危害松树的小蠹虫与其伴生菌的相互关系

危害健康松属植物的小蠹虫经常与一些特殊的真菌相联系。在小蠹虫危害松属植物的过程中,这些真菌被小蠹虫的一些特殊结构或者体表携带到松属植物上。小蠹虫与其伴生菌的联系表明小蠹虫和其伴生菌之间是一种互惠互利的关系。伴生菌随小蠹虫扩散而被带到新的寄主树木。而伴生菌或作为小蠹虫的食物来源,但更重要的是,有些伴生菌能够通过其菌丝渗透寄主组织,释放毒素,致死寄主树木,以帮助小蠹虫降低寄主抗性。许多研究致力于探索小蠹虫/伴生菌联合体与寄主树木之间关系的特征和确定小蠹虫与其伴生菌相互关系在生态学上的意义。然而,不同小蠹虫和其伴生菌所组成的共生体系,不同小蠹虫的种群数量,和不同环境条件下同种小蠹虫与其伴生菌相互作用方式的差异使我们在研究小蠹虫和其伴生菌这个共生体系时,对它们各自在成功聚集寄主树木过程中所发挥的重要作用的概括变得非常困难。     

落叶松八齿小蠹与长喙壳真菌间的种特异性伴生关系

小蠹虫与长喙壳类真菌(Ophiostomatoid fungi)在自然界中形成稳定的伴生关系,是森林生态系统内一种普遍的生态学现象。已有研究表明欧亚大陆的齿小蠹属(Ips)昆虫与多种长喙壳类真菌形成广泛的伴生关系,其中部分真菌是重要的针叶树病原菌。随着借助于DNA信息特征的系统发育分析,揭示出形态特征和亲缘关系十分接近的3种齿小蠹属昆虫,云杉八齿小蠹(I.typographus),欧洲落叶松八齿小蠹(I.cembrae)和亚洲落叶松八齿小蠹(I.subelongatus)确定为不同种之后,相应地与之稳定伴生的长喙壳类真菌Ceratocystis polonica也由过去一个种揭示为3个种的复合体,各自与3种小蠹虫稳定伴生,形成密切的种特异性伴生关系。小蠹虫与真菌的种特异性伴生被认为是处于同一森林生态系统内的生物协同进化的结果。通过对我国东北地区落叶松八齿小蠹虫体、坑道标本上伴生真菌菌株的采集、分离和生理学、形态学特征观察,以及基于ITS、β-tubulin、MAT-2 HMG box多位点DNA序列的系统发育分析,首次确定了长喙壳真菌Ceratocystis fujiensis在我国东北地区异域分布的3种落叶松林内普遍存在,与落叶松八齿小蠹形成稳定的伴生关系。作为亚洲落叶松八齿小蠹伴生的主要真菌,也是伴生菌区系中的先锋种和致病力最强的病原菌,C.fujiensis在我国落叶松人工林的广泛分布值得高度重视,将为制定防治病虫复合危害的有效策略和措施提供科学基础。研究结果进一步支持了齿小蠹属昆虫与长喙壳真菌间的种特异性伴生假说。同时,多基因序列特征表明落叶松八齿小蠹与C.fujiensis在亚洲范围内的不同地理种群存在着显著的遗传多样性,预示特异性伴生在不同种群间发生的可能,可以为种特异性伴生假说和小蠹虫-真菌间共生关系的研究提供良好的模式材料。     

小蠹虫对针叶类寄主树木的选择危害机制

小蠹虫对寄主植物的选择是一个非常复杂的过程,也是近年来小蠹虫生态学研究的一个热门话题。文章对国内外小蠹虫寄主搜寻、寄主识别,以及适宜寄主选择等机制等方面的最新研究成果进行了系统报道。     

