生态分化选择对沙米(Agriophyllum squarrosum)表型多样性的影响

The Influence of Selection of Ecological Differentiation to the Phenotype Polymorphism of Agriophyllum squarrosum

沙米(Agriophyllum squarrosum),又名沙蓬,是广布于中国温带沙漠流动沙丘、半流动沙丘或河岸沙地的固沙先锋植物,具有重要的生态农业价值,也是研究适应性进化的理想材料。为了探讨沙米适应沙漠环境异质性的遗传基础,通过同质园实验,比较分析了采自分布区南部和北部的16个群体的沙米个体的数量性状表型分化、基于ITS序列变异的遗传分化及基于worldclim环境异质性之间的关系。结果发现:与北部群组相比,南部群组表型性状内部差异大,多样性高;通过数量性状差异(QST)与分子遗传差异(FST)组间和组内比较发现,组间和南部群组组内的FST值均高于QST值,表明群体处于稳定的一致选择之中;而北部群组组内QST值均大于FST值,表明存在明显的地方适应性,群体间个体的混合存在远交衰退的风险,因而可以将南部群体移植到北部群体来进行沙米群体的遗传复壮。此外,在南北群组间种子大小和基部枝长的QST值均高于环境异质性分化,说明该表型的本地适应性不能完全被基于温度和降雨量的环境异质性所解释。通过对风力大小与性状的相关性分析发现,冬季最大风速显著影响沙米种子大小,而基部枝长则与7、8月最大风速正相关,说明沙米的表型分化是适应不同风沙环境的结果。这一研究不仅探索出一种评估野生资源对气候变化适应潜力的新方法,同时可为理解潜在粮食作物沙米的表型结构对气候变化的响应提供重要数据,并为野生资源植物的生态适应性遗传机理研究提供范例。

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 FST were much higher than that of QST within the south group and among all populations,suggesting an unifying selection were acting in these populations.However,QST was found to be higher than FSTin 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 QSTon 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.