Study of genetic relationships and phylogeny of the native Populus in Southwest China based on nucleotide sequences of chloroplast trnT-trnF and nuclear DNA

摘要

Unique historical factors and ecological conditions make Southwest China a natural distribution and variation center for trees of the genus Populus in China. However, little is currently known about the native poplars occurring in this region, and considerable doubt still exists regarding the classification and evolutionary relationships of poplar species. In this study, nuclear and chloroplast DNA (cpDNA) sequences were utilized to determine the genetic relationships and phylogeny of Populus species in Southwest China. The results suggest that P. pseudoglauca belongs to the section of Tacamahaca. Further, P. schneideri may be a natural hybrid of P. kangdingensis and P. cathayana and, thus, it should likely not be regarded as a variety of P. kangdingensis, as in the existing classification system. In addition, cluster analyses showed that P. gonggaensis may be derived from a cross between species of section Leucoides and P. cathayana or P. schneideri of section Tacamahaca, although it is still doubtful whether P. gonggaensis can be regarded as a separate species, due to its narrow distribution range. The parents of the Luding poplar may be P. yunnanensis and P. lancifolia. P. butuoensis showed a close affinity to species of section Leucoides and had a close relationship with P. gonggaensis or P. lasiocarpa. However, further research is needed in order to appropriately classify these as species or varieties. The incongruence between phylogenetic trees based on nuclear- and chloroplast-DNA sequence data may be due to the different inheritance patterns between nuclear- and cpDNA genome.