 10 mm including wings; capsule elliptic, 5 × 3 mm, 3 locular, placentae entire; wings 3, subequal, rounded triangular; tepals 2, orbicular, 6 × 5 mm, margin entire; styles 3, stigmatic surface once spirally twisted, caducous. Fruit recurved on a 2–2.5 cm pedicel; wings subequal, rounded-triangular, 12 × 18 mm in total; capsule elliptic, 9 × 6 mm, glabrous; apex obtuse.

Distribution and habitat

Frustratingly Korthals did not give a precise locality for his collection, which is the only other collection of this species apart from the type. Although he did visit Kayu Tanam (“Kajoetanam”) on April 25 th 1834, where Beccari made his collection of this species, Korthals also visited many other locations in Sumatra. The species is likely endemic to Kayu Tanam in West Sumatra near Padang ( Fig. 4 ).

Conservation status

As 140 years have passed since the last collection of this species, it seems reasonable to assume it is a very local and scarce endemic of low-altitude forest. As Kayu Tanam is now a mix of suburban and agricultural areas on the main road between Padang city and Padangpanjang, it is possible that B. korthalsiana is extinct. However there are still expanses of forest that need exploring between Kayu Tanam and Lake Singkarak before this is declared; until then we assess B. korthalsiana to be Data Deficient ( IUCN 2012).

Figures

Fig. 4. Map of Sumatra showing the full known species distributions based on collection localities. Each point may represent more than one collection.

Fig. 10. Begonia korthalsiana Miq. ex M.Hughes sp. nov. A. Infructescence on isotype Beccari PS857 (FI). B. Male flower with pedicel (left), tepal of male flower (right). C. Androecium (left), anther (right). D. Rhizome and leaf. E. Anther. F. Leaf lamina underside at point of petiole attachment showing fleshy bristles. B, C drawn by E. Irmscher from isotype Beccari PS857 (B); D–F drawn by M. Hughes from isotype Beccari PS857 (FI).