Abstract
The taxonomy of Quercus langbianensis and its relatives in Vietnam and Cambodia have been revised based on evidence obtained from field observations, morphological comparison of herbarium specimens and molecular analyses using both classic and next generation DNA markers. Based on Bayesian inference using rbcL, matK and ITS regions and Neighbour-joining tree using genome-wide sequences amplified with multiplexed inter-simple sequence repeat (ISSR) primers (MIG-seq), the authors recognised ten species in the complex in Vietnam and Cambodia, three of which are newly described in this paper: Q. baolamensis sp. nov., Q. bidoupensis sp. nov. and Q. honbaensis sp. nov. These new species are all phenotypically similar to Q. langbianensis s. str. in having lanceolate to oblanceolate leaf shape, upper 4–5/6–serrated leaf margin, acute or acuminate leaf apex and bracts of cupule arranged in 5–9 rings but distinguished both morphologically and phylogenetically. In molecular phylogenetic reconstructions, Q. bidoupensis is not close to any other species. In the Bayesian tree, Q. honbaensis is sister to both Q. blaoensis and Q. camusiae that are found in the same locality but morphologically distinct and those three species are sister to Q. langbianensis s. str., while Quercus baolamensis is not sister to Q. langbianensis s. str. in both the Bayesian tree and MIG-seq tree. In addition, Q. cambodiensis and Q. baniensis previously reduced to Q. langbianensis s. lat. have been recognised as distinct species. Six species were in need of lectotypification and that is undertaken herein.
Highlights
The genus Quercus L., with 400–500 species, is the largest genus in the family Fagaceae (Nixon 1993, Valencia-A et al 2016)
Observation in the field In Hon Ba Nature Reverse, tree diversity was examined in eight plots of 100 m × 5 m and four species of Quercus (Table 1) were found including Q. poilanei and three species of the Q. langbianensis complex: Q. blaoensis, Q. camusiae and an undescribed species, Q. honbaensis
Quercus camusiae was distinct from Q. honbaensis and Q. blaoensis in that shoots and leaves were golden tomentose when young
Summary
The genus Quercus L., with 400–500 species, is the largest genus in the family Fagaceae (Nixon 1993, Valencia-A et al 2016). One of them is Quercus langbianensis Hickel & A.Camus (1921), described from Mt. Langbian of Lam Dong Province, southern Vietnam. The authors’ recent comparison based on the collections of Q. camusiae and Q. cambodiensis from their type localities revealed that both Q. camusiae and Q. cambodiensis are distinct species from Q. langbianensis s. Hereafter designated as “Q. langbianensis complex” and its similar species such as Q. auricoma A.Camus in which Q. cambodiensis was recently included (Tagane et al 2017). Deng et al (2010) studied the relationship of Q. camusiae, Q. cambodiensis and Q. langbianensis and concluded that the three species are phenotypically indistinguishable. Their study was based on the comparison of a limited number of herbarium specimens
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