Một loài mới thuộc chi Eustigma (họ Hamamelidaceae) tìm thấy ở Khu BTTN Hòn Bà, Việt NamA new species of Hamamelidaceae, Eustigma honbaense H.Toyama, Tagane & V.S.Dang, sp. nov., is described from Hon Ba Nature Reserve, Vietnam. This species is similar to Eustigma oblongifolium Gardner & Champ., but differs from it in having entire leaves, longer infructescences, capsules with a longer apical part and seeds with a larger hilum. A description, preliminary conservation assessment, illustration and photographs of the new species are provided, as well as an updated key to the genus Eustigma.
Keywords: DNA barcoding, flora, Indochina, matK, rbcL, taxonomy
Eustigma Gardner & Champ. (Gardner 1849) is a small genus of the Hamamelidaceae, distinguished from other genera by small auriculate petals and the greatly enlarged stigma (Harms 1930; Zhang et al. 2003). Currently, three species are known in the genus: E. balansae Oliv., E. lenticellatum C.Y.Wu and E. oblongifolium Gardner & Champ., distributed in mainland China, Laos, Taiwan and Vietnam, among which E. balansae is the only species recorded in Vietnam (Tardieu 1965; Hsieh 1993; Hô 2003; Zhang et al. 2003; Newman et al. 2007).
From 2013 to 2014, as part of a collaborative programme to document the biodiversity and ecology of Southeast Asia, Kyushu University (FU) together with Institute of Tropical Biology, Vietnam (VNM) carried out botanical field surveys in Hon Ba Nature Reserve, in South Vietnam (Figure 1) and found a species of Eustigma that was distinct from any of the three known species. Here, we describe this plant as a new species, Eustigma honbaense H.Toyama, Tagane & V.S.Dang, and place the species within the wider generic context by providing an updated identification key to all known species of Eustigma. Our conclusion is based on observations of specimens in the herbaria, BKF, E, HN, K, KAG, KYO, L, P, TI, and VNM, and specimen images on the website of JSTOR Global Plants (https://plants.jstor.org/). We also provide DNA sequences of two DNA barcode regions; the partial genes for the large subunit ribulose-1,5-bisphosphate carboxylase oxygenase (rbcL) and maturase K (matK) (CBOL Plant Working Group 2009); established protocols were used to determine the sequences of these regions (Kress et al. 2009; Dunning and Savolainen 2010).
Eustigma honbaense H.Toyama, Tagane & V.S.Dang, sp. nov.
VIETNAM. Khanh Hoa Province, Hon Ba Nature Reserve, evergreen forest margin along streamside, 401 m alt., 12°06.57'N, 108°59.21'E (DDM), 14 July 2014, S. Tagane, H. Kanemitsu, V.S. Dang, H. Tran, X.N. Loi, N.D. Thach, N. Dinh & H.N.P. Hieu V1586 (holotype: KYO!; isotypes: FU!, VNM!, the herbarium of Hon Ba Nature Reserve!).
Figure 3. Terminal and axillary bud of Eustigma honbaense H.Toyama, Tagane & V.S.Dang, sp. nov.
Eustigma honbaense is named after the type locality, Hon Ba Nature Reserve.
(PhytoKeys 65: 47-55 (15 Jun 2016))
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