Phylogenetic Relationship And Character Evolution Study Of Zygophyllum(Zygophyllaceae) Members In China

Object: Now there are many achievements about Zygophyllum have been made by scientists, but the adaptive evolution study of Zygophyllum members in China is barely reported; and studies about this genus are focused on Nei Meng Gu and Gan Su, but Xing Jiang as the distribution area of most Zygophyllum species, is not been noticed. The vegetation in Xing Jiang has a high research value by reason of its unique arid and semiarid climate characteristics. In this study, using the knowledge of phylogenetic to discuss evolutionary processes of Zygophyllum members and the important influence caused by the environmental factors in those processes, and try to investigate some issues that have not been noticed.Methods: Phylogenetics of 14 Zygophyllum members in China were analyzed using DNA barcode technique; trn L-F、rbcl、ITS 、mat K、trn H and ycf1 gene was amplified by the PCR process and sequencing separately. Meanwhile, download DNA barcode sequences of overseas species from Gene Bank. Using phylogenetic softwares construct phylogenetic trees. Get morphological characters data of Chinese Zygophyllum members by actual measurement, and overseas species by internet specimen database. After that, collationing characters data and constructing data matrix for correlation analysis by SPSS and R software. Combine with phylogenetic trees, we analysis the phylogenetic signal of morphological characters, the evolution speed of Zygophyllum species and reconstruct ancestral state of some characters.Results: All China Zygophyllum species clustered into one major clade with 73%believing rate, and constitute sister clades with southern African species There are obvious differences between species distributed in South Africa, Namibia and Australia. The distribution range of Chinese Zygophyllum members are corresponded to the the close affinity relationship between Zygophyllum species distributed in countries of Central Asia. Strong phylogenetic signals were observed in four traits: Nature of branches, Leaves arrangement, Life cycle and Petiolule(K>0.5). Sepal length,sepal width,pollen types,stem natural,leaf structure and other 5 morphological characters of China Zygophyllum species are different from foreign species significantly(P<0.05); Significant phylogenetic signals were observed in the life cycle, leaves arrangement, leaf shape and other 5 morphological characters(P<0.05); The result of reconstruct ancestral state of characters shows that: one pair leaflet character is the ancestral state, two or multiple pair leaflet are evolved from ancestral state; the ancestral state of leaf shape is not very clear, but species wiith similar leaf shape clustered into same clades indicate that there is no interference between evolution process of different clades.Conclusion: The phylogenetic position and evolution speed of Zygophyllum members in China was determined in this study; differences of morphological characters were found between Chinese and foreign Zygophyllum species; Since Zygophyllum members began to expand, while opened the distance between traits of species in Africa and China. After adaptive evolution, Zygophyllum members in China have got unique morphological features. Through the analyze of ancestral state in this study, we conjecture that Zygophyllum members in China were appear after the retreat of Tethys during the early Quaternary Period. In general, this study will provide some theoretical references about phylogenetic research of Zygophyllum members in the future.