2.1. Study site and plant material
Changbai Mountain is generally recognized as the highest peak in northeast China and eastern Eurasia, with obvious mountain climate characteristics. This environment is locally variable as small changes in altitude can lead to large changes in temperature, humidity, exposure, and other types of changes(X. Yang & Wu, 1998). The alpine region on Changbai Mountain is the southern boundary of alpine tundra in east Eurasia. The varied topography, weather, soil and other natural conditions have created rich biodiversity and vertical zonal distribution of vegetation on Changbai Mountain, which has more than 2,277 species of plants and a notable richness of endemic species.
From 2012 to 2014, fresh leaves were collected from 461 individuals belong to 36 nature populations of R. aureum along an environmental transect which altitude range from 1200m to 2600m a.s.l., annual mean temperature range from 0.1 °C to -6.6 °C and annual precipitation range from 761 mm to 1096 mm(Table 1, Figure C) . These populations were scattered along peaks of Changbai Mountain (32 populations), Laobai Mountain (2 populations), and Wangtian’e Mountain (2 populations)(Figure 1) . In each of the population, a random sample from 7 to 17 individuals was obtained. In each locality, individual samples were taken from plants separated by at least 5 m (in order to avoid sampling clones) and dried directly in silica gel for transport back to Jilin University for subsequent DNA extraction.
Table 1. Summary of AFLP variation for 36 populations of