虫草属分子系统学研究现状

近年来的分子系统学研究结果表明 ,麦角菌目 (Clavicipitales)与肉座菌目 (Hypocreales)以及虫草属Cordyceps(Fr.)Link]与麦角菌科 (Clavicipitaceae)内的有关种属关系密切 ,但虫草属为一多系群 ,其中只有新虫草亚属的种类形成单系群。虫草属种类的进化与寄主有一定的关系 ,有关研究显示它们在亲缘关系相差很大的寄主之间多次转移。多个独立的ITS序列研究表明 ,阔孢虫草 (CordycepscrassisporaM .Zangetal.)、甘肃虫草(CordycepsgansuensisK .Y .Zhangetal.)、多轴虫草 (CordycepsmultiaxialisM .Zang&Kinjo)、尼泊尔虫草 (CordycepsnepalensisM .Zang&Kinjo)与冬虫夏草 Cordycepssinensis(Berk.)Sacc.]为同一物种 ;RAPD和ITS序列分析还显示不同地理分布的冬虫夏草存在明显的遗传分化。分子生物学方法在确定有性型与无性型的关系上已经为多种虫草菌提供了有力的证据。本文主要对虫草属分子系统学研究现状进行了综述 ,同时就分子生物学研究中的取样问题、一些分子方法的适用范围以及有性型与无性型的关系等问题进行了讨论。

Current Understanding of Molecular Systematics of Cordyceps

Recent development of molecular systematics of Cordyceps is reviewed.Phylogenetic studies have shown that Clavicipitaceae and other families of Hypocreales form a monophylogenetic group and that Cordyceps is closely related to other genera of Clavicipitaceae.Molecular research indicates that Cordyceps is a polyphyletic taxon with members of the genus forming several clades in rDNA sequence analyses.Among the subdivisions of the genus, only Cordyceps subgen.Neocordyceps appears to be monophyletic.A suggestion is that Cordyceps evolved in association with their hosts and that shifts between distantly related hosts occurred several times in the course of evolution.Type I intron in the large and small sub-unites of nuclear rDNA has been found in different lineages of Cordycpes species and the inserting positions of the intron are closely related to the phylogeny of Cordyceps hosts.Several independent DNA sequence analyses support C.crassispora, C.gansuensis, C.multiaxialis, C.nepalensis and C.sinensis to be the same species because they share similar ITS sequences.RAPD and ITS analyses reveal genetic variation among C.sinensis populations from different locations of the Tibetan Plateau.Molecular methods have provided firm evidence which establishes the connection between the anamorphic and teleomorphic states of Cordyceps.Beauveria brongniartii, B.sobolifera, Hirsutella sinensis, Metarhizium anisopliae var.majus, Mariannaea pruinosa and Paecilomyces hawkesii have been determined to be the anamorph of C.brongniartii, C.sobolifera, C.sinensis, C.brittlebankisoides, C.pruinosa and C.gunnii respectively.Sampling number and scope and the selection of samples have strong effects on the molecular results.Application of molecular markers in different research subjects and relationships between the anamorphs and teleomorphs are also discussed.