光叶珙桐的等位酶分析及其生物地理学意义

采用水平切片淀粉凝胶电泳实验方法，对光叶珙桐(Davidia involucrata var．vilmoriniana)4个居群、78个个体、11种酶系统，21个位点进行了等位酶分析。各居群的多态位点百分比P＝28.6％-47．6％，实际杂合度Ho＝0．177—0.308，平均每个位点的等位基因数A=1．3-1．6。在变种水平上，多态位点百分比P＝52．4％，平均每个位点的等位基因数A＝1．8，实际杂合度Ho＝0．272，期望杂合度Ho＝0．216。基因分化系数FST＝0．1928，说明光叶珙桐居群问分化小。各项指标表明光叶珙桐的遗传多样性水平较高，比原变种珙桐高，外部环境可能是影响珙桐分布格局的重要因素。昭通与宝兴的遗传多样性明显高于其他两个居群，遗传多样性保存较为完整，而处于分布区东、西两侧边缘(云南西北部和湖北五峰)遗传多样性则相对较低，推测四川盆地边缘山地是该种的遗传多样化中心，可能是在地质灾难中(如第四纪冰期)，光叶珙桐真正的避难所。分布区东西两侧的居群可能是从四川盆地边缘山地扩散而来。

Allozyme Analysis of Davidia involucrata var.vilmoriniana and Its Biogeography Significance

Allozyme analysis of Davidia involucrata var. vilmoriniana was carried out with 78 individuals in four populations by means of horizontal starch gel electrophoresis technique.Eleven enzyme systems and 21 loci were investigated.The results show that there is high genetic diversity in Davidia involucrata var. vilmoriniana .At population level,the percentages of loci polymorphic( P ) are variable from 28 6%-47 6%.Mean numbers of alleles per locus ( A ) are variable from 1 3 to 1 6.Observed mean percentage of loci heterozygous ( H o ) is variable from 0 177 to 0 308.At var.species level, P =52 4%, A =1 8, H o =0 272, H e =0 216, F st =0 1928,which means that the genetic difference among population is a little higher than Davidia involucrata var. involucrata .The genetic diversity of Zhaotong (NE Yunnan) and Baoxing (W Sichuan) are higher than that of the other two populations.This means that these places might be the really refuges during geological disaster (such as glacial age in Quaternary).The populations occurring in the eastern and western margins of the distribution area might be migrated from the refuges.