LoBuglio K F, Berbee M L, Taylor J W
Department of Plant Biology, University of California, Berkele 94720, USA.
Mol Phylogenet Evol. 1996 Oct;6(2):287-94. doi: 10.1006/mpev.1996.0077.
The phylogenetic relationship of the asexual mycorrhizal fungus Cenococcum geophilam Fr. among sexual ascomycetes was examined by phylogenetic analysis of nucleotide sequence data from the nuclear small subunit (18S) ribosomal RNA genie region. A specific focus of this study was to test the hypothesis that the genus Elaphomyces is the closest sexual relative of C. geophilum. Thus nucleotide sequence data of five C. geophilum isolates, three Elaphomyces species, and 44 additional genera of ascomycetes were included in the phylogenetic analyses. The percentage of similarity among the 18S rDNA sequences of the C. geophilum isolates examined was 99.8 to 100%, indicating that C. geophilum is monophyletic. Percent similarity of nucleotide sequence among the three Elaphomyces species was also high and ranged from 99.4 to 99.5%. DNA parsimony and distance analysis of the sequence data separated these 2 genera on distant clades when sequence from 44 additional genera of ascomycetes was included. Parsimony and distance analyses positioned C. geophilum as a basal, intermediate lineage between the two Loculoascomycete orders, the Pleosporales and the Dothidiales, and strongly supported Elaphomyces to be of Plectomycete origin. Among the sexual Ascomycetes examined, which included representative taxa from four classes of filamentous Ascomycetes (Plectomycetes, Pyrenomycetes, Discomycetes, and Loculoascomycetes), no close sexual relative to C. geophilum was identified. At least four independent lineages of mycorrhizal fungi were identified among the ascomycetes examined.
通过对来自核小亚基（18S）核糖体RNA基因区域的核苷酸序列数据进行系统发育分析，研究了无性菌根真菌地生团壳菌（Cenococcum geophilam Fr.）与有性子囊菌之间的系统发育关系。本研究的一个特定重点是检验以下假设：大团囊菌属（Elaphomyces）是地生团壳菌最亲近的有性亲缘属。因此，五个地生团壳菌分离株、三个大团囊菌物种以及另外44个有子囊菌属的核苷酸序列数据被纳入系统发育分析。所检测的地生团壳菌分离株的18S rDNA序列之间的相似性百分比为99.8%至100%，表明地生团壳菌是单系的。三个大团囊菌物种之间的核苷酸序列相似性百分比也很高，范围在99.4%至99.5%之间。当纳入另外44个有子囊菌属的序列时，对序列数据进行的DNA简约分析和距离分析将这两个属分隔在遥远的分支上。简约分析和距离分析将地生团壳菌定位为两个腔孢纲目（格孢腔菌目和座囊菌目）之间的一个基部中间谱系，并有力地支持大团囊菌起源于散囊菌纲。在所检测的有性子囊菌中，包括来自丝状子囊菌四个类（散囊菌纲、核菌纲、盘菌纲和腔孢纲）的代表性分类群，未发现与地生团壳菌有密切有性亲缘关系的类群。在所检测的子囊菌中至少鉴定出了四个独立的菌根真菌谱系。
