J Syst Evol ›› 2023, Vol. 61 ›› Issue (1): 22-41.DOI: 10.1111/jse.12902

• Research Articles • Previous Articles     Next Articles

Species delimitation of the liquorice tribe (Leguminosae: Glycyrrhizeae) based on phylogenomic and machine learning analyses

Lei Duan1*, Li‐Na Han2, Bin‐Bin Liu3, Artem Leostrin4, AJ Harris1, Lin Wang5, Emine Arslan6, Kuddisi Ertuğrul6, Mikhail Knyazev7, Elena Hantemirova7, Jun Wen8*, and Hong‐Feng Chen1*   

  1. 1 Guangdong Provincial Key Laboratory of Applied Botany, South China Botanical Garden, Chinese Academy of Sciences, Guangzhou 510650, China
    2 College of Forestry and Landscape Architecture, South China Agricultural University, Guangzhou 510642, China
    3 State Key Laboratory of Systematic and Evolutionary Botany, Institute of Botany, Chinese Academy of Sciences, Beijing 100093, China
    4 Komarov Botanical Institute, Russian Academy of Sciences, Professor Popov Street 2, Saint Petersburg 197376, Russia
    5 Guangdong Eco‐Engineering Polytechnic, Guangzhou 510520, China
    6 Department of Biology, Faculty of Science, Selçuk University, Konya 42031, Turkey
    7 Institute of Plant and Animal Ecology, Ural Branch, Russian Academy of Sciences, Yekaterinburg 620144, Russia
    8 Department of Botany, National Museum of Natural History, MRC 166, Smithsonian Institution, Washington, DC 20013‐7012, USA

    *Authors for correspondence. Lei Duan. E‐mail: duanlei@scbg.ac.cn; Jun Wen. E‐mail: wenj@si.edu; Hong‐Feng Chen. E‐mail: h.f.chen@scbg.ac.cn
  • Received:2022-01-22 Accepted:2022-07-10 Online:2022-07-25 Published:2023-01-01


The liquorice tribe Glycyrrhizeae is a leguminous herbaceous group of plants comprised of the genera Glycyrrhiza and Glycyrrhizopsis. Some Glycyrrhiza taxa contain glycyrrhizin, a pharmacologically significant sweet substance that also has applications in crafting industrial materials. Here, we utilized an expanded taxon sampling of Glycyrrhizeae to reconstruct the phylogenetic relationships in the tribe based on genome skimming data, including whole chloroplast genomes, nuclear ribosomal DNA, and low-copy nuclear DNA. We also launched machine learning analysis (MLA) for one species pair with controversial taxonomic boundary. The integrated results indicated Glycyrrhizopsis should be split from Glycyrrhiza, while the former genus Meristotropis should be treated as part of Glycyrrhiza. Glycyrrhizopsis includes two species, Glycyrrhizopsis asymmetrica and Glycyrrhizopsis flavescens, and we recognize 13 species in Glycyrrhiza: Glycyrrhiza acanthocarpa, Glycyrrhiza astragalina, Glycyrrhiza bucharica, Glycyrrhiza echinata, Glycyrrhiza foetida, Glycyrrhiza glabra, Glycyrrhiza gontscharovii, Glycyrrhiza lepidota, Glycyrrhiza macedonica, Glycyrrhiza pallidiflora, Glycyrrhiza squamulosa, Glycyrrhiza triphylla, and Glycyrrhiza yunnanensis. We propose a broader G. glabra that includes former Glycyrrhiza aspera, G. glabra s.s., Glycyrrhiza inflata, and Glycyrrhiza uralensis, and represents the glycyrrhizin-contained medicinal group. Our ancestral state inferences show the ancestor of Glycyrrhiza lacked glycyrrhizin, and the presence of glycyrrhizin evolved twice within Glycyrrhiza during the last one million years. Our integrative phylogenomics-MLA study not only provides new insights into long-standing taxonomic controversies of Glycyrrhizeae, but also represents a useful approach for future taxonomic studies on other plant taxa.

Key words: character evolution, Glycyrrhiza, machine learning analysis, medicinal group, phylogenomics, species delimitation