腐质霉属及其近似属嗜热丝孢菌属的分类及分子系统学研究

The fungi of Humicola and Thermomyces genera have important economic and ecological value. For a long time, because conidiophores are very short or lack with most species in two genera, the taxonomic criteria of both genera mainly were based on the size and morphological characteristics of conidia. Thus, the delimitation factors between these two genus were ambiguous, and similarity was obvious. There was a great divarication for whether Thermomyces was one synonym of Humicola. The taxonomic confusion on the level of generic and species level was caused by the morphological species could not be delimited clearly and the delimitation criteria of species which were variable and easily affected by environment and cultural condition. Meanwhile, traditionally taxonomy of this fungal group based on morphology was not enough to reflect the evolutionary relationship and was very difficult to identify some ambiguous taxa. This project draws up to use the sequences of three DNA markers (rDNA ITS, EF1а、RPB2) to construct phylogenetic trees and to analyze the phylogenetic relationship of these two genera and species. Hopefully the new taxonomic system and evolutionary relationship suitable for this fungal group were rebuilt by combining the morphology, ecology and phylogeny. Some ambiguous taxa or related species were re-identified. The results will provide the support for systematically developing the taxonomic research of other fungal groups in hyphomycetes.

腐质霉属与嗜热丝孢菌属真菌具重要的经济学及生态学意义。长期以来，由于两属多数种分生孢子梗很短或缺，两属的分类都主要依据侧生厚垣孢子的大小和形态，两属间界定因子不清晰，相似性明显，后者是否为前者的异名属存在很大分歧，用于种间界定的特征都是多变而连续的数量性状且易受环境或培养条件的影响，形态物种间界限不清晰，导致了属、种分类研究的混乱。另外，传统上该类群真菌的形态学划分依据不足反映属、种的系统发育关系，也难以作为一些疑难种的鉴定依据，本项目拟以模式标本或菌株为基础，采用rDNA ITS、EF1а、RPB2基因序列构建系统发育树，分析确定两属、种间系统发育关系，通过形态、生态等表型生物学特征与基因型特征相结合建立适宜该类群趋于自然的新分类系统和演化关系；并以此为依据对两属进行重新界定和划分，澄清部分疑难种或相似种的分类地位。该研究将为深入开展暗色丝孢真菌其它类群真菌的系统分类研究提供技术支持。

腐质霉属(Humicola)和嗜热丝孢菌属(Thermomyces) 两属在形态上相似，仅靠形态特征有时难以准确界定两属；在两属种内鉴定上，用于种间界定的因子少且不稳定，特别是腐质霉属，经过很长一段时间的积累，种的类别增多，该系统显现出混乱，形态物种间界限不清晰，属内疑难种或相似种分类地位存在较大争议；另外，两属真菌的形态学分类不足以反映它们的系统发育关系。基因数据运用正改变学者对微生物种、属以及更高水平的分类认知；从单基因片段的使用到多基因结合进化分析，对微生物的分类位置，有了较为准确的定位。本项目在单基因和多基因分子系统学的基础上，结合形态学研究探讨两属的分类学问题。首先，通过分别构建毛壳科(Chaetomiaceae)的ITS和LSU的单基因及ITS+LSU+TUB多基因系统发育树，讨论了传统的腐质霉属在毛壳科的分类地位及系统发育关系。结果发现：传统的腐质霉属应界定为两个属，其中一个属因包含模式菌株棕黑腐质霉变种主模式(Humicola fuscoatra var. fascoatra, Ex-type)，所以仍沿用腐质霉属(Humicola)作为属名，其有性型属推测为Farrowia；另一新属命名为新腐质霉属(Neohumicola gen. nov.)，其有性型属推测为Chaetomium。此外，基于ITS、LSU、β-tubulin、RPB2序列重建了腐殖霉属和新腐质霉属属内种间的单基因及多基因的系统发育树，探讨了该属部分种的遗传进化关系。结果：在腐质霉属(Humicola)中，共鉴定出8个种，分别为H. verruculosa、H. fuscoatra、H. irregularis、H. brachypodi、H. pedunclensis和3个未定种Humicola spp.（HSAUP1915、HSAUP0905、HSAUP1001），在新腐殖霉属(Neohumicola gen. nov.)中，共22株菌株，被鉴定为2个新组合种，即N. grisea var. grisea comb. nov.和N. jilongensis comb. nov.。最后，通过ITS序列分析及形态学研究，把4株嗜热丝孢菌属菌株鉴定为疏棉嗜热丝孢菌Thermomyces lanuginosus，并讨论了该属的分类地位。该项目为其它真菌分类单元的系统分类提供借鉴。