Phylogenetic Evolution Of Buckwheat And Response Of Its Distribution To Climate Change

In this study,wild buckwheat resources in their origin center regions were investigated.The phylogenetic relationship of wild buckwheat species was studied by ITS,matK and psbA-trnH sequences.Buckwheat species were classified based on molecular and classical morphological evidences.In addition,based on 1506 distribution points and 19bio-environmental factors,the MaxEnt model was used to predict the potential habitats of wild buckwheat in its origin center regions in the 2050s and 2080s with three representative concentration paths(RCP2.6,RCP4.5,RCP8.5).The response of wild buckwheat distribution in its origin center regions to climate change was discussed in order to provide a reference for further conservation and sustainable utilization of buckwheat plants.The research results were as follow:(1)Wild buckwheat is annual plant.Most of them were perennial herbs or semi-shrubs.The stem is slender and the plant type is mainly erect.The leaf shape is triangular,heart-shaped,oval,hastate and linear.Inflorescence is raceme,corymbose or spike,terminal or axillary,white and pink flowers,5 perianths and oval perianth.The seed is mostly triangular in shape and most of them are exposed outside the persistent perianth.Moreover,in terms of growth environment,wild buckwheat is suitable for growing in neutral-alkaline soil among which F.leptopodum and F.jinshaense are more prominent.(2)After comparison,the ITS sequence length of 22 wild buckwheat species was 647 bp,the matK sequence length was 1163 bp and the psbA-trnH sequence length was 442 bp.Three DNA barcodes were able to successfully identify the buckwheat species and the outer group.Based on the phylogenetic trees constructed by three DNA barcodes,all buckwheat species could be divided into two subgroups:one subgroup including F.tataricum,F.esculentum and F.cymosum and the other wild buckwheat was clustered into another subgroup.Therein,the trnH-psbA could not distinguish the relationship between wild buckwheat well due to its insufficient sequence information.Moreover,molecular evidence supported the closer relationship between F.tataricum and F.cymosum.Besides,F.wenchuanense,F.qiangcaiense and F.callianthum wild buckwheat were mainly clustered,which indicated that the three wild buckwheat species were closely related.(3)In the current climate,main environmental variables affecting the distribution of wild buckwheat were Bio12(annual average precipitation),Bio19(average precipitation in the coldest season),Bio6(lowest monthly temperature),Bio10(average temperature in the warmest season),Bio3(isotherm),respectively accounted for 34.6%,14.6%,14.6%and 13.7%and cumulative contribution rate was 77.5%.Besides,the distribution range of wild buckwheat in its origin center regions mainly included the western of Sichuan province,the northeast of Yunnan province and the west of Guizhou province.The suitable area was1.38×10~5 km~2,low suitable area was 1.56×10~5 km~2 and non-suitable area was 23.6×10~5 km~2,accounting for 5.18%,5.88%and 88.94%of the total area respectively.(4)In the 2050s and 2080s,Bio12 had the greatest contribution rate in three representative concentration paths(RCP2.6,RCP4.5,RCP8.5),which indicated that the most important environmental variable affecting the potential suitable habitats of wild buckwheat plants was annual average precipitation.In the 2050s,the suitable areas of RCP2.6,RCP4.5and RCP8.5 were 1.50×10~5 km~2?1.27×10~5 km~2?1.19×10~5 km~2,accounting for 5.65%,4.78%and 4.48%of the total area,respectively.In the 2080s,the suitable areas of RCP 2.6,RCP 4.5and RCP 8.5 were 1.34×10~5 km~2?1.49×10~5 km~2?1.48×10~5 km~2,accounting for 5.06%,5.59%and 5.00%of the total area,respectively.Compared with the current climate,the suitable area of wild buckwheat was predicted to decrease.Therefore,the decrease of suitable areas of wild buckwheat might lead to the decrease of species diversity,especially some species with narrow distribution range were at risk of extinction.