【摘要】 森林片断化是造成全球生物多样性丧失的主要原因,但从种群遗传学角度开展的研究还远远不够。因此,本文采用ISSR(inter-simplesequencerepeat)方法对广东省鼎湖山、黑石顶、大雾岭、古田、萝岗和饶平6个地点的南亚热带片断化森林中的厚壳桂(Cryptocaryachinensis)种群的遗传多样性进行了研究。每个种群分成体、小树和幼苗3个年龄级采样,共采集厚壳桂样品448个。7个ISSR引物共扩增出209条多态性带。研究结果表明,6个厚壳桂种群的总遗传多样性为0.1529,种群平均遗传多样性为0.0537。和保护较好的厚壳桂种群相比,萝岗和饶平的两个村边林种群的遗传多样性较低。6个厚壳桂种群间的遗传分化系数(GST)为0.6489。AMOVA分析结果表明,总的遗传变异中,67.97%(P<0.0002)的遗传变异存在于种群间,2.06%(P<0.01)的遗传变异存在于不同年龄级之间,29.96%(P<0.0002)的遗传变异存在于种群内。基于遗传距离的UPGMA分析结果表明,6个厚壳桂种群大致分成两支:一支包括大雾岭和黑石顶2个种群,另一支包括其他4个种群。鼎湖山、古田、大雾岭和黑石顶不同年龄级均各自聚合在一起。可以看出,森林的破碎化导致了南亚热带厚壳桂种群遗传多样性降低,种群间基因流受阻,提示我们对于同一地区的易危物种,这种威胁将很大,急需开展相关的保护研究。更多还原

【Abstract】 Forest fragmentation is the main threat to global biodiversity. However,genetic information con-cerning the effects of fragmentation is currently lacking for plant species in lower subtropical China. To en-rich scientific understanding of this issue,we employed the ISSR (inter-simple sequence repeat) markers to determine the genetic structure in Cryptocarya chinensis. Four hundred and forty-eight individuals from six fragmented populations in Guangdong Province were sampled according to age classes. Four of these popu-lations,DHS,HSD,DWL and GT,were in nature reserves,and the other two,LG and RP,were near villages. Seven ISSR primers produced a total of 209 polymorphic bands which were used to evaluate genetic varia-tion. The results showed that C. chinensis displayed unexpectedly low genetic variation within populations (HP =0.0537) and high genetic differentiation among populations (GST=0.6489,φST=0.6797). Genetic varia-tions in LG (0.0251) and RP (0.0000) populations were lower than in the other four well-conserved popula-tions. Considering age classes,low but significant genetic differentiation characterized DHS and HSD popu-lations. These results indicate that C. chinensis has experienced a recent decrease in population size which may cause a bottleneck effect. The resulting fragmentation increased genetic drift and inbreeding,causing theloss of genetic variation. Our results for C. chinensis may be general for other species in this area and there-fore more work related to conservation is urgently needed.更多还原