基于叶绿体16S rRNA的绿色裸藻类系统发育及性状进化研究

该研究基于叶绿体16S rRNA基因序列，构建绿色裸藻类的系统发育树，并对绿色裸藻类植物8个形态性状进行祖先重建分析，以明确绿色裸藻类植物的系统演化关系，为研究该类植物的起源提供理论依据。结果表明：(1)贝叶斯法构建的绿色裸藻类系统发育树显示，双鞭藻属与拟双鞭藻属互为姐妹群，扁裸藻属、鳞孔藻属和盘裸藻属亲缘关系较近，而囊裸藻属和陀螺藻属亲缘关系较近，裸藻属、隐裸藻属、柄裸藻属和旋形藻属亲缘关系较近，表明裸藻属不是一个单系类群。(2)基于形态性状的祖先重建结果显示，绿色裸藻类相对原始的7个性状包括：表质柔软易变形，出现螺旋形线纹，细胞后端渐尖或尖尾刺状，无囊壳，叶绿体为片状、盾状或大盘状，具无鞘蛋白核，副淀粉粒为小颗粒状且数量不定，而鞭毛长度不能推断可能的祖先状态。(3)综合8种性状祖先重建结果发现，裸藻属和眼裸藻属植物具有所有原始性状，可能是最先出现的绿色裸藻类的祖先。

Phylogenetic and Morphological Evolution of Green Euglenophytes Based on 16S rRNA in Chloroplasts

Based on the 16S rRNA gene sequence of chloroplasts, this study constructed the phylogenetic tree of green euglenophyte and reconstructed their ancestor on the base of 8 morphological characters, which will clarify the phylogenetic relationships of green euglenophyte and provide theoretical basis for the study of the origin of these plants. The results indicated: (1) the phylogenetic tree of green euglenophyte constructed by Bayesian showed that Eutreptia and Eutreptiella are sister groups, and Phacus, Lepocinclis and Discoplastis are close relatives. We also can see that Trachelomonas and Strombomonas are close relatives, and Euglena, Cryptoglena, Colacium and Monomorphina have close genetic relationships. It is showed that Euglena is not a monophyletic group. (2) The results of ancestral reconstruction based on morphological characters showed that 7 relatively original characters of green euglenophyte included: cuticula soft and easy deformation, spirally striated, posterior end slightly narrowing or sharp elongated cauda, without lorica, chloroplasts show sheet, shield, or plate, pyrenoid without sheath, with many small grains are primitive traits, but the length of flagella can not infer possible ancestral states. (3) The results of ancestral reconstruction based on 8 morphological characters showed that Euglena and Euglenaria which have original characters may be the ancestor of green euglenophytes who appear earliest.