基于叶绿体DNA单倍型的蒙古沙冬青遗传多样性格局探究

Study on Distribution Pattern of Genetic Diversity of Ammopiptanthus mongolicus Based on the Haplotype of Chloroplast DNA

为保护第三纪孑遗种质资源蒙古沙冬青(Ammopiptanthus mongolicus),使用叶绿体非编码片段psbC-trnS对蒙古沙冬青9个野生居群的cpDNA进行测序,分析中国内蒙古阿拉善左旗和鄂尔多斯高原地区范围内,不同居群间的叶绿体非编码区序列差异以及沙冬青的遗传多样性格局。结果表明:排序后的序列总长度为1 493～1 545 bp,共计110个变异位点,根据序列变异位点共确定出12种单倍型,其中H2单倍型分布最广。通过单倍型建树和单倍型网络分析推测出单倍型H2为可能的祖先单倍型。物种水平上单倍型多样性(Hd)指数为0.297 48,核苷酸多样性(π)指数为0.001 66;居群水平上Hd指数介于0～0.813 19之间。总的遗传多样性Ht为0.309 (0.090 3)高于居群间基因多样性Hs为0.293 (0.078 4),基因交流大部分在居群内部。居群间的遗传分化系数NST=0.018小于GST=0.053 (p>0.05,不显著),表明居群不存在明显的谱系地理结构。中性检验结果认为内蒙古西部地区沙冬青居群拒绝中性进化,群体历经扩张或者基因座位受到负选择作用,符合古老孑遗种说法。通过遗传变异分析提出内蒙古特有种沙冬青的保护策略,进一步的保护建议为实施就地保护、迁地杂交等措施。

Study on genetic diversity of geographical distribution of Ammopiptanthus mongolicus and put forward the protection strategy in Alxa Left Banner and Erdos Plateau of China.The cpDNA sequences of 9 populations of Ammopiptanthus mongolicus in Mongolia were sequenced by non-coding fragment psbC-trnS of chloroplast,and the sequence differences of non-coding region among different populations were analyzed.The results showed that the total length of the sequence after sequencing is 1 493~1 545 bp,with a total of 110 variation sites.According to the sequence variation site,12 haplotypes were identified,of which the H2 haplotype was the most widely distributed.Haplotype H2 was found to be a possible haplotype of ancestral haplotype by haplotype construction and haplotype network analysis.At species level,haplotype diversity(Hd)index is 0.297 48,nucleotide diversity(Pi)index is 0.001 66,and population level Hd index is 0~0.813 19.The total genetic diversity(Ht)is 0.309(0.090 3)higher than that of interpopulation genetic diversity(Hs)is 0.293(0.078 4),this result indicates that the gene exchange among populations is very less.According to the sequence,the coefficient of genetic differentiation Nst=0.018 between populations is less than Gst=0.053(p>0.05,not significant),indicating that there is no obvious phylogeographic structure among populations.Neutral test result shows that the western region of Inner Mongolia Ammopiptanthus mongolicus populations refuse neutral evolution.Population expansion has happened in the specie and the mutation of this specie has been effected by negative selection effects.This phenomenon corresponds to the theory of ancient relic species.Further protection is recommended for the implementation of the on-site conservation and off-site preservation methods and other measures.