tudy on population genetic structure of Hypericum nagasawae Hayata

[[abstract]]Hypericum nagasawae Hayata and H. nokoense Ohwi are both endemic species in Taiwan. It is difficult to determine these two species since the closely morphological similarity between them. In this study, 4 chloroplast DNA non-coding regions, accD – psaI intergenic spacer, trnE – trnT IGS, rpl16 intron, and trnV – trnM (trnV intron included) IGS, were used to analyze their relationship. The results of molecular analysis are consistent with the taxonomic treatment of Robson (1996). Geographically, H. nagasawae is widely distributed in mountainous regions above 2,300 m in Taiwan, while H. nokoense is restrictively distributed in limestone regions in Shiu-Lin Township, Hualien. In order to uncover the population genetic structure of H. nagasawae, a total of 150 samples were collected from 10 populations, and two chloroplast DNA intergenic spacers, accD – psaI and trnE – trnT, were analyzed. 10 haplotypes were detected with 4 main haplotypes limitedly distributed in specific regions. Genetic differentiation among populations was generally high (mean FST = 0.744, Nm = 0.09). Both haplotypes in Mt Peitawu are endemic with the farthest genetic distance from other haplotypes. It suggested that the populations between Mt Peitawu and other regions have a long-term geographical isolation. The genetical distance and geographical distance (Isolation by distance test) have a moderate positive correlation when the population of Mt Peitawu was excluded. According to the result of Nested Clade Analysis, past fragmentation followed by range expansion had occurred. By integrating the present result and previous studies for other alpine plants, Northern Central Ridge was the genetic diversity center of alpine herbs of Taiwan. Glaciation might have played an important role contributed to the distribution pattern of haplotypes. According to neutral theory test (Tajima’s D, Fu & Li’s test) and BEAST software, however, last Glacial Age did not significantly influence population size.