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Genetic Characteristics And Conservation Strategies Of Haloxylon Ammodendron Populations In Desert

Posted on:2021-04-05Degree:MasterType:Thesis
Country:ChinaCandidate:B WeiFull Text:PDF
GTID:2370330620972840Subject:Biology
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Genetic Haloxylon ammodendron is a kind of super arid arbor belonging to Haloxylon of Chenopodiaceae.As the main constructive species in the desert area of Northwest China,H.ammodendron plays an important role in maintaining the biodiversity of desert ecosystem.At present,due to the influence of natural factors and human activities,H.ammodendron community in the desert area of Northwest China has been degraded and even died in a large area.The genetic research of H.ammodendron is helpful to understand the genetic diversity and structure of H.ammodendron,to clarify the spatial distribution characteristics and differentiation mechanism of genetic variation of contemporary population of H.ammodendron,to reveal the regional environmental differences and the impact of human activities on the genetic diversity and structure of H.ammodendron,and to provide the basis for formulating scientific protection strategies.In this study,the genetic diversity and genetic structure of 36 populations and 420 individuals of H.ammodendron were analyzed by using two chloroplast?cpDNA?fragments and one ITS fragment in the desert area of Northwest China.The main conclusions are as follows:1.The total level of genetic diversity in the population of H.ammodendron was higher,but the level of genetic diversity in the population was lower.24 haplotypes were detected based on cpDNA sequence,16 ribotypes were detected based on its sequence.According to their genetic relationship and geographical distribution,they can be divided into three geographic groups,namely,western group,Eastern Group and southern group.At the species level,the genetic diversity of H.ammodendron,was higher?HT>0.8?,but lower in population?HS<0.35?.At the population level,the results of cpDNA data showed that the population genetic diversity of the western group was the highest,especially that of Fangcaohu,Qitai and Burqin,while ITS data showed that the population genetic diversity of the eastern group was high,especially that of Ulan Buhe desert,Alxa Zuoqi and Dengkou.The analysis of molecular variance based on cpDNA and ITS showed that the genetic variation of H.ammodendron population mainly came from the population?cpDNA:77.81%;ITS:84.20%?,which may be due to the limited transmission of seeds and pollen within a short distance.2.There was strong genetic differentiation among different geographical groups of H.ammodendron.The total genetic diversity?HT?is much higher than that of average genetic diversity in population?HS?,which indicates that there is obvious genetic differentiation(FST>0.9)between groups.The landscape genetic analysis based on cpDNA and ITS data also shows that the level of genetic differentiation among groups were high.The results of niche consistency test showed that there was obvious niche differentiation between the groups in the western group and the other two geographical groups,but no obvious niche differentiation was detected between the eastern group and the southern group.The results of PCA and ANOVA showed that the temperature seasonality,min temperature of coldest month,precipitation of driest month and precipitation seasonality were the main environmental factors that caused the niche differentiation between the western group and the other two geographical groups.The differences of ecological environment in different geographical groups lead to significant differences in genetic structure of different groups.Qilian Mountain and Altun mountain are the biggest genetic barriers between the eastern and southern groups.Altun mountain and Qilian mountain rose rapidly in the Middle Pleistocene,which coincided with the differentiation time between the eastern and southern groups of H.ammodendron?cpDNA:1.18Ma;ITS:1.20Ma?.It is speculated that the rapid uplift of Qilian Mountain and Altun Mountain limits the gene exchange between the two regions,and the long-term geographical isolation promotes the genetic differentiation between the eastern group and the southern group.3.The key genetic protection area of H.ammodendron is in the southern edge of Gurbantunggut Desert of Xinjiang.Based on the genetic diversity data,combined with the environmental factors and the current land use/land cover data analysis in the northwest desert area,it is found that the genetic diversity level of H.ammodendron population in the southern edge of Gurbantonggute desert in Xinjiang is high and the habitat is good,especially in Karamay,Manas,Fukang,Qitai and other areas,which should be the key areas of H.ammodendron genetic protection.In order to collect the gene resources to the greatest extent,we should collect them in the whole distribution area when designing the sampling strategy.We should focus on the collection of H.ammodendron germplasm resources in Shawan County,150 regiments,burjin County of Xinjiang,Guazhou County of Gansu,Dengkou County,Jilantai of Inner Mongolia and Tuosu lake of Qinghai.
Keywords/Search Tags:Haloxylon ammodendron, genetic diversity, genetic structure, environment driven, conservation strategy
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