热带亚洲北缘高山榕亲缘地理学初探

Phylogeography of Ficus altissima in the Northern Edge of Tropical Asia

【目的】探讨热带亚洲地区乔木种的谱系地理分布格局及其演化历史。【方法】以热带雨林群落代表乔木种高山榕为研究对象,采集了热带亚洲大陆北缘25个高山榕种群177个个体,采用叶绿体DNA (cpDNA)片段psbA-trnH测序的方法,对其遗传多样性、种群结构及种群历史动态进行分析。【结果】高山榕种群遗传多样性较低(HT=0.378),只得到3个psbA-trnH单倍型,然而其中2个祖先单倍型被高山榕与近缘种共享。两两种群间遗传分化值FST在0.000~1.000之间,基因流水平低(Nm=0.260),97.8%的遗传变异来自于种群间,但不存在明显的亲缘地理结构[GST (0.887>NST (0.799)]。分子进化中性检验结果表明:自然选择在分子进化过程中未发挥重要作用,而失配分析显示为单峰分布。【结论】综合中性检验、失配分析以及物种分布模型结果,显示高山榕经历了缓慢的种群扩张过程,而有限的种子散播能力可能限制了种群间的基因流,导致高山榕种群扩张缓慢。

[Purpose]To investigate the phylogeographic structure and its evolutionary history of the tree species distributed in tropical Asia.[Method]177 Ficus altissima individuals from 25 populations were sampled in present study,mainly in the northern edge of tropical Asia.F.altissima is listed as one of the dominant species in Asian rainforest.The cpDNA fragment psbA-trnH was sequenced to explore the genetic diversity,population genetic structure and dynamics of F.altissima.[Result]A low level of genetic diversity(HT=0.378)was revealed and only three psbAtrnH haplotypes were identified from the 25 populations totally.However,two ancestral haplotypes were shared by F.altissima and its related species.The population pairwise genetic differentiation(FST)ranges from 0.000 to 1.000.Low levels of gene flow(Nm=0.260)were found among populations and 97.8%of the total genetic variance was distributed among populations.The GST(0.887)was higher than NST(0.799),showing that there was no significant phylogeographical structure.Test of neutral evolution revealed no deviation from mutation drift equilibrium,while mismatch analysis showed unimodal.[Conclusion]Combined results of neutrality test,mismatch analysis and species distribution modeling indicated that the populations of F.altissima could have undergone a slow expansion in its evolutionary process.The limited seed dispersal could have resulted in the low gene flow and slowed the population expansion.