多基因联合分析棒束孢属Isaria(Ascomycota,Cordycipitaceae)系统发育关系

Multilocus phylogenetic analyses of the genus Isaria(Ascomycota, Cordycipitaceae)

对棒束孢属Isaria及近缘属物种开展5基因(nr SSU、nr LSU、tef-1α、rpb1和rpb2)测序并联合分析,结合Gen Bank相关类群序列,探讨棒束孢属系统发育关系,最终获得95个菌株、58个明确分类群的2–5基因序列。利用MEGA和Mr Bayes软件进行多基因聚类分析,结果表明棒束孢属多系起源于虫草菌科中,分3个不同分支。A支主要由Isaria cicadae、I.teniupes、I.coleopterorum、I.fumosorosea和I.cateniannulata等组成;B支包括I.poprawkii、I.locustica、I.javanica、I.amoenerosea和I.cateniobliqua;C支仅有I.farinosa。分支间被Cordyceps militaris、C.ninchukispora、C.pruinosa等隔开。棒束孢在形态上,主要以瓶梗基部膨大、尖端变细及孢子呈链状等特征与其他类群分开,但同时也发现有棒状分生孢子梗和单孢子类型。基于节点的分歧时间预测分析,推测棒束孢属首次分化于70Mya,但棒束孢属主要物种形成却在60–55Mya,且3个分支的棒束孢物种为快速同时形成,而后大多数类群表现遗传稳定。同时发现,与Isaria Clade A较近一支有粉被玛利亚霉Mariannaea pruinosa(C.pruinosa无性型)和蛹草蚧霉Lecanicillium militaris(C.militaris无性型);与粉棒束孢距离最近一支有Akanthomyces aculeatus(C.tuberculata无性型)和L.attenuatum(C.confragosa无性型),是两个不同的属征分类群,且相互间遗传距离较近。根据棒束孢属及其近缘种属形态特征的复杂性推测,棒束孢属在快速物种形成中,其近缘类群存在一定程度的丢失和选择性演化。

In order to explore the systematic relationships of the genus Isaria, 5 genes（nr SSU, nr LSU, tef-1α, rpb1 and rpb2） were sequenced and the conjoint analyses were carried out for the species of Isaria and its relatives. Combined the related groups in Gen Bank, a total of 95 gene datasets were obtained from 58 species with 2–5 genes each. The multi-gene cluster was conducted by using the MEGA and Mr Bayes softwares. The results showed that Isaria spp. could be divided into 3 groups, i.e., clade A, B and C, with not being monophyletic in the family Cordycipitaceae. The clade A contained Isaria cicadae, I. teniupes, I. coleopterorum, I. fumosorosea and I. cateniannulata. The clade B mainly included I. poprawkii, I. locustica, I. javanica, I. amoenerosea and I. cateniobliqua. Only I. farinosa was filled in the clade C. The 3 groups were partitioned by the species Cordyceps militaris, C. ninchukispora, C. pruinosa etc. The genus Isaria was distinguished from others genera by the characteristics of conidiogenous cell phialophore, consisting of a cylindrical or swollen basal portion, tapering or abrupt into a long distinct neck, and of the chain form of conidium. According to the divergence time based on the distinguished node, it was suggested that Isaria spp. would be firstly diverged 70 Mya. While the speciation of Isaria should occur in 60–55Mya. An interesting result was the species formations of the 3 clades in Isaria were quick and simultaneous during this period, and then the genetic stability was kept in most groups. Meanwhile, Mariannaea pruinosa（anamorph of C. pruinosa） and Lecanicillium militaris（anamorph of C. militaris） were closed to the species of Isaria Clade A. Akanthomyces aculeatus（anamorph of C. tuberculata） and L. attenuatum（anamorph of C. confragosa） had close relationships with I. farinosa, while these species were obviously different in traditional classifications. Morphological characteristics were complex in Isaria and its relatives. Thus it is suggested there seems to be some degree of loss and selective adaptive evolution during the quick and simultaneous speciation of the species in the genus.