以演化时间为新增指标构建真菌分类系统

随着分子系统发育研究的普及,真菌各分类类群逐渐被修订为单系发生类群,通常结合形态学特征为代表的表型特征（“单系+表型特征”）对不同的分类等级命名是最为普遍的方法。历史上存在的大量多系名称被逐步修订、补充和完善,各个不同等级类群的分类系统变得更加合理、客观和趋于自然,这是分类学进程中巨大的进步。然而系统发育重建所揭示的单系类群并没有相应的标准来对应于纲目科属等种上分类等级,所以并不能直接转换为分类系统,且在分类实践中,由于不同分类学家在决定各个单系类群对应的分类等级时采用的尺度不同、依据不一,严重影响分类系统的科学性和稳定性。随着分子钟分析方法的出现,实现了对现生生物类群演化时间的估算,所以在系统发育、表型特征研究的基础上,把演化时间作为真菌分类的新增指标来划分和命名种上分类等级的方法（“单系+表型特征+演化时间”）得以应用。本文回顾了首次利用这种方法重建蘑菇属分类系统的工作,目前研究所揭示的担子菌门和子囊菌门从门至科各分类等级的演化时间范围,及利用演化时间为新增指标在分类命名中的应用;分析了影响演化时间估算可靠性的关键因素及对策。我们认为在构建分类系统的研究中增加演化时间指标,使新分类系统体现类群进化过程中的时间维度,能更全面反映类群的进化历程,促进分类系统的科学性和稳定性。

Using divergence time as an additional criterion in fungal systematics

The flourish and popularity of molecular phylogenetic study greatly promoted the systematic study of fungi. Nowadays, naming taxa by “monophyly + phenotypes” is the most popular method applied in taxonomic studies, and the taxonomic systems of lots of historically problematic groups were thus revised, supplemented or reconstructed. Those more objective and natural systems for those monophyletic groups could be the greatest progress we have ever made in fungal taxonomy. However, a phylogenetic topology could not correspond to a taxonomic system as there do not have a universal criterion in ranking these monophyletic groups as genera, families, orders and classes (above species level), and that caused the unstable fungal taxonomic system. In practice, different taxonomists have different opinions in choosing criterion to rank taxa which greatly influenced the stability of fungal taxonomic system. With the advances of molecular clock analyses, estimation of divergence times of living taxa becomes available. Thus, based on phylogenetic and phenotypic studies, using divergence time as an additional criterion (“monophyly + phenotype + divergence time”) to rank higher-level taxa has been practiced. In this paper, the work which firstly rebuilt a standardized taxonomic system for the genus Agaricus by using divergence time as an additional criterion was reviewed, and the divergence time ranged from family to phylum in Ascomycota and Basidiomycota was revealed and the achievements of using divergence time as an additional criterion to rank taxa were enumerated. The key factors which influence divergence time estimation were discussed and corresponding suggestions were given. Generally, using divergence time as an additional criterion to build fungal taxonomic system can make the taxonomic system reflect the temporal dimension of evolution, and make the new system approach the evolutionary process and greatly promote the stability of related taxonomic system.