小兴安岭代表性菌物系统进化初步研究

Preliminary Study on Phylogenetic of Representative Fungi in Xiaoxing'an Mountain

为探索小兴安岭菌物系统进化关系并验证可应用于该地菌物的分子钟校正时间标准,采集小兴安岭凉水国家级自然保护区代表性菌物25种,对ITS1、5.8S和ITS2 rDNA区域进行PCR扩增、测序。同源序列多重比对后分析序列特征。以核酸进化的最适模型构建最大似然树、最大简约树和邻接树,自展检验重复1 000次估计可靠性。根据分子钟推测菌物分化发生时间。25种ITS序列平均碱基组成为T=28.66%、C=24.11%、A=26.19%和G=21.03%,总体转换/颠换差R=1.274。Tajima检验支持最大似然树和邻接树的系统发育关系。对于长期进化而言,无ITS核苷酸序列以绝对恒定的速率变化,分子钟不具有通用性。构建不受分子钟约束的最大似然树,根据枝长估计红毛盘菌与其他菌物分化发生在500 Ma,灰光柄菇与其他菌物分化发生在约130 Ma,多孔菌在内的其他菌物起源于约100～120 Ma。

In order to probe into the evolutionary relationship of fungi in Xiaoxing＇an mountain and verify the fungi phylogenetic molecular clock that can be applied to the area, 25 fungi rDNA series （ITS1, 5.8s and ITS2） were taken to conduct PCR amplifica- tion and sequence testing. Maximum likelihood tree, maximum parsimony tree and neighbor joining tree were constructed based on the most suitable model of nucleic acid evolution, and reliability was evaluated by repeating the test 1000 times. Timing of fungal evolu- tionary events was estimated by molecular clock. Average base composition of the 25 fungi were T = 28.66% , C = 24. 11% , A = 26. 19% and G =21.03%. The overall transition bias R was 1. 274. Taijima test is suitable for the phylogenetic relationship of likeli- hood tree and neighborhood tree. For long term evolution, the nucleotide without ITS changes with an absolute constant rate, and the likelihood ratio test significantly rejected the molecular clock of the ITS dataset of 25 sequences. The unclock maximum likelihood tree showed that Scutellinia scutellata split from the other fungi at about 500Ma, and the split of Pluteus atricapillus and others occurred at about 130Ma, the origin of Polyporales and other fungi were from 100 to 120 Ma.