中文摘要：

基于分支模型、位点模型及分支-位点模型对蕨类的rbcL基因所受到的选择压力进行了分析。结果显示：分支模型下检测到大部分分支处于负选择,仅4个分支处于正选择压力下,并且仅2分支具有统计上的显著性;在位点模型下,通过比较模型M1a/M2a和M7/M8,在氨基酸水平上模型M2a和模型M8均鉴定出98L位点被正选择;在模型M8下,鉴定负向选择位点共228个,占总序列的83.82%,从而揭示出负选择对rbcL基因的进化起着非常重要的作用;在分支位点-模型c下鉴定出262A被正选择。98L、262A位点分别位于rbcL羧基末端α/β桶结构域的第3和第8个α螺旋上。蕨类通过该结构域的适应性进化,适应白垩纪被子植物兴起而引发的陆地生态系统改变,研究结果为以后实验分析提供了首选位点。

英文摘要：

To understand the selective pressure acting on Rubisco and to examine possible differences in the evolutionary dynamics among ferns,we use branch model,site model and branch-site models established by Yang et al.to conduct the analyses.Except 4 branches,most of the branches are under purifying selection under branch model,and only 2 branches show statistics significance.Under the site model,based on the comparisons between the models M1a/M2a and M7/M8,98L was found to be positively selected under both model M2a and model M8;and under model M8,228 sites were identified as negatively selected,which consist of 83.82% of the gene.The results demonstrated that purifying selection has played a major role in the evolution of rbcL.The site 262A was further found to be a positively selected site under branch-site model c.98L,262A are in the α/β-barrel located on C-terminal domain of the large subunit of Rubisco.Through adaptive evolution of this domain,ferns responded to the terrestrial ecosystem changes initiated by the rise of angiosperms,and further experiments should pay more attention to these two sites.