小蠹虫类异戊二烯类聚集信息素的生物合成

小蠹虫(小蠹科)是重要的森林蛀干害虫,在蛀食坑道时导致树木水分和养分运输系统受到破坏,短时间内对整片森林造成严重的经济危害。聚集信息素在小蠹虫聚集危害过程中扮演着非常重要的角色,目前已有多种小蠹虫聚集信息素成分被鉴定并成功应用于生产防控工作中。类异戊二烯类聚集信息素是小蠹虫中极为重要的一类聚集信息素,其主要成分包括小蠹烯醇、小蠹二烯醇、马鞭草烯醇及其衍生物。本文从类异戊二烯类聚集信息素的生物合成前体物质、生物合成位点、生物合成途径、取食和JHШ调控、微生物与其生物合成关系以及展望6个方面出发,全面阐述了齿小蠹属Ips和大小蠹属Dendroctonus中小蠹虫聚集信息素的生物合成机制及调控机制。文中首先重点阐述了小蠹虫体内以甲羟戊酸途径从头合成小蠹二烯醇以及利用寄主成分α-蒎烯直接合成马鞭草烯醇的生物合成过程;其次阐述了生物合成途径中关键酶和基因对小蠹取食和JHШ处理的响应以及小蠹虫肠道微生物和伴生真菌对该类聚集信息素生物合成的影响;最后,针对小蠹虫类异戊二烯类聚集信息素生物合成研究作了探讨和展望。本文为开发和应用其聚集信息素控制小蠹虫危害提供理论基础。     

华山松大小蠹及其伴生蓝变真菌对华山松木质部危害的解剖学特征

为揭示华山松大小蠹和伴生蓝变真菌引起秦岭华山松枯萎的机制,选择秦岭北坡沣峪林场境35年树龄的健康华山松Pinus armandi为研究对象,对接种华山松大小蠹Dendroctonus armandi及与其伴生的蓝变真菌Ceratocystis polonica引起的寄主树木木质部形态变化进行了解剖观察。结果表明：接种致病性蓝变真菌C. polonica 1周后的4株华山松 的木质部组织内,蓝变区域显著增加,4～6周后蓝变区域不再增加; 而在接种无菌琼脂的2株对照华山松的木质部组织内,没有检测到蓝变区域。研究结果提示蓝变真菌C. polonica是致死秦岭华山松的重要病原菌,该伴生菌随华山松大小蠹入侵健康寄主华山松木质部组织,在木质部定居并分解木质部,堵塞树脂道,致使寄主华山松树脂代谢和水分代谢紊乱。该研究结果表明,虽然华山松大小蠹长期以来被认为是致死华山松的毁灭性小蠹虫,但是其共生蓝变真菌C. polonica对成熟华山松的致害作用不应该被忽视。     

小蠹虫人工饲养方法简介

<正> 小蠹虫是重要的森林和检疫害虫之一。其体小,生活隐蔽,繁殖迅速,危害初期很难被人们发现,一旦暴发成灾很难防治,能毁坏大片森林。故我们应加强小蠹虫基本生物学的研究。小蠹虫的人工饲养是研究其生活史、生物学习性、种间和种内的通讯联系、种群的模拟预测模     

小圆胸小蠹及其虫菌共生体研究进展

小圆胸小蠹是蛀干为害的食菌小蠹,与其伴生菌构成虫菌共生体,称方胸小蠹—镰孢菌共生体,造成寄主机械损伤、枝干枯死和木材腐烂。在全球范围内寄主达63科342种,对果树、森林及城市景观等造成严重威胁,被国家林业局定为国际重大林木害虫。国外最新的分子学研究显示,方胸小蠹—镰孢菌共生体以种团形式出现,由至少5个形态上无法区分的小蠹种及其伴生菌构成,每一个小蠹种携带1或2种镰孢菌。该种团中的某些种及其伴生菌已经成为入侵物种,攻击并感染健康树木,造成了严重威胁。综述了该种团的生物学及生态学、伴生菌及寄主选择研究进展,以及食菌小蠹的控制途径,指出了我国有分布的该种分类地位急需确定,我国云南分布的该小蠹可能对我国更多地区城市阔叶树种构成威胁,对针叶树也可能构成潜在威胁。当前迫切需要在通过分子学手段澄清其分类地位基础上,深入开展种群生物学及生态学研究,以及伴生菌及寄主选择研究,揭示其成灾机制,为其有效控制提供技术支撑,以遏制其扩散蔓延的势头。     

