基于rDNA ITS序列对绒泡菌目黏菌系统发育的探讨

A phylogenetic study of Physarida based on rDNA ITS sequence

绒泡菌目Physarida是黏菌纲Myxogastria最大的一个目,对其系统发育关系的研究一直是根据形态特征。为了从分子水平探讨绒泡菌目乃至黏菌纲的系统发育关系,以黏菌r DNA ITS通用引物对绒泡菌目5属8种黏菌的r DNA ITS进行扩增和测序,结合Gen Bank中已有的黏菌r DNA ITS序列,利用贝叶斯推断法(Bayesian inference,BI)和最大似然法(Maximum likelihood,ML)构建系统发育树。结果表明:绒泡菌目不同物种的r DNA ITS区在碱基组成和长度上差异明显,长度为777–1 445bp,G+C mol%在53.4%–61.9%之间。绒泡菌目与发网菌目Stemonitida聚类为两个明显的分支,在绒泡菌目分支上,绒泡菌科Physaraceae和钙皮菌科Didymiaceae各聚为一支,支持了形态学上以孢丝是否具有石灰质为依据区分这两个科的观点。由多份不同地理来源的鳞钙皮菌Didymium squamulosum材料组成的钙皮菌科又形成3个分支,证实了这个形态种是由地域来源广泛、繁殖亲和性各异和遗传变异较大的不同生物种组成的复合体。

Physarida is the biggest order in the class Myxogastria. The phylogenetic relationships in Physarida have been generally based on morphological characteristics. In order to study the phylogenetic relationships in Physarida and even in Myxogastria at the molecular level, the universal primers were used to amplify and sequence the rDNA ITS sequences from eight species representing five genera of the order Physarida. The obtained sequences were combined with known sequences in GenBank to construct a phylogenetic tree using both maximum likelihood （ML） and bayesian inference （BI） methods. The varieties for the rDNA ITS of different Physarida species were observed both on the base composition and length. The range of length are 777- 2 445bp, and G＋C mol% are between 53.4% and 62.9%. Physarida and Stemonitida are clustered into two distinct branches. On the branch of Physarida, Physaraceae and Didymiaceae were divided into two separate branches. The results supported taxonomic viewpoint making a distinction between the two families, based on capillitium with or without calcareous granulesDidymium squamulosum samples from different geographic regions are composed of three branches, confirming that this morphospecies is consist of a biological species complex with different geographical origins, reproductive incompatibility and genetic variation