Genetic Diversity And Phylogeography Of Liriodendron Chinense

Liriodendron Chinense is an endangered deciduous perennial xylophyta, one of the genera with a East Asia-North American disjunctio. It has important scientific value for study on paleobotany, genealogy and geobotany. As a, relic species from the tertiary, mainly occurs in subtropical China. It has high economic and ecological value. In this research, the genetic diversity and phylogeography of L.Chinense were studied.The main results as follows:1. Morphological diversities among populations were discussed on the basis of traits such as the leaf, the seed, the aggregate fruit, the floral organs, the pollen. The above traits were significantly difference among populations. The mean germinations of most seed sources studied were at 3% to 5%. Leaf shape and floral organ size had significantly geographic variation along the longitude. Side sinus depth and top sinus depth in eastern region were deeper than in western region. Eastern flower was smaller than western's. The net photosynthetic rate of the highest provenance was 2.36 times the lowest.2. Pollen had significant polymorphism among populations. Pollen morphology and ultrastructure were significant geographic variations. Pollen type of western region was more primitive relatively than eastern region. L. Chinense pollen was a more evolutionary type in the Magnoliaceae.3. In this study,20 SSR primers were used to reveal the genetic diversity of 22 populations, low genetic diversity (Nei(h)=0.5577)was found. Genetic diversity has higher geographic differentiation between eastern and western (Fst=0.3018). It maybe caused by significant genetic drift which was due to geographical isolation, little gene flow and small population scale. Each population exited significant linkage disequilibria, implied that the stochastic causes such as genetic drift might be the main reason of linkage disequilibria.4. Significant geographic structure of haplotype was detected. Populations of western and eastern ranges had own unique haplotypes, which implied that eastern and western range had different origins. Two contrasting glacial refugia were found in eastern and western distribution regions. Yunnan-Guizhou plateau and southern Sichuan maybe provided refugium for western region; Southren Wuyi-mountain maybe served the other one for eastern region. After ice age, we speculated that L.Chinenese in eastern and western refugia maybe spreaded in different directions to the north. Populations survived in eastern and western refugia migrated and then mixed in border zone intersection of Chongqing, Guizhou, Hunan and Hubei, resulting in that the region is rich in haplotypes.5. Morphologic and molecular levels, L.Chinense, genetic variation had significant geographic disintegration in the East and West of China. The genetic diversity of western populations was higher than the eastern's. Therefore, high genetic diversity populations should have the priority in situ conservation, but also to consider the ex-situ conservation. For hybrid breeding of parent selection, the emphasis on provenance selection is an important way to improve breeding efficiency.