Discovery of a rare genus Litostigma (Gesneriaceae) from northern Vietnam with the supplementary description of L. crystallinum

摘要: The Sino-Vietnamese limestone karsts show specially high levels of plant diversity among Indo-China floras,and also are biodiversity hotspots in the world,and many new species or genera of Gesneriaceae have been found there recently. The genus Litostigma Y.G. Wei, F. Wen & M. Möller (Gesneriaceae) was reported firstly from limestone areas of southwestern China in 2010, included two species, namely Litostigma coriaceifolium Y.G. Wei, F. Wen & M. Möller (Typus generis) from southwestern Guizhou, and Litostigma crystallinum Y.M. Shui & W.H. Chen from southeastern Yunnan. We fortunately found Litostigma crystallinum from Ha Giang, northern Vietnam, and reported here to sufficiently know the diversity of Gesneriaceae in Vietnam. The description of Litostigma crystallinum was supplemented base on the collections from Ha Giang, northern Vietnam, and the habitat photos were also provided. The discovery of Litostigma crystallinum from northern Vietnam demonstrates the closely floristic relationship between northern Vietnam and southern China once again. The new localities are also very important for the conservation of Litostigma crystallinum.