Phylogenomics reveal Populus gonggaensis as a hybrid between P. lasiocarpa and P. cathayana (Salicaceae)

High levels of intra-specific polymorphism and frequent hybridisation make it difficult to define species and correctly apply their scientific names. Populus L. is a challenging genus with plentiful natural and artificial hybrids. This study is a part of the project ‘Flora of Pan-Himalaya’ and aims to determine the taxonomic identity of P. gonggaensis N. Chao & J.R. He and to find out whether it is of hybrid origin. Whole-genome sequencing data were obtained from 57 samples. The SNP matrix was developed for phylogenetic reconstruction, ABBA-BABA statistics, PCA and ADMIXTURE analysis. The results indicate that P. gonggaensis is a spontaneous hybrid between P. lasiocarpa and P. cathayana . This study points out the importance of SNP data and comprehensive analyses for discovering the potential interspecific hybridisation and clarifies the usage of the name. In addition, the lectotype of P. gonggaensis was designated.