高山嵩草种群在放牧干扰下遗传多样性的变化

GENETIC DIVERSITY OF KOBRESIA PYGMAEA POPULATIONS ALONG A GRAZING GRADIENT

利用SRAP(Sequence-related amplified polymorphism)分子标记,对放牧干扰下的高山嵩草(Kobresia pyg-maea)种群进行了遗传多样性研究,获得了下述结果:1)20对SRAP引物组合共检测出448条清晰条带,其中376条条带具有多态性,多态位点百分率为83.93%,随着放牧强度的增加,高山嵩草种群多态位点百分数、Nei's遗传多样性指数、Shannon信息指数均下降。2)高山嵩草种群具有较高的遗传多样性和较低的遗传分化(总的遗传多样性Ht为0.2766,种群内遗传多样性Hs为0.2436,遗传分化系数Gst为0.1194,基于Gst估计的基因流Nm*为1.8434),但随着放牧强度的增加,Gst增加,Nm*降低,说明放牧限制了种群间的基因交流,使种群发生遗传分化。3)不同放牧梯度的高山嵩草种群间的遗传距离很小,但是随着放牧强度的增加,种群间的遗传距离逐渐增加,遗传一致度降低。根据遗传距离所构建的UPGMA聚类图中高山嵩草4个种群随着牧压的增加,逐级聚在一起。

Aims Our objective was to explore differences in genetic diversity of Kobresia pygmaea populations related to grazing intensity to help prevent grassland degradation and contribute to ecology,genetics and evolutionary ecology. Methods We randomly selected tender leaves from 25 K. pygmaea individuals from four populations along a gradient of grazing intensity,used SRAP （Sequence-related amplified polymorphism） molecular markers,and examined the genetic diversity of the populations to determine the effect of grazing disturbance. Important findings We used 20 primers and produced 448 clear bands, 376 （83.93%） of which were polymorphic. With increased grazing intensity, the percentage of polymorphic loci, Nei＇s genetic diver- sity index and Shannon information index of the K. pygmaea populations decreased. Total genetic di- versity （Ht） of the four populations under different grazing intensities was 0.276 6, genetic diversity within the four populations （Hs） was 0.243 6, genetic differentiation coefficient among populations （Gst） was 0.119 4 and gene flow （Nm＊） was 1.843 4. With increased grazing intensity, Gst increased and gene flow decreased. Therefore, grazing increased genetic the differentiation coefficient among populations, restrained gene transfer among populations and promoted population gene differentiation. The genetic distance of the four populations with different grazing intensities was small; however, with increased grazing intensity, genetic distance slowly increased and genetic consistency among populations decreased. The UPGMA dendrogram constructed by genetic distance arrayed the four populations in order of increasing grazing pressure.