Abstract: Agriophyllum squarrosum, also called "sand rice", is a pioneer annual plant endemic to the mobile and semi-fixed sand dunes across the temperate deserts of China.It prevails important values in eco-agriculture and supports an ideal model for understanding the adaptive evolution. To investigate the genetic basis of how A. squarrosum adapt to the heterogeneous environment of deserts, in this paper, based on the common garden experiment with individuals sampled from northwest and northeast of China, we analyzed the relationships between/among the quantitative traits, the genetic differentiation based on the variety of nrITS and the heterogeneity of environment according to the worldclim. Our results showed that all the phenotypic traits were differentiated among the two groups, especially within the populations among the southern group. Comparison between the inter-and intra-groups showed that the values of F_ST were much higher than that of Q_ST within the south group and among all populations, suggesting an unifying selection were acting in these populations. However, Q_ST was found to be higher than F_ST in the north group, supported the local adaptation of the northern populations. This result indicated that these populations will be under a potential risk of outbreeding depression. Therefore, translocation of the southern genotypes into the north habitat will contribute to the genetic reinforcement of the northern populations. Furthermore, the values of Q_ST on the traits of seed diameter (SED) and basal branch length (BBL) were higher than that of environmental heterogeneity (Est) between the two groups, suggested that the climatic differentiation on the temperature and precipitation can not fully explain the phenotypic variation. Thus, we analyzed the relationships between wind speed and the phenotypic traits. Our data showed that the maximum wind speed in winter was strongly correlated with SED, while BBL was more affected by the maximum wind speed in July and August, which suggested that the blown sand environment plays an important role in shaping the adaptive phenotypic differentiation between groups in the desert plant species. In summary, this study not only provided a new evaluation method for adaptive potential in wild resources mitigating climate change, but also shed light on better understanding of the ecological genetic basis for how A. squarrosum adapted to the heterogeneous desert environment, which will further provide both the experienced data and theoretical basis for domestication of valuable desert plants.

Key words: Agriophyllum squarrosum, differentiation in quantitative traits, molecular genetic variation, environmental heterogeneity, wind, ecological selection