Saturday, July 1, 2017

[Botany • 2017] Vietnamocasia dauae • A New Genus from Central Vietnam belonging to the Alocasia-Colocasia clade (Araceae)

Vietnamocasia N.S. Lý, S.Y. Wong & P.C. Boyce
Vietnamocasia dauae N.S. Lý, T. Haevermans, Y.S. Wong & D.V. Nguyen


Vietnamocasia, a new monotypic aroid genus in the Alocasia-Colocasia clade, is described with the type species, Vietnamocasia dauaeVietnamocasia is distinguished by possessing free individual staminate flowers, lacking expanded synconnectives, and having nodding inflorescences. Vegetatively Vietnamocasia is reminiscent of species of the distantly closely related Alocasia Cuprea Group, although Vietnamocasia is so far only known from the type locality in Central Vietnam, over 1200 km NE from the nearest representative of the Alocasia Cuprea Group. The phylogenetic analyses of Vietnamocasia dauae together with representative taxa from all genera of the Alocasia-Colocasia clade recovered Vietnamocasia as a strongly supported clade sister to Alocasia, together nested in a clade to which Leucocasia is a sister taxon. Vietnamocasia dauae is illustrated from living plants and with a line drawing. A key to all genera of Alocasia-Colocasia clade is included.

Keywords: Endemics, Indochina, Malesia, phylogeny, Vietnamocasia dauae, Monocots

Figure 3. Vietnamocasia dauae. A. Habit; B. Leaf blades: adaxially and abaxially with their closed-up of the leaf bases (from left); C. Inflorescence (front view); D. Cataphyll, spathe (back view), and spadix (from left); E. Close-up of pistillate (E1), sterile interstice (E2) and staminate zones showing free individual staminate flowers (a red arrow, E3); F. Closed-up of appendix; G. pistillate zone after anthesis with lower spathe; H. Fruit spathe (back and front views); I. Longitudinal section of fruit spathe and infructescences (from left).

Vietnamocasia N.S.Lý, S.Y.Wong & P.C.Boyce, gen. nov. 
Type: Vietnamocasia dauae N.S.Lý, S. Y. Wong, T.Haevermans & D.V.Nguyen, sp. nov.

 Etymology:— Vietnamocasia is compounded from the Greek classical name kolokasia, itself from an old Middle Eastern name qolqas (Nicolson 1987) and the root of Alocasia and Leucocasia (and the more distantly related Colocasia) + Vietnam. 

Distribution:— Vietnamocasia is so far known only from the type locality and its vicinity. 

Ecology:— At Mount Dầu Vietnamocasia dauae grows in moist shady understory of hillsides in secondary broadleaved forest dominated by dipterocarps at 150–490 m elevation. At the other known locality, Cà Đam, it occurs in primary evergreen broad-leaf forest at about 790 m elevation.

Vietnamocasia dauae N. S. Lý, T. Haevermans, Y. S. Wong & D. V. Nguyen, sp. nov. 

Etymology:— The specific epithet is for Mount Dầu, the type locality, treated as feminine.  

Lý Ngọc-Sâm, Wong Sin Yeng, Thomas Haevermans, Nguyễn Văn Dư and PETER C. Boyce. 2017. Vietnamocasia, A New Genus from Central Vietnam belonging to the Alocasia-Colocasia clade (Araceae). Phytotaxa. 303(3);  253–263.  DOI: 10.11646/phytotaxa.303.3.5

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