环境因子对中国柽柳遗传变异的影响

Effects of environmental factors on population genetic diversity of Tamarix chinensis

分别以核糖体DNA(nuclear ribosomal DNA,nrDNA)的内转录间隔区(internal transcribed spacer regions,ITS)和两条叶绿体DNA(chloroplast DNA,cpDNA)片段—trnL-trnF,rps 16为分子标记,研究了20个自然分布的中国柽柳群体遗传变异与环境因子和地理距离间的相关性。结果表明:ITS序列(616 bp)中共发现了10个多态位点,定义了11种单倍型;总核苷酸多样性和总单倍型多样性分别为2.170和0.814。两个cpDNA分子标记片段的拼接序列(1542 bp)中共发现了14个多态位点,定义了16种单倍型,总核苷酸多样性和总单倍型多样性分别为0.500和0.586。ITS遗传多样性与地理、气候和土壤因子间相关性分析显示:海拔、温度和经度是影响中国柽柳群体遗传变异的主要因素。在低海拔、温暖和靠海近的湿润东部群体,ITS遗传多样性较高。而cpDNA的遗传变异与各种环境因子间没有显著的相关性。Mantel检测发现中国柽柳ITS的遗传变异与地理距离显著正相关,而cpDNA的遗传变异没有显著的地理渐变趋势,该结果进一步揭示了中国柽柳强大的种子流在降低群体间遗传分化上发挥了重要作用。

In this study,we examined the relationships between environmental factors and the genetic diversity of 20 Tamarix chinensis.populations throughout its native range.Genetic diversity was evaluated by comparing the sequences of nuclear ribosomal internal transcribed spacer regions(ITS)and two chloroplast DNA(cpDNA)regions(trnL-trnF and rps16).Eleven haplotypes were identified on the basis of 10 variable sites within the 616 bp sequenced ITS region,and the total nucleotide diversity and haplotype diversity indexes were 2.170 and 0.814,respectively.Sixteen haplotypes were identified on the basis of 14 variable sites within the two chloroplast regions(1542 bp),and the total nucleotide diversity and haplotype diversity indexes were 0.500 and 0.586,respectively.The results showed that the genetic diversity based on the ITS region is influenced mainly by altitude,temperature,and longitude.Populations with rich genetic diversity exist at lower altitudes,in warmer habitats,and in eastern regions nearer to the sea.We detected no significant relationships between the genetic diversity of cpDNA and environmental variables.Using the Mantel test,a significant relationship was detected between matrices of ITS genetic differentiation and matrices of geographical distance,but this relationship was not detected from the cpDNA data.This result further proved that seed flow is an important factor contributing to the low genetic differentiation of T.chinensis populations.