Phylogeography Of The Desert Plant Haloxylon Ammodendron

Climate fluctuations,aridification and desert expansion in the arid regions of Northwest China have had an important impact on the geographical distribution,inheritance and evolution of the widely distributed arid desert plants.In this study,we selected desert plant H.ammodendron and the sandy plant H.persicum in the desert area of Northwest China,and studied the biological taxonomic status of H.ammodendron.Based on the two genes of cp DNA and nr DNA,the genetic differentiation and species delimitation of H.ammodendron and H.persicum distributed in China were studied;Analysis of the ecological niche differentiation of niche differentiation and its impact on species evolution.Based on the sequence of chloroplast gene spacer,to explore the genetic variation distribution,dynamic history and phylogeographic structure of different natural populations of H.ammodendron.The main results as following:1.Study on biological classification of H.ammodendron based on ITS and cp DNA sequencesIn this study,we selected three cp DNA(trn S-trn G,rps4 and trn V)sequences and two nr DNA(ITS2,ITS1-ITS4)sequences,to analysis of 30 individuals of H.ammodendron and H.persicum distributed in the same southern margin of the Gurbantunggut Desert.The results show:(1)Using ITS and cp DNA sequences,The biological classification of H.ammodendron was clear,and the genetic differentiation was obvious.;(2)Both the ITS and cp DNA sequence combinations could be used as DNA barcode sequences to identify H.ammodendron and H.persicum;(3)There was no evidence for an ecological niche differentiation between H.ammodendron and H.persicum,and ecological factors did not play a significant role in the divergence and evolution of the two species,and the two species were likely to have similar evolutionary history.2.Phylogeography of the H.ammodendronThrough field investigation,a total of 233 individuals from 23 populations of this species were collected.The collection area basically covers the natural distribution area of the H.ammodendron.Through the screening of chloroplast DNA polymorphisms in the early stage,two pairs of chloroplast sequences(trn S-trn G,trn V)were selected in this study..The results showed that:(1)Twenty mutation sites were detected by cp DNA sequence combination and 21 haplotypes were identified.H.ammodendron has a high genetic diversity(h _T=0.842);(2)The population genetic differentiation index N_ST(0.658)was significantly higher than G_ST(0.554)(P<0.01),indicating that there is a significant phylogeography structure in the natural distribution range;(3)AMOVA analysis showed that most of the genetic variation(65.7%)came from the population;(4)Both ML and Bayesian phylogenetic trees based on cp DNA sequence combination have high posterior probabilities.The haplotype is divided into three phylogeography branches,Xinjiang,Inner Mongolia,Gansu and Qinghai;(5)The neutrality tests and mismatch distribution of H.ammodendron showed that recent population expansion occurred in the Xinjiang,Gansu and Inner Mongolia regions.This study is based on the combination of ITS and cp DNA sequences.The biological classification of H.ammodendron and H.persicum were clear,and the genetic differentiation were obvious..Both the ITS and cp DNA sequence combinations could be used as DNA barcode sequences to identify H.ammodendron and H.persicum.There was no evidence for an ecological niche differentiation between H.ammodendron and H.persicum,and ecological factors did not play a significant role in the divergence and evolution of the two species,and the two species were likely to have similar evolutionary history.Based on the cp DNA sequence(trn S-trn G,trn V),the H.ammodendron population has high genetic diversity,and there is a significant phylogeography structure.The haplotype is divided into three phylogeography branches,Xinjiang,Inner Mongolia,Gansu and Qinghai.The population groups distributed in Xinjiang,as well as the population groups in Gansu and Mongolia,have experienced population expansion,which may be caused by climate fluctuations,aridification and desert expansion in the arid northwestern Quaternary.The conclusions of this study can provide important theoretical basis and data support for the phylogeny,genetic and evolution of H.ammodendron and H.persicum.