Chloroplast DNA Phylogeography Of Dipteronia Sinensis Oliv

The genus Dipteronia Oliv. (Aceraceae) is endemic to China and consists of only two species, Dipteronia sinensis Oliv. and Dipteronia dyeriana Henry. Dipteronia is one of the ancient relic woody genera in the floristic region of North Temperate Zone. Both species are rare and endangered,are only found in Shaanxi, Gansu, Henan, Hubei, Hunan, Sichuan, Yunnan and Guizhou provinces in china,and have only small and sparsely distributed populations with limited individual numbers.It explained that the Quaternary Ice Age may have had a significant impact to the evolutionary history.We surveyed sequence variation of the chloroplast DNA (cpDNA) noncoding fragment rpl20-rps18 intergenic spacer and trnV intron throughout the range of Dipteronia Oliv.twenty haplotypes were detected by analyzing 18 populations of this species. Sequence length varied from 995 by to 1017bp.Base composition was with high A+Tcontent of 66.1%.Relatively high level of haplotype diversity (h=0.716) and nucleotide diversity (Pi=0.007) were detected in D. sinensis Oliv..An analysis of molecular variance (AMOVA) for populations of M. striata showed that the genetic varia-tion mainly resided among populations (82.88%), and the estimates of interpopulation differentiation were very high (GST=0.499, FST=0.83, NST=0.802). Further, a significant phylogeographic structure was present (NST＞GST,P＜0.05).Mantel test indicated that the genetic distance between populations and geographic distance were positively correlated (r=-0.5716, p= 0.01).Tajima's D(-0.92628) and Fu and Li's D*(-4.21060) are negative,but not significantly(P＞0.10).According to the geographical distribution of cpDNA haplotype speculated that the Sichuan Basin or Qin-Ba mountain or Shennongjia Mountains served as a possible refugium during the Quaternary glaciations.We postulated that the genus Dipteronia Oliv. is not a large-scale migration and diffusion at the end of ice age.The results of nested clade analysis showed the interglacial or post-glacial range expansion by plants from the refugium followed by allopatric and past fragmentation shaped the present distribution patterns of haplotypes. Another reason is that restricted gene flow with isolation by distance.