Two new species of Begonia, B. moneta and B. peridoticola (Begoniaceae) from Sabah, Malaysia

Mount Kinabalu, reknowned for its high biodiversity and endemism, is a National Park in the State of Sabah on the northern end of the island of Borneo. Every year many visit the higher part of the Kinabalu National Park, while most lowland forests in the Park are under-explored. Two unknown species of Begonia were collected from a peridotic (ultramafic) cliff in the Kinabalu National Park at ca. 400 m elevation. The two species are named B. moneta C.-I Peng, Rimi & C. W. Lin and B. peridoticola Rimi, C.-I Peng & C. W. Lin. Begonia moneta (sect. Baryandra) is similar to B. gueritziana Gibbs, a widespread species of the same section in Borneo, differing in the peltate (vs. basifixed) leaves and the smaller flower parts. Also, their chromosome numbers are different (B. moneta, 2n = 30; B. gueritziana, 2n = 28). The peltate and succulent foliage of B. moneta is also reminiscent of B. burttii Kiew & S. Julia and B. payung S. Julia & Kiew, both of sect. Reichenheimia, from Sarawak. Begonia moneta is distinct from the two species in having branched (vs. entire) placental lamellae. Additionally, B. moneta differs from B. burttii in having 4 (vs. 5) tepals in pistillate flowers and markedly unequal (vs. equal) fruit wings. Begonia moneta differs from B. payung in the smaller leaves and conspicuously winged (vs. wingless) capsules. Begonia peridoticola (sect. Petermannia) resembles B. punchak Kiew & S. Julia from limestone areas in Kuching Division, Sarawak, differing in the entire leaf margin (vs. distantly dentate), much larger capsular wings (8–11 mm vs. 2–3 mm wide) and yellow, spiral (vs. crimson, U-shaped) styles. A careful study of the herbarium materials and literature supports the recognition of the two new species. Detailed descriptions, line drawings, color plates, chromsome data, foliar SEM observations and comparisons with phenetically similar species are provided to aid in identification.


Background
Mount Kinabalu, reknowned for its high biodiversity and endemism, is a National Park in the State of Sabah on the northern end of the island of Borneo (Somaweer 2007). Every year many visit the higher part of the Kinabalu National Park, while most lowland forests in the Park are under-explored. Several new species of Begonia were documented from Sabah in recent years (Reza & Kiew 1998;Beaman et al. 2001;Kiew 1998;2001;Kiew & Tan 2004). In continuation of our recent taxonomic studies on Asian Begonia (e.g. Chung et al. 2014;Ding et al. 2014;Lin & Peng 2014, Lin et al. 2014aLin et al. 2015;Nakamura et al. 2013;Peng et al. 2013Peng et al. , 2014aRubite et al. 2013Rubite et al. , 2014, we report the discovery of two new species of Begonia, B. moneta and B. peridoticola, that co-occur on a peridotic (ultramafic) cliff in the Kinabalu National Park at ca. 400 m elevation. The two species belong to different sections, and no sign of natural hybridization was apparent locally.

Chromosome preparations
Somatic chromosomes of Begonia moneta were examined using root tips from plants of the type collection. The methods of pretreatment, fixation and staining for chromosome observations followed Peng et al. (2014a). Classification of the chromosome complements based on centromere position at mitotic metaphase follows Levan et al. (1964). Voucher specimen (Peng 22343) is deposited in HAST.

Cryo scanning electron microscopy
Fresh leaves of Begonia moneta and B. peridoticola were dissected and attached to a stub. The samples were frozen with liquid nitrogen slush, then transferred to a sample preparation chamber at −160°C and etched for 15 min at −85°C. After etching, the temperature droped to −130°C for sample fracturing and coating. After coating, the samples were transferred to the SEM chamber and observed at −160°C with a cryo scanning electron microscope (FEI Quanta 200 SEM/Quorum Cryo System PP2000TR FEI). Voucher specimens (Begonia moneta: Peng 22344; B. peridoticola: Peng 22343) are deposited at HAST.  銀幣秋海棠Figures 1 and 2. Plant monoecious, epipetric, creeping, perennial. Rhizome succulent, 3.5-9 cm long, 0.3-0.4 cm across, internodes 0.2-0.6 cm, greenish to reddish brown, subglabrous.

Chromosome cytology
Somatic chromosomes at mitotic metaphase of Begonia moneta were determined to be 2n = 30 (Figure 4). Among the 30 chromosomes, two are comparatively longer (1.8-2.0 μm long) than the rest; the remaining 28 chromosomes gradually varied from 0.9 to 1.5 μm long. Several longer chromosomes were metacentric or submetacentric, however, centromere positions of shorter chromosomes could not be determined. Satellites were not observed.

Etymology
The specific epithet refers to the thick, rounded leaves that are reminiscent of coins.

Distribution and ecology
MALAYSIA. Borneo. Sabah. Kota Marudu District. Endemic in Kinabalu Park, elev. ca. 300-400 m, growing on the crevices of peridotite breccia rock face in an ultramafic area.

Etymology
The specific epithet is derived from the peridotite breccia rock face at the Bat Cave cliffs near Serinsim substation from where it was collected.

Notes
Begonia peridoticola resembles B. keithii Kiew (Kiew 1998) and B. punchak Kiew & S. Julia (Kiew & Julia 2007) in the cane-like stem and succulent leaves. Begonia keithii is endemic to limestone in the Semporna Forest Reserve in southeastern Sabah. The new species is readily distinguishable from B. keithii in the undulate, lanceolate-ovate (vs. narrowly lanceolate) leaves and cordate (vs. much prolonged) basal lobes. The new species is also similar to B. punchak from limestone areas in Kuching, Sarawak, differing in the persistent (vs. deciduous) stipules; yellow, spiral (vs. crimson, widely Ushaped) styles; and much larger capsular wings (8-11 mm vs. 2-3 mm wide).

Conclusion
A careful study of the literature, herbarium specimens and living plants, both in the wild and in cultivation, supports the recognition of the two new species. Detailed descriptions, line drawings, color plates, chromosome data, foliar SEM observations and comparisons with phenetically similar species are provided to aid in identification.