Dypsis humilis M.S.Trudgen, Rakotoarin. & W.J. Baker, Palms (1999+). 53(3): 140 (2009)

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Distribution

Map uses TDWG level 3 distributions (https://github.com/tdwg/wgsrpd)
Madagascar native (Palms (1999+). 53: 136 (2009))B
Northeast Madagascar, known from a single site above the Antainambalana River near the village of Ambodivoahangy west-northwest of Maroantsetra. (Rakotoarinivo, M., Trudgen, M.S. & Baker, W.J. 2009: The Palms of the Makira Protected Area, Madagascar. – Palms; Journal of the International Palm Society 53(3): 125-146)A

Habitat

  • Disturbed rain forest on granitic ridge top, 100-200 m. (Rakotoarinivo, M., Trudgen, M.S. & Baker, W.J. 2009: The Palms of the Makira Protected Area, Madagascar. – Palms; Journal of the International Palm Society 53(3): 125-146)A

Discussion

  • In reproductive morphology, this new species appears most similar to taxa in Dypsis Group 8 (e.g. D. concinna, D. corniculata, D. thiryana) of Dransfield and Beentje (1995) or perhaps Group 5 (D. procumbens). However, neither of these groups contains acaulescent species. In fact, only two other species of acaulescent Dypsis have been recorded from Madagascar. They were poorly known when The Palms of Madagascar (Dransfield & Beentje 1995) was published, but both have since been rediscovered (Dransfield et al. 2006). Neither can be confused with D. humilis. Dypsis acaulis (Group 18) from Masoala is a stemless or very short palm with bifid leaves that are chalky white on the undersurface, spicate inflorescences and staminate flowers with three antepetalous stamens. Dypsis aquatilis (Group 16), known from one locality in Manantenina in southeast Madagascar, is truly acaulescent and grows in water. It is more robust than D. humilis with very different leaf characteristics and has inflorescences branched to two orders. Dypsis humilis is thus a very distinct and easily. (Rakotoarinivo, M., Trudgen, M.S. & Baker, W.J. 2009: The Palms of the Makira Protected Area, Madagascar. – Palms; Journal of the International Palm Society 53(3): 125-146)A

Diagnosis

  • A D. acauli inflorescentia in 1 ordinem ramificanti et floribus staminatis 6 staminibus differt. Typus: Madagascar, Toamasina, Maroantsetra, Sahavalory forest near Ambodivoahangy, May 2007, Trudgen et al. 74 (holotypus K, isotypi TAN, MO, P). (Rakotoarinivo, M., Trudgen, M.S. & Baker, W.J. 2009: The Palms of the Makira Protected Area, Madagascar. – Palms; Journal of the International Palm Society 53(3): 125-146)A

Conservation

  • Critically endangered [CR (A1 + D)] (provisional assessment). Known only from one locality where fewer than ten individuals were observed. The site is outside the boundary of the Makira protected area and the forest is degraded. (Rakotoarinivo, M., Trudgen, M.S. & Baker, W.J. 2009: The Palms of the Makira Protected Area, Madagascar. – Palms; Journal of the International Palm Society 53(3): 125-146)A

Etymology

  • Not recorded. (Rakotoarinivo, M., Trudgen, M.S. & Baker, W.J. 2009: The Palms of the Makira Protected Area, Madagascar. – Palms; Journal of the International Palm Society 53(3): 125-146)A

Description

  • Clustering, acaulescent palm. Leaves 8 in the crown; petiole ca. 40 cm long, 3-4 mm wide, densely black/brown scaly, adaxially flat; leaf rachis ca. 40 cm long, in mid-leaf 1.2-2 mm wide, pubescent/scaly; leaflets sigmoid, 8 on each side of the rachis, borne regularly, inserted 1-5 cm apart, proximal leaflets 22-27 × 2-3 cm, with 2-3 folds, median leaflets 20-23 × ca. 2 cm, single fold, distal leaflets 10-14 × 2-3.5 cm, with 3-5 folds, abaxial surface sparsely brown scaly, distal margins of leaflets densely scaly, medifixed ramenta on abaxial surface of mid-veins in proximal half of leaflets, 0.1-0.4 mm long. Inflorescence 22-35cm long, interfoliar, branched to 1 order, erect; peduncle 10-15 cm long, 0.5-2 mm wide, pubescent; prophyll 6-7 cm long, 0.5-1 cm wide, 2-keeled, opening apically; Peduncular bracts 2; first peduncular bract similar to prophyll, 11-13 cm long, 0.5-1 cm wide, borne 4 cm above the insertion of the prophyll, opening apically; second peduncular bract triangular, not enclosing the peduncle, 0.2-0.4 cm long; rachis ca. 15 cm long, pubescent, with 4-6 rachillae; rachillae to 14 cm long, 0.8-1.4 mm diam., 0.5-1 cm apart; sparsely pubescent, triads 2-4 mm apart, arranged spirally. Staminate flowers 1.5 × 1.1mm, sepals 3, 0.7 mm long, petals 3, valvate, 1.5 × 0.9 mm, stamens 6, filament 0.5-0.7 × 0.2-0.3 mm, flattened, anthers 0.3 × 0.2 mm; pistillode 0.3 × 0.2 mm. Pistillate flowers 2.5 × 1.5 mm, sepals 3, petals 3, valvate, triangular, 2.1 × 1.3 mm, gynoecium gibbous, 1.3 × 1.2 mm, stigmas 3. Fruits immature, green, sickle shaped, 1.8 × 0.3 mm. Seeds immature, ca. 3 × 11 mm, endosperm homogeneous. (Rakotoarinivo, M., Trudgen, M.S. & Baker, W.J. 2009: The Palms of the Makira Protected Area, Madagascar. – Palms; Journal of the International Palm Society 53(3): 125-146)A

Materials Examined

  • Madagascar, Toamasina, Maroantsetra, Ambinanitelo: Sahavalory forest near Ambodivoahangy, May 2007, Trudgen et al. 74 (holotype K, isotypes TAN, MO, P), Trudgen et al. 75 (K, TAN). (Rakotoarinivo, M., Trudgen, M.S. & Baker, W.J. 2009: The Palms of the Makira Protected Area, Madagascar. – Palms; Journal of the International Palm Society 53(3): 125-146)A

Bibliography

    A. Rakotoarinivo, M., Trudgen, M.S. & Baker, W.J. 2009: The Palms of the Makira Protected Area, Madagascar. – Palms; Journal of the International Palm Society 53(3): 125-146
    B. Palms (1999+). 53: 136 (2009)