The Phylogeny Of Hedychium (Zingiberaceae) And The Evolutionary Relationship Between The Two Varieties Of Hedychium Villosum

With more than 50 species, Hedychium J Koenig is the only genus of ginger family ranging low areas to high-altitude regions of tropical areas, which centered at Himalayan regions. The taxonomic position of species within Hedychium genus has been highly disputed.This study aims to construct the molecular phylogeny of Hedychium to infer its morphological characters evolution, divergent time of the main clades and historical biogeography based on ITS, matK and the combined DNA sequences, which have not been examined in this genus before. Maximum parsimony, Bayesian analysis were performed to reconstruct the phylogenetic trees of the genus. The monophyly of Hedychium is highly supported, within which four distinct clades (Ⅰ,Ⅱ,ⅢandⅣ) were distinguished: plants in cladeⅠand cladeⅢhave high altitude, they always distribute in Himalaya regions, there is only one flower per bract and the bracts imbricate; There are the most species in cladeⅡ, they distribute widely but in low-altitude regions, there are more than one flower per bract; the clade IV plants are all epiphytic, and most of them just distribute in Southeast Asia, there is one or more flowers per bract.Based on the data from Beast analysis, we infer that it has closed relationship between the Himalayas lift and the Hedychium divergence, especially twice global drought, and the genus Hedychium possibly originated in Southeast Asia. After mapping the morphological characters on the phylogenetic trees of Hedychium, we infer that evolution trend of the genus is from epiphytic to terrestrial, there is one flower per bract in high-altitude plants and more than two flowers per bract in low-altitude plants.In this paper, we study on the evolutionary relationship between two varieties of Hedychium villosum (Zingiberaceae), and the two varieties of Hedychium villosum, var. villosum and var. tenuiflorum, are only morphologically and taxonomically different in plant and flower size. Our results of chromosome number counting released that var. tenuiflrum is diploidy and var. villosum is tetraploidy. The morphology of two varieties are characterized by autopolyploidy, and the isozyme analysis of two varieties also confirmed that var. tenuiflrum is diploidy and var. villosum is autotetraploidy. Although flowers of two varieties do not have any difference in floral shape, two varieties can be easily distinguished morphologically because the plants, leaves and flowers of autotetraploid var. villosum are consistently larger than diploid var. tenuiflorum. Two varieties possess distinct geographic range and habitats, and no sympatric distribution was found. Autotetraploid var. villosum has a broader geographic distribution range and more diverse ecological habitats than diploid var. tenuiflorum. Two varieties are completely reproductively isolated because the flowering time of two varieties did not overlap at all. Two varieties fulfill the requirements of multiple species concepts, and should be named as two distinct species. H. villosum provide an excellent example of autopolyploid speciation in ginger family. Followed the basic naming method for diploid/autotetraploid pairs, autotetraploid var. villosum should be keep as Hedychium villosum and diploid var. tenuiflorum could be named as Hedychium diplovillosum Fei Yu, W. John Kress & Jiangyun Gao.