Redecker D, Morton J B, Bruns T D
Department of Plant and Microbial Biology, University of California, 111 Koshland Hall, Berkeley, California 94720, USA.
Mol Phylogenet Evol. 2000 Feb;14(2):276-84. doi: 10.1006/mpev.1999.0713.
Using new and existing 18S rRNA sequence data, we show that at least five species of glomalean fungi lie outside the previously defined families and diverged very early in the evolution of that group. These five fungi would have been missed by many previous ecological studies because their sequences are not well matched to available taxon-specific primers and they do not stain well with the standard reagents used for morphological analysis. Based upon spore morphology, these species are currently assigned to Glomus and Acaulospora, and two of the species are dimorphic, exhibiting spore stages of both genera. This suggests that dimorphic spores are the ancestral state for the order and that one or the other morphology was lost in various lineages. Our analyses also show that Geosiphon pyriforme, a symbiont with cyanobacteria, is not necessarily a sister group of the Glomales; instead, it may be derived from mycorrhizal ancestors.
利用新的和现有的18S rRNA序列数据，我们发现至少有五种球囊霉目真菌不属于先前定义的科，并且在该类群的进化过程中很早就已分化。许多先前的生态学研究可能会遗漏这五种真菌，因为它们的序列与现有的分类群特异性引物匹配不佳，并且它们在用形态学分析的标准试剂染色时效果不佳。基于孢子形态，这些物种目前被归入球囊霉属和无梗囊霉属，其中两个物种是双态的，呈现出两个属的孢子阶段。这表明双态孢子是该目的原始状态，并且在不同的谱系中，其中一种或另一种形态已经消失。我们的分析还表明，与蓝细菌共生的梨形地管菌不一定是球囊霉目的姐妹类群；相反，它可能起源于菌根祖先。
