Amorphophallus dumboi Eb.Fisch., B.Dumbo & L.Dumbo, 2022

Fischer, Eberhard, Dumbo, Bonny & Dumbo, Landry, 2022, A new species of Amorphophallus (Araceae) from Eastern D. R. Congo, and a new record of the genus from Rwanda, Plant Ecology and Evolution 155 (3), pp. 333-342 : 333

Amorphophallus dumboi Eb.Fisch., B.Dumbo & L.Dumbo sp. nov.

Figs 1 , 2 , 5A

Type.

D.R. CONGO - Lacs Edouard et Kivu • S Kivu, Kahuzi-Biéga National Park, transitional rainforest at Mulolo , partially submerged along small stream; 2°29 ’06.42” S, 28°21 ’22.09” E; 1108 m; Dec. 2018; B. Dumbo & L. Dumbo s.n.; holotype: BR [BR0000015253569V] .

Diagnosis.

Amorphophallus dumboi differs from A. margretae in the leaves and inflorescences that appear at the same time on the same tuber (leaves appear after inflorescence in A. margretae ), the peduncle about 4 times the length of the spathe (peduncle not exceeding 2 times the length of the spathe in A. margretae ), and the inner base of spathe with irregular rounded to elongate smallpox-like projections of 0.2-1 mm in length, between and on the veins (inner base of spathe smooth, with shallowly elevated dark veins in A. margretae ).

Description.

Tuber irregular-globose to ovoid, 6-8 × 2.5-5.5 cm. Leaf with 3 pinnae, each 1-pinnate to 1-pinnatifid. Petiole 70-75 cm long. Lamina diameter up to 120 cm. Rachis of each pinna 35-37 (48) cm long, winged. Terminal leaflet up to 16.5 cm long and 4.5 cm wide, with long acumen of 2.5 cm length. Cataphylls 3, the inner one ca 9-10 × 1.5-2 cm, the outer ones much shorter, dark with darker veins. Inflorescence up to 125 cm tall, erect, appearing simultaneously on the same bulb with the leaf, smell very unpleasant. Peduncle smooth, 90-98(-105) cm × 1.5 cm, with small roundish spots. Spathe 18-25.5 (30) cm long, cylindrical, without a constriction, tube 11-12(-15) × 5.8-6.2 cm, interior (adaxial) side basally with irregular rounded to elongate smallpox-like projections of 0.2-1 mm length, between and on the veins, open limb erect, rim-shaped to elongate-triangular 15-16 × 6-8 cm, purple, margin entire. Spadix sessile, 25.5-32.5(-38) cm long, slightly longer than spathe, carpellate zone cylindrical, 2.5-5.2 × 2.5-2.8 cm, flowers mostly congested, staminate zone cylindrical, 4.8-5.3 × 2.5-2.8, flowers dense, appendix conical, 16-18 × 3.8-5 cm, smooth and velvet-like, basally with longitudinal furrows, staminodes absent, without a sterile zone between the carpellate and staminate zone. Carpellate flowers 4-4.6 mm long, ovaries elongate-ovoid, 3.5-4 × 3-4 mm, unilocular, style slender, 1-1.2 mm long, same colour as ovary, stigma 1.2-1.3 mm in diameter, usually unlobed and head-shaped. Staminate flowers 1-1.5 × 1.3-2.24 mm, with 3-4 stamens; anthers free, globose to cubic with rounded edges, filaments only 0.1-0.3 mm long, free or sometimes basally connate but not forming a columna, pores circular, one apical pore per theca. Infructescence unknown.

Distribution.

Only known from the rainforests in the southern part of Kahuzi-Biéga National Park, Eastern Democratic Republic of the Congo (Fig. 5A ).

Habitat.

Transitional montane rainforest at Mulolo, partially submerged along small stream, 1108 m, together with numerous ferns and Impatiens species.

Phenology.

Observed in flower from August to April.

Etymology.

Named after Dumbo Kilundo (1 January 1930-18 September 2020), one of the most knowledgeable botanists from D.R. Congo, despite that he never received formal training. Born in Kisanga (Mulolo), Shabunda, he went to the Institut de Recherche Scientifique en Afrique Centrale (IRSAC) at Lwiro, today Centre de Recherche en Sciences Naturelles (CRSN). There he worked first with A.R. Christiaensen and later with G. Troupin. He made major contributions to the knowledge of the Flora of Central Africa, first for the IRSAC, later as Head of Irangi Forest Reserve and for the Herbarium of Lwiro.

Preliminary IUCN conservation assessment.

Critically Endangered: CR B2ab(iii). Amorphophallus dumboi is only known from the type locality. The estimated AOO is 4 km² (assuming a 4 km² grid cell size). The habitat, a submontane rainforest, is under potential threat of illegal logging but is actually protected as part of Kahuzi-Biéga National Park.

Figures

Figure 1. Amorphophallus dumboi. A - B, D. Habit with inflorescences showing the third author for comparison. C. Leaf, showing the third author for comparison. E. Base of plant showing roots and upper part of tuber. F. Leaf. G. Inflorescence. Scale bars: 20 cm (A-D), 1 cm (E), 5 cm (F-G). Photographs taken at the type locality on 10 Dec. 2018 by Bonny Dumbo.

Figure 2. Amorphophallus dumboi. A. Inflorescence. B - C. Detail of spadix showing staminate (above) and carpellate zone (below). D. Carpellate flowers. E - G. Ornamentation on inner side of spathe. Scale bars: 5 cm (A), 5 mm (B-C), 1 mm (D-G). Photographs taken at the type locality on 10 Dec. 2018 by Bonny Dumbo (A), and in the laboratory by Eberhard Fischer (B-G).

Figure 5. A. Distribution map of Amorphophallus dumboi, A. margretae, and A. mayoi in D. R. Congo and Rwanda. B. Distribution map of A. mayoi.