Abstract:

Artemisia sphaerocephala is an extreme xerophytic subshrub and sand dominant species of northwest China. It has important sand binding properties and grows on drifting dunes, semi-drifting dunes and sometimes on fixed dunes in the steppe zone and desert zone. The current distribution range of A. sphaerocephala was investigated. The results show that it is distributed in central and western Inner Mongolia, northwestern Shanxi, northern Shaanxi, northern Ningxia, northern Qinghai, eastern Xinjiang, and Gansu in China and in southern Mongolia and is a Gobi- Mongolia distribution species. A new natural distribution site of A. sphaerocephala was discovered on the Otindag Sandy Land in central Inner Mongolia. The areal map of A. sphaerocephala has been drawn according to the specimens collected in different provinces and based on the literatures. Five populations of A. sphaerocephala were collected from main areas of their distribution and one population was collected from the new distribution site. The six populations were analyzed using random amplified polymorphic DNA (RAPD) markers. A total of 255 loci were obtained from 15 random primers, among which 232 loci were polymorphic. At the species level, the percentage of polymorphic loci was 91%. It showed that genetic polymorphism of A. sphaerocephala was high. The sequence of the percentage of polymorphic loci of the six populations was: Shapotou (SHPT) 83.4% >Yulin (YL) 75.3% >Azuoqi (AZQ) 74.1% >Wuhai fixed dune (WH2) 72.4%>Xilinhot (XLHT) 68.8%>Wuhai drifting dune (WH1) 66.7%. This sequence was slightly different from Shannon's diversity index. The latter was: SHPT>YL>AZQ>XLHT>WUH2>WUH1. The sequence of Nei's gene diversity was the same as the sequence for Shannon's diversity index. The genetic differentiation among populations (Gst) was 0.234 8 indicating that there was genetic differentiation among populations, but 76.52% of this variation existed within the populations. According to the results of cluster analysis based on Nei's genetic distances, correlations existed between genetic distances and geographical distances. However, for the Xilinhot population of Otindag Sandy Land and Yulin population of Mu Us Sandy Land, the geographical distances were far and genetic distances were close, indicating that there was a close connection between the populations on these two sandy lands of grassland regions. It is highly likely that A. sphaerocephala of Otindag Sandy Land came from Mu Us Sandy Land.