The data was analyzed with three softwares : tfpga popgene32 and amova155 which are tools for molecular analysis . the percentage of polymorphic sites at species level was 86 . 93 % , and they were 83 % 68 % and 80 % at population level . nei " s gene diversity index was 0 但长叶榧还保留了较高的遗传多样性：物种水平的nei氏基因多样度指数达到0 . 2479 ， shannon信息指数也达到了0 . 3807 ，而其物种水平的多态位点百分率高达86 . 93 。
2.
So it was enlightened that t . jackii still had a high level of genetic diversity . the similar index between the t . jackii populations from jiangshi nature reserve and xufan reservoir was higher than that between the populations from jiangshi nature reserve and xufanggeng . it was determined by geographical factors 聚类分析表明将石自然保护区的长叶榧居群与许坊水库的相似系数较大，而和许坊埂的相似系数较小，这和地理上将石自然保护区和许坊水库邻近，而许坊埂距前两者较远的事实相符。
3.
Several results were concluded : firstly , the population of t . jackii was decreasing sharply and its living area was contracting , so the percentage of genetic variance among t . jackii populations was lower than that within its population ; secondly , its genetic diversity index was relatively high ; thirdly , according to its gene flow index , the population disintegration of the species could be prevented by genetic communication among populations of the species ; finally , the similar index between the populations from jiangshi nature reserve and from xufan reservoir was higher than that between the populations from jiangshi nature reserve and from xufanggeng , corresponding with the fact that it is nearer between jiangshi nature reserve and xufan reservoir than that between jiangshi nature reserve and xufanggeng 2 、长叶榧的遗传多样性分析，分析了多态位点百分率( percentageofpolymorphicsites ) 、 nei氏基因多样性指数( nei ’ sgenediversityindex ) 、 shannon信息指数( shannon ’ sinformationindex ) 、居群间的相似系数( geneticsimilarityindex )和遗传距离( geneticdistance ) 、遗传变异在居群间和居群内的分布( thepercentageofvarianceamongandwithinpopulation )及基因流( geneflow ) 。结论是：分布在群体间的遗传变异较分布在群体内的遗传变异小，说明该生物的分布范围越来越狭小。
