Begonia yenyeniae J.P.C.Tan, 2018

Tan, Joanne Pei-Chih, Tam, Sheh May & Kiew, Ruth, 2018, Begonia yenyeniae (Begoniaceae), a new species from Endau Rompin National Park, Johor, Malaysia, PhytoKeys 110, pp. 23-37 : 23

Begonia yenyeniae J.P.C.Tan sp. nov. Figure 2

Section.

Jackia M.Hughes

Diagnosis.

Similar to Begonia rajah Ridl. (1894:213) in its handsome leaves, striking brownish-pink to brownish-red with greenish-yellow veins in young leaves becoming bronzy variegation at maturity; in its creeping growth habit, number of tepals in male (4 tepals) and female flowers (3), palmate leaf venation and many-flowered cymes, but several notable characters distinguish the new species, including its orbicular-reniform leaf blades (vs. subrotund with an abruptly acute apex in B. rajah ), smaller stipules, 9-12 × 3-4 mm, three times longer than wide (vs. 15-20 × 10-12 mm, less than twice as long as wide), smaller ovate or obovate bracts 2-3 × 1.5-2 mm (vs. bracts bowl-shaped, wide ovate, 5-8 × 7.5-8 mm), margin shallowly crenate (vs. margin angular), bullate leaf surface (vs. conspicuously pronounced bullate). Furthermore, the leaf colour of cultivated B. rajah is more vivid and, in contrast, its tepals, stipules and bracts are also a deeper shade of pink, compared to those of B. yenyeniae .

It is also similar to B. reginula Kiew (2005: 218) in its habit, leaf colour, less pronounced bullate blade, palmate venation, bracts, ovary with 3 equal wings of similar shape, but B. yenyeniae is different in its relatively smaller and narrower tepals 5-7 × 6 mm (vs. 6-10 × 9-11 mm in B. reginula ), 3 in male or 4 tepals in female flowers (vs. 2 tepals in both male and female flowers) and rounded base (vs. subcordate), stipules with prominently keeled (vs. keel absent), and apex rounded (vs. apex attenuate).

Although molecular data indicate a close relationship to B. foxworthyi ((1925: 311), the latter species is morphologically distinct in its conspicuously oblique leaf with an acute to acuminate apex (vs. orbicular-reniform with a rounded apex), its entire margin (vs. crenate) and plain green, non-bullate leaf surface (vs. purplish-green to brownish-purple and bullate) and its male flowers with 2 tepals (vs. 4 tepals). In addition, it usually grows on limestone substrates (vs. confined to granite substrates.

Type.

Peninsular Malaysia. Johor, Mersing, Endau-Rompin National Park, Sungai Selai, 14 April 2018, Kiew FRI 81950 (holotype E!; iso-: K!, SAR!, SING!).

Description.

