| Xanthoceras sorbifolium Bunge(yellowhorn) is the single species within the family Sapindaceae, which is ditributed in Qinghai, Gansu, Shaanxi, Henan, Shanxi and Hebei, China. It is an important economic plant, with 57.18 % of kernel oil, which can be used for cooking or industrial use. Besides, the chemical compounds in shell, stem and leaf, such as triterpenes, are potentially valuable for developing new medicines against Alzheimer’s and cancer. We have taken a field trip to all areas that may appear yellowhorn, and collected a large number of wild yellowhorn information, germplasm and molecular materials, to provide the scientific basis for better protection and utilization of the plant. In order to provide the scientific basis for better protection and utilization of yellowhorn, the potential habitats were investigated and plant samples were collected for germplasm reservation and molecular analysis.5 cpDNA intergenic spacers(trnL-trnF, trnD-trnT, trnH-psbA, trn S-trn G, rpl32-trn L) in 399 individuals from 38 populations were employed for phylogeography study. The main results were as follows:(1) North China was the origin of yellowhorn. This area used to be dry and hot in the cretaceous period. Therefore yellowhorn was a tropically origined. During that time, it had been able to withstand the hot and dry climate. After a long time, it adapted to cold climate, and survived in the northern China.(2) We detected a strong cpDNA phylogeography patter between populations(Gst=0.738, Nst=0.890 and Nm=0.03). This was supported by phylogenetic trees(calculated by MP, ML and Bayes) were all built into 5 clades showing obvious geographic distribution patterns.(3) The speciation of yellowhorn was linked with the geological movement of Mountain Yan, the Qinling orogeny and its special ecological niche. Therefore, yellowhorn ancestors were isolated to a relatively small region, creating its own unique ecological niche.(4) The differentiation between main cpDNA haplotypes of yellowhorn was closely linked with the uplift of Mountain Lvliang and Mountain Ziwuling and the outflow of the Paleo-Sanmen Lake. Seed flow between Yellowhorn populations can be blocked effectively by mountains and rivers.(5) With the uplift of the Mountain Lvliang, a "closed" area was formed, lasting for a long period of time. In this area, a special cpDNA genetype gradually formed. However, the uplift of the Mountain Lvliang had never stopped. the enclosed area gradually broken, resulting in the formation of more complex cpDNA haplotype distribution patterns in this area.(6) There were several refugia in northern China during the last glaciation. These areas were located in midwestern and eastern of Mountain Qinling, southern Mountain Ziwuling Mountain Huanglong, Mountain Lvliang,Xinzhou Basin, Taiyuan Basin and Zhangjiakou Basin respectively. Midwestern of the Qinling Mountain was the youngest refugia among these.(7) There were two sudden demographic expansion(Haplotype E4 and E8) on the Loess Plateau, which was closely related to the formation of the Loess Plateau.Predeicted by MaxEnt model, the vast majority of suitable habitat for yellowhorn were located in the northern Mountain Qinling and Huaihe River. In southern Mountain Qinling, the potential habitats were mainly located in the Tibet Autonomous Region and Sichuan Province. The most suitable areas for large-scale cultivation are Shaanxi Province, Henan Province and Shandong Province for fruit production.Xanthoceras sorbifolium should be included in the national protected plants list. Tongchuan City, Huanglong County, Jiaokou County, Fangshan County, Fanshi County and Yuxian County are important protection areas, where yellowhorn was abundantly distributed with a high genetic richness. In addition, yellowhorn germplasm bank should also be established, focusing on the germplasm resource collection from forementioned areas as well as Shanxian County, Taiyuan City, Lixian County and Baoji City. |
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