Lasianthus includes at least 180 species, among which more than 160 are distributed in tropical Asia, ca. 20 in Africa, one in Australia, and three in tropical America (Zhu 2002). This genus is taxonomically difficult because the morphological characters of the leaves, stipules and bracts are very variable, while the flowers and fruits are relatively small and most of the time missing from herbarium specimens, therefore leaving only a few diagnostic characters available for delineating the species (Zhu et al. 2012).
In recent years, taxonomic revisions of Lasianthus have been published for Thailand (Zhu 2001), China (Zhu 2002) and Malesia (Zhu et al. 2012), whereas the Vietnamese taxa remain poorly studied. At present, there are 31 species of Lasianthus recognized for Vietnam (Phạm 2000).
Between 2012 and 2014, we carried out numerous field surveys to assess the plant diversity at the Hon Ba Nature Reserve, southern
Vietnam. During one of our trips, we discovered a species of Lasianthus that was distinct from all the known congenerics reported to occur in Vietnam. We were also unable to find a match for this unidentified taxon in the Vietnamese Herbaria (HN and VNM) and The Forest Herbarium, Bangkok (BKF).
Lasianthus yaharae V.S. Dang, Tagae & H. Tran
Lasianthus yaharae V S. Dang, Tagane & H. Tran
Type. Vietnam. Khanh Hoa Province, Hon Ba Nature Reserve, near peak, montane evergreen forest dominated by Fagaceae, alt. 1521 m a.s.l., 12°07'06"N, 108°56'51"E, 18 July 2014 Tagane S., Kanemitsu H., Son V.D., Tran H. with Loi X.N., Thach N.D., Dinh N. & Hieu P.N.H. V1741 (holo- type VNM; isotypes FU!, KYO!, Station of Hon Ba Nature Reserve!, VNM!). — Paratype: Vietnam. Klianli Hoa Province, Hon Ba Nature Reserve, 30 km west of Nha Trang City, alt. 1521 m a.s.l., 12°07W'N, 108°56'51"E, 2 November 2012 Son V.D., Tagane S., Toyama H., Fuse K.. Naganiasu H„ Hop T, Lam T.T. & Yaliara T. VHB44 (VNM!).
Distribution and habitat.
Hon Ba Nature Reserve, Khanh Hoa Province, southern Vietnam. In moist evergreen forest, dominated by members of Fagaceae, at ca. 1500111 a.s.l.