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Population Ecological Genetics Of Reaumuria Soongorica (Pall.) Maxim In The Oasis-Desert Ecotone In Fukang, Xinjiang, Revealed By ISSR Markers

Posted on:2007-06-11Degree:MasterType:Thesis
Country:ChinaCandidate:Z Q QianFull Text:PDF
GTID:2120360182495167Subject:Ecology
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Reaumuria soongorica (Pall.) Maxim, which belongs to the genus Reaumuria L. in the family Tamaricaceae, is an ultra-xeric subshrub species with characteristics such as drought- and salt-tolerances. It is also a founder and dominant plant species widely distributed in China's temperate desert areas. However, as a result of natural events and human activities, R. soongorica grasslands have been undergoing degradation and sandification, and thus need urgent restoration and reconstruction.By using ISSR markers, studies have been performed to reveal the population genetic diversity and structure of R. soongorica in the oasis-desert ecotone in Fukang, Xinjiang. Eleven primers were screened to amplify DNA sequences from 132 individuals, which corresponded to seven subpopulations. Totally, 176 loci, all of them polymorphic, were detected, and the percentage of polymorphic loci (PPB) was 100%, which meant that there existed a relative high genetic diversity within the R. soongorica population.According to the results of AMOVA analysis and the analyses of Nei's gene diversity and Shannon's information index, the percentages of genetic variation among subpopulations were 15.87%, 14.58% and 16.28% respectively, which meant that between 83.72% and 85.42% of total genetic variation occurred within subpopulations. Besides, Popgene analysis also revealed a relatively high gene flow (N_m = 2.9290) among subpopulations, almost equaling the mean value of widespread plant species (N_m = 3.03). And it was high enough to resist the effects of genetic drift and prevent local differentiation.Correlation analysis showed that there existed no significant correlation between the ISSR-based genetic diversity of the seven R. soongorica subpopulations and their ecological factors (mainly in soil) (P > 0.05). However, on the other hand, Mantel test revealed a remarkably significant correlation between inter-subpopulational geneticdistances and geographic distances (r = 0.637, P < 0.01), indicating that geographic distance was among the important factors affecting the population genetic structure of R. soongorica.Meanwhile, a comparison was conducted between the results based on ISSR and RAPD markers respectively, and revealed obvious differences between them. For example, Mantel test showed no significant correlation between ISSR- and RAPD-based Nei's genetic distance matrices (r = 0.351, P = 0.079). Also, in terms of Shannon's information index and Nei's gene diversity index, RAPD markers revealed higher genetic diversity and differentiation than ISSR markers. These differences have probably been caused by the different evolutionary patterns of the genomic regions sampled by ISSR and RAPD markers. ISSR markers are probably neutral or nearly neutral, so they are free from or just slightly influenced by external selection forces, while RAPD markers (at least part of them) are significantly affected by such forces.
Keywords/Search Tags:Reaumuria soongorica (Pall.) Maxim, Genetic structure, Oasis-desert ecotone, Inter-simple sequence repeats (ISSR), Neutral markers
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