Begonia harimalalae Scherber. & Duruiss., 2019

Scherberich, David & Duruisseau, Jacky, 2019, Three new species of Begonia sect. Erminea (Begoniaceae) from north-east Madagascar, Adansonia (3) 41 (7), pp. 59-67 : 64-66

Begonia harimalalae Scherber. & Duruiss. , sp. nov.

( Fig. 4 )

Begonia harimalalae Scherber. & Duruiss. , sp. nov. can be compared to B. erminea but it differs by the much thicker, more numerous (3-8 vs 2-5) and larger (10-15 vs 4-8 cm) leaves, which are glabrous, without spiculiform hairs adaxially and with the margins shallowly and sparsely serrate vs densely biserrate.

TYPUS. — Cultivated plant in J. Duruisseau’s ( Fig. 5 ) greenhouse, [originally collected by H. Laporte in the nineties in Madagascar, Analanjirofo region: Makira forest , in the lower basin of the Voloina river , near Vodriana (or Ambodiriana) village ( Fig. 1 ), 15°32’44.5”S, 49°33’02”E, 175 m], 28.XI.2016, Scherberich 1153 (holo-, LYJB! ; iso-, P!; TAN!) .

DISTRIBUTION AND ECOLOGY. — Known only from a single collection at the eastern border of the Makira Natural Park in north-east Madagascar, in the lower basin of the Voloina river, near Vodiriana (or Ambodiriana) village, where it grows in scattered primary forest remains or old secondary forest, on rocky (gneiss) slopes, in a population with few individuals, at low elevation, around 100-200 m.

CONSERVATION STATUS. — The Makira Natural Park is one of the largest protected areas of Madagascar, with a surface of 3850 km 2. This park was entirely covered with rainforest vegetation before significant deforestation occurred along the east border, an inhabited area with many villages. Considering that the new species has an area of occupancy estimated to be less than 10 km 2, that is known to exist at only a single location, with a continuous decline of habitat due to deforestation, the conservation status as “Vulnerable” [VUD2] is proposed following the IUCN Red List Categories and Criteria ( IUCN 2012).

ETYMOLOGY. — The newly described species honors Paul Clément Harimalala, our guide from Maroantsetra and the Northeast area of Madagascar. Paul Clément was also the guide of Henri Laporte, who discovered and introduced into cultivation many species from Madagascar including Begonia harimalalae Scherber. & Duruiss. , sp. nov. in the nineties.

DESCRIPTION

Tuberous perennial lithophytic herb with short upright stems, 10-25 cm high.

Tuber

20-30 mm, irregular, rather flat, gnarled, strongly adherent on rock.

Stem

Fleshy herbaceous, glabrous, red with white tiny lenticels, 10- 20 mm long, 5 mm diam. Stipules persistent, membranous, green, translucent, nearly triangular, acuminate, the margin entire, 4 × 1 mm.

Leaves

3-8(-15), alternate, spreading, straight; petiole nearly as long as the blade, slightly canaliculate, 5-8 cm long, 2-4 mm diam., green tainted red, glabrous; blade sub-symmetrical, entire, thickly fleshy to succulent, ovate-lanceolate to sub-trullate, 10-15 cm long, 3-10 cm wide, base obtuse to rounded, apex long acuminate, glabrous; margin markedly dentate in upper two-third, teeth acuminate sometimes ending with a short mucro, adaxially bright green with a distinct dark red margin and sparse 1-2 mm small dark red spots between veins, semi-glossy, adaxially paler; venation pinnate, midrib and primary veins very prominent adaxially, concolorous, tainted red-brown; primary lateral veins 3-4 pairs, evenly spaced along midrib, remotely branching near margin, the first pair subopposite, the following ones usually alternate but sometimes sub-opposite; secondary venation indistinct.

Inflorescence

Axillary, dichasial, pauciflowered, bisexual, protandrous with basal male flowers and 1-2 distal female flowers; inflorescence axis 10-15 cm long, 3 mm diam., green, tainted red at base, glabrous; bracts present at anthesis, eventually caducous, elliptic, 3 × 5 mm, membranous, very light yellow green to red brown; bracteole absent; perianth segments white to pink.

Male flower. Perianth segments 4, free, pedicel 10-18 mm; outer perianth segments obovate, apex obtuse, 15 × 5-8 mm, markedly bicolorous, basally white, upper part and margins contrasting deep pink; inner perianth segments ellipticlanceolate to oblanceolate, 6 × 12 mm, white; stamens 12-18, yellow; androecium zygomorphic; filaments fused at the base into a column c. 1 mm long, free part c. 1 mm; anthers unilateral, longer than filaments, oblong, c. 2-3 mm, dehiscent through lateral longitudinal slits; connective not extended.

Female flower. Perianth segments 6, free; pedicel 12-15 mm; outer perianth segments obovate, apex obtuse, c. 6 × 12 mm, deep pink at apex, paler towards base; inner perianth segments obovate-oblanceolate, c. 5 × 11 mm, paler than outers, pale pink to white; ovary 3-winged, unequal, with one wing conspicuously larger than the two others, c. 8 mm long, green to red-brown, composed of 3 locules; placentae septal, bi-lamellate; ovules numerous; styles 3, fused at the base to about half length, bifid, pale yellow, persistent in fruit; stigma reniform, in a band, yellow.

Fruit

3-winged, dry capsule, nodding, the wings unequal.

Seeds

Unknown.

Figures

FIG. 4. — Begonia harimalalae Scherber. & Duruiss., sp. nov.: A, habit; B, leaf, adaxial side; C, male flower, front view; D, male flower, side view; E, androecium; F, female flower, face view; G, female flower, side view; H, gynoecium; I, styles and stigmas; J, gynoecium, early fruiting stage; K, ovary cross-section. Drawn from living plant, Scherberich 1153 (Drawing: Vanessa Damianthe). Scale bars: A, B, 1 cm; C, D, F-H, J, K, 2 mm; E, I, 1 mm.

FIG. 5. — Cet article est dédié à la mémoire de Jacky Duruisseau, qui nous a quittés peu de temps avant sa publication. Jacky était un passionné et spécialiste de Bégonia. Il possédait une collection exceptionnelle de spécimens originaires du monde entier, surtout d’Afrique et de Madagascar. Il a vécu plusieurs années au Gabon ainsi qu’à Madagascar, où il avait été professeur de mathématiques. Il y retournait régulièrement afin de retrouver les espèces peu connues de la Flore malgache mais aussi d‘explorer la péninsule de Masoala ou la forêt de la Makira, conscient de la rapide détérioration de la nature dans cette région. Il écrivait régulièrement des récits de ses voyages dans le Bégofil ou dans The Begonian.

FIG. 1. — Geographic distribution of Begonia ambanizanensis Scherber.& Duruiss.,sp.nov.,Begonia ambodiforahensis Scherber. & Duruiss.,sp.nov.and Begonia harimalalae Scherber. & Duruiss., sp. nov. in north-east Madagascar.