Lithophytic herb with rhizomatous stem. Indumentum of soft hairs, usually cream- coloured, sparse on stipules (mostly on the keel and 0.5-1.5 mm long), petioles more densely hairy towards blade (2-3 mm), leaf margin (hairs ca. 1 mm) and veins beneath (ca. 1 mm) but sparse (ca. 0.5 mm) or absent on ventral surface of outer tepals and on peduncle hairs hardly visible to the naked eye. Stems creeping, apex usually slightly erect, branched, 5-9 mm thick, light yellowish-green; stipules 3 per node, two triangular, abruptly narrowed to an attenuate apex terminating in a hair, keeled from base to apex, margin entire and translucent, 9-12 × 3-4 mm, pale yellowish-green, one narrowly lanceolate, ca. 3 mm long, persistent. Leaves tufted, alternate, 2-3 mm apart; petioles terete, 2.5-3.5 mm across, up to 12.5 cm long, pale brownish-pink to darker pink towards blade; blades thinly succulent, glabrous, orbicular-reniform, asymmetric, 8-11.5 × 9.5-13.5 cm, scarcely angular, margin somewhat crenate with acute teeth bent abruptly downwards between teeth, ciliate, basal lobes cordate, overlapping when mature, moderately raised between veins, light purplish-green to dull brownish-purple, young blades brownish-pink to brownish-red, paler beneath; veins palmate, slightly prominent towards the base but impressed where branched towards the margin, prominent beneath, lateral veins ca. 2-3 pairs, greenish-yellow when young and whitish-green when mature. Inflorescences axillary, more or less erect, 10-23 cm long, brownish-red, peduncles 8-18.5 cm long, two main branches 2-3 cm long, pedicels 6-9 mm; bracts in pairs at node of peduncle, glabrous, elliptic-ovate or obovate, margin towards apex laciniate, 2-3 × 1.5-2 mm, light yellowish-green sometimes with a faint tinge of pink, persistent. Male flowers with 4 tepals, margin entire, 1-1.2 × 1.1-1.4 cm; outer 2 tepals rotund, concave at centre, 5-7 × 6 mm, pale greenish-white or light pink or pale pinkish-white, inner 2 tepals obovate, apex rounded or sometimes retuse and impressed along centre, ca. 5 × 3 mm, white; stamens numerous, torus ca. 1 mm long, stamen mass globose, symmetric, ca. 2.5 mm across; anthers obovoid-oblong, tip emarginate, ca. 0.5 mm long, dehiscing through 2 longitudinal slits. Female flowers with a light yellowish-green ovary sometimes with faint light pink tinge, ca. 5.5 × 9 mm, locules 3, wings 3 equal, placentation axile, 1 placenta per locule, each placenta usually with 2 minute branches at the base; usually tepals 3, outer 2 tepals, rotund, concave at centre, ca. 4 × 4.5 mm, white with faint green tinge; styles and stigmas 3, 1.5-2 mm, style light greenish-yellow, stigma pale yellow, papillose, spiral band. Capsules ca. 6 × 12 mm, locules 3, splitting longitudinally between locules, wing 3 equal, ca. 4 mm wide, surface glabrous, styles and stigmas persisting after tepals have fallen, dangling on a fine, thread-like pedicel ca. 5.5 mm long. Seeds numerous, barrel-shaped, 0.3-0.34 × 0.2-0.22 mm, collar cells slightly more than half the seed length, surface sculptured.

Distribution.

Endemic in Peninsular Malaysia, Johor, Mersing District, Endau-Rompin National Park, Sungai Selai. It is apparently a rare species as it is known only from the type locality in Endau Rompin National Park.

Etymology.

Named after Dr Sam Yen-Yen, Malaysian botanist, specialist in Zingiberaceae who first discovered the species and recognised its potential as an ornamental plant.

Conservation status.

Critically Endangered CR B2ab(iii, v), D1. Although the type locality is within a Totally Protected Area, it is known from only one population about 1.5 km2 and its habitat is threatened by ecotourism activity and illegal collecting. The area of observed population covers about 1.5 km2 (P.T. Ong pers. comm.).

Ecology.

In primary lowland mixed dipterocarp forest, growing on moss-covered rocks, rarely epiphytic, near a waterfall in deep shade.

Note.

The ovary of species in section Jackia have three locules, each with an unbranched placenta, but in this species two vestigial branches are present near the base of the placenta (Figure 2G ). This is also seen, but is less pronounced, in B. rajah .

Other specimens examined.

Peninsular Malaysia. Johor: Mersing, Endau-Rompin National Park, Sungai Selai, 15 Aug 2002, Sam et al. FRI 47082 (KEP!), 24 July 2012, Hairul et al. FRI 78570 (KEP!, SING!).

Figures

Figure 2. Begonia yenyeniae J. P. C. Tan, sp. nov. A Side and front view female flower B Back and front view of male flower C Stamen mass D Anthers E Habitat: moss-covered rocky slope by waterfall F Young fruit with stigma still attached G Transverse section of fruit H Seeds I Mature leaf J Upper leaf surface (moderately bullate) K Veins completely prominent on lower leaf surface L Petiole M Young blade N Stipules O-Q Upper, lower and side view of leaf margin R A pair of bracts and bracteole at peduncle and rachis; hairs scarcely on ventral surface of outer tepals. (Photographs by E Y. Y. Sam, D P. T. Ong)