Dracaena rosulata Mwachala & Eb.Fischer, 2013

Mwachala, Geoffrey & Fischer, Eberhard, 2013, Dracaena rosulata (Asparagaceae) - a new species from D. R. Congo, Phytotaxa 88 (1), pp. 6-8 : 6-8

Dracaena rosulata Mwachala & Eb.Fischer sp. nov. ( Fig. 1 )

Dracaena phrynoidi et D. phanerophlebia habitu rosulato similis sed petiolis brevissimis vel nonnullis et inflorescentias elongatis paniculatis valde differt. Dracaena braunii inflorescentia similis sed habitu caulibus elongatis et floribus basim breviter connatis differt.

Type: — D. R. CONGO: Bas Congo ( III) , Kisantu, Zongo, 13 July 1953, H. Callens 4158 (holotype BR!).

Perennial rosulate herb. Rhizome creeping, up to 12 cm long and 0.5 cm in diameter, covered in the upper part by brownish hypophylls up to 0.28–0.30 × 0.14–0.15 cm. Leaves in a dense basal rosette, petiole very short or lacking, if present broadly winged and not exceeding 1 cm in length, lamina broadly elliptic, widest at middle, acuminate at apex, herbaceous, 12–14 × 4.5–7 cm, parallel main veins and secondary anastomosing veins obscure on upper surface and conspicuous on lower surface. Inflorescence 19–25 cm long, erect, arising from the centre of the rosette, basal leaves on peduncle 1.5–2 × 0.5 cm, sterile bracts 2–3 along middle of peduncle, upper part of inflorescence paniculate, with up to 19 glomerules of flowers (lateral partial inflorescences), each glomerule composed of 5–8 flowers. Bracts of glomerules minute, 0.1 × 0.1 cm, pedicel 0.18–0.2 cm long. Flowers with white perianth, 1.4–1.6 cm long, fused over basal 0.2–0.3 cm, lobes 6, narrow, linear, 1.2–1.4 × 0.1 cm. Stamens 6, 1.1–1.2 cm long, anthers 0.2 × 0.1 cm. Ovary ovoid, 0.2 × 0.15 cm. Fruit not known.

Habitat: —The herbarium label states “sousbois”. Thus, the species probably grows in the understorey of lowland rainforest.

Distribution: —This species is only known from the type collection made in 1953. The locality Zongo is situated in the phytogeographical unit Bas-Congo near Mbanza Ngungu at S 04°47’ E 14°54’ ( Bamps 1982). This area is just south of the Lower Guinea Centre of endemism ( Linder 2001). The vegetation is described as a mosaic of Guineo-Congolian rainforests and secondary savanna ( White 1983). The discovery of this species demonstrates the need of further field research.

Conservation Status: — Data deficient ( DD). We do not know enough about the natural populations to be able to assess the conservation status of this species. However, the species is only known from a single herbarium gathering dated sixty years ago. As the type locality is situated between the two cities of Matadi and Kinshasa there is probably a high pressure due to the growing population .

Dracaena rosulata shows a unique combination of character-states within Dracaena s.str. The rosulate habit resembles that of Dracaena phyrnoides Hooker (1862 : t. 5352) and Dracaena phanerophlebia Baker (1898: 448) . It differs, however, in the sessile leaves which almost lack the distinct long petiole of D. phyrnoides and D. phanerophlebia , and the paniculate elongated inflorescence that is capitate in the two latter species. The inflorescence of Dracaena rosulata resembles that of D. braunii Engler in Baker & Engler (1892: 479), but the latter species differs distinctly in the elongate stem with the leaves spaced on sterile shoots and almost also lacking a petiole. The flowers of Dracaena braunii are about 2.3 cm long and the fused basal part is 1 cm long, while in Dracaena rosulata it does not exceed 0.3 cm. The rosulate habit recalls that of some Sansevieria species but they are all succulent plants while our species has firm but herbaceous leaves.

Figures

FIGURE 1. Dracaena rosulata—A, B, habit; C, detail of lower leaf surface showing veins; D, detail of inflorescence with postfloral flower; E, F, flowers. All drawn from the holotype by E. Fischer.