Begonia pteridoides Scherber. & Duruiss., 2017

Scherberich, David & Duruisseau, Jacky, 2017, Two new species of Begonia sect. Erminea (Begoniaceae) from Nosy Mangabe in Madagascar, Candollea 72 (2), pp. 257-263 : 261-263

Begonia pteridoides Scherber. & Duruiss. , spec. nova ( Fig. 2 , 3 A-D).

Typus: [ MADAGASCAR. Prov. Toamasina]: Plant in cultivation in Lyon Botanical Garden under n° 080405, originally collected by H. Laporte in 2001 in Nosy Mangabe , 21.IX.2016, Scherberich 1148 (holo-: LYJB!; iso-: G!, P!, TAN!) .

Begonia pteridoides Scherber. & Duruiss. is similar to B. bogneri Ziesenh. but differs by its highly divided leaves (vs entire linear leaf blades). Begonia pteridoides also differs from B. monicae Aymonin & Bosser , both having bipinnatifid leaves, by its less divided leaves and much longer lobes and the number of stamens (9-15 vs 25-30).

Tuberous perennial lithophytic herb with short clustered stems and spreading to pendulous leaves. Tuber small, 10- 20 mm, irregular, strongly adherent. Stem herbaceous, to 2 cm, red; internodes short 1-5 mm; Stipules persistent, the margins entire. Leaves 5-8, alternate, straight; petiole 4-12 mm long, 1-1.5 mm diam., hardly distinguishable from blade, cylindrical, slightly flattened on adaxial side, glabrous, red; blade 5-15 cm long, with twice-divided filiform segments 1-2 mm wide, segments 2-4 per side, arising at an angle of 40-50°, alternating every 0.2-2 cm, getting smaller toward apex, acute, the lower primary segments 2-6 cm long, light green and semiglossy adaxially, paler and glossy abaxially; midrib and primary lateral veins slightly raised adaxially. Inflorescence a monochasial cyme, axillary, bearing 3 flowers at summit, bisexual, protandrous, with basal male flowers and a solitary distal female flower; inflorescence axis 4.5- 8.5 cm long, 1-2 mm diam.; bracts present at anthesis, eventually caducous, lanceolate, 2.5-3 × 1.5-2.5 mm; bracteole absent; perianth segments pink. Male flower perianth segments 4, free, peduncle 9-17 mm; outer perianth segments sub-orbicular to elliptic-lanceolate, rounded at apex 5.2-6 × 8.7-9.5 mm; inner perianth segments obovate-oblanceolate 7.5-9.4 × 3.4-4.2 mm, paler; stamens 9-15; androecium zygomorphic; filaments fused at the base into a column 0.8-1 mm long, free part 0.5-1 mm; anthers longer than filament, oblong, 1.5 mm, dehiscent through lateral longitudinal slits; connective not extended. Female flower perianth segments 6(-7), free; peduncle 10-12 mm; outer perianth segments obovate, apex obtuse, 6.5-8 × 4.2-5 mm; inner perianth segments oblanceolate, 7-8 × 3.2-4 mm; ovary 3-winged, unequal, with one wing conspicuously larger than the two others, 5-7 mm long versus 2-2.5 mm long, green to red-brown, composed of 3 locules, placentae septal, bi-lamellate; ovules numerous, white; styles 3(-4), fused 1/3 to halfway, pale yellow, persistent in fruit; stigma reniform, in a band, yellow; Fruit a 3-winged dry capsule, nodding, the wings unequal. Seeds unknown.

Distribution and ecology. – Known only from the type collection in Nosy Mangabe, Madagascar, growing on mossy granite boulders. Flowering in cultivation has been observed from September to June.

Conservation status. – The locus classicus has never been relocated since the original collection and as H. Laporte died shortly after his return from Madagascar, the information regarding the collection locality was given by his guide Paul Clément Harimalala. As B. pteridoides is restricted to Nosy Mangabe and as such has a very restricted area of occupancy which is typically <20 km 2, the conservation status as “Vulnerable” [VU D2] is proposed following the IUCN Red List Categories and Criteria ( IUCN, 2012).

Notes. – Begonia pteridoides was collected by H. Laporte on his last trip to Madagascar, just before he died of a severe form of malaria. It has never been recollected since and unfortunately no herbarium specimens have been sourced. Over the years, living plants have been shared with Begonia collectors and although it is a very tricky plant to keep alive, it is still present in a few specialized collections and among terrarium growers. The habit is erect in cultivation but a picture taken in situ by H. Laporte, shows a colony of plants growing on granite, with pendent leaves. That habit could reflect a reaction to a momentarily dry period.

Figures

Fig. 2. – Begonia pteridoides Scherber. & Duruiss. 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. Styles and stigmas; I. Ovary; J. Ovary cross-section. [Scherberich 1148, LYJB] [Drawing: Vanessa Damianthe]

Fig. 3. – Begonia pteridoides Scherber. & Duruiss. (A-D) and Begonia nosymangabensis Scherber. & Duruiss. (E-F). A. Habit in cultivation; B. Stem; C. Leaf, abaxial side; D. Young plant showing juvenile leaves; E. Habit in cultivation; F. Stem. [Photos: A-D, F: David Scherberich; E: Evelyne Bouquet]