松树蜂与其共生真菌的互利共生关系

松树蜂Sirex noctilio Fabricius是一种重要的国际林业检疫性害虫,主要危害针叶树,原产欧亚大陆和北非。近100多年来,先后入侵大洋洲(新西兰和澳大利亚)、南美洲(乌拉圭、阿根廷、巴西和智利)、北美洲(加拿大和美国),以及南非。2013年8月,在中国黑龙江省内首次发现松树蜂,目前发现其主要危害樟子松。松树蜂能与一种淀粉韧革菌属Amylostereum的真菌Amylostereum areolatum(Fr.)Boidin形成严格的互利共生关系,该虫除直接钻蛀树木外,还能通过产卵行为将自身毒素腺体分泌的毒素和体内共生真菌随同虫卵一起注入寄主树木体内,形成"虫-毒-菌"3个致害因子相互协作的特殊危害方式,加速树势的衰弱并造成寄主树木死亡。本文就国内外松树蜂与其共生菌互利共生关系的研究进行了综述,分别从结构与功能的层次上对其互利共生关系进行了梳理和总结,重点阐释了松树蜂与共生菌的营养共生关系,松树蜂携带传播共生菌的机制,共生菌的种群遗传学以及松树蜂毒素和共生菌在危害寄主树木时的协同关系等。以期为开展关于松树蜂的专项研究提供一些合理的建议,同时为积极有效地防控该害虫提供科学依据。     

纵坑切梢小蠹对云南松蛀害研究

在昆明地区,纵坑切梢小蠹Tomicus piniperda L.表现出枝梢聚集、树干蛀害等重要的行为学特征,形成三种基本蛀害模式。横坑切梢小蠹、蓝色伴生真菌参与了纵坑切梢小蠹危害过程,并在其中发挥积极作用。上述因素的综合影响,加强了纵坑切梢小蠹对云南松Pinus yunnanensis寄主树木的危害能力。     

纵坑切梢小蠹对云南松蛀害研究

在昆明地区,纵坑切梢小蠹Tomicus piniperda L.表现出枝梢聚集、树干蛀害等重要的行为学特征,形成三种基本蛀害模式。横坑切梢小蠹、蓝色伴生真菌参与了纵坑切梢小蠹危害过程,并在其中发挥积极作用。上述因素的综合影响,加强了纵坑切梢小蠹对云南松Pinus yunnanensis寄主树木的危害能力。     

On the origin of the Hirudinea and the demise of the Oligochaeta

The phylogenetic relationships of the Clitellata were investigated with a data set of published and new complete 18S rRNA gene sequences of 51 species representing 41 families. Sequences were aligned on the basis of a secondary structure model and analysed with maximum parsimony and maximum likelihood. In contrast to the latter method, parsimony did not recover the monophyly of Clitellata. However, a close scrutiny of the data suggested a spurious attraction between some polychaetes and clitellates. As a rule, molecular trees are closely aligned with morphology-based phylogenies. Acanthobdellida and Euhirudinea were reconciled in their traditional Hirudinea clade and were included in the Oligochaeta with the Branchiobdellida via the Lumbriculidae as a possible link between the two assemblages. While the 18S gene yielded a meaningful historical signal for determining relationships within clitellates, the exact position of Hirudinea and Branchiobdellida within oligochaetes remained unresolved. The lack of phylogenetic signal is interpreted as evidence for a rapid radiation of these taxa. The placement of Clitellata within the Polychaeta remained unresolved. The biological reality of polytomies within annelids is suggested and supports the hypothesis of an extremely ancient radiation of polychaetes and emergence of clitellates.     

On the ontogeny of the haptor and the evolution of the Monogenea

Data on the ontogeny of the posterior haptor of monogeneans were obtained from more than 150 publications and summarised. These data were plotted into diagrams showing evolutionary capacity levels based on the theory of a progressive evolution of marginal hooks, anchors and other attachment components of the posterior haptor in the Monogenea (Malmberg, 1986). 5 + 5 unhinged marginal hooks are assumed to be the most primitive monogenean haptoral condition. Thus the diagrams were founded on a 5 + 5 unhinged marginal hook evolutionary capacity level, and the evolutionary capacity levels of anchors and other haptoral attachement components were arranged according to haptoral ontogenetical sequences. In the final plotting diagram data on hosts, type of spermatozoa, oncomiracidial ciliation, sensilla pattern and protonephridial systems were also included. In this way a number of correlations were revealed. Thus, for example, the number of 5 + 5 marginal hooks correlates with the most primitive monogenean type of spermatozoon and with few sensillae, many ciliated cells and a simple protonephridial system in the oncomiracidium. On the basis of the reviewed data it is concluded that the ancient monogeneans with 5 + 5 unhinged marginal hooks were divided into two main lines, one retaining unhinged marginal hooks and the other evolving hinged marginal hooks. Both main lines have recent representatives at different marginal hook evolutionary capacity levels, i.e. monogeneans retaining a haptor with only marginal hooks. For the main line with hinged marginal hooks the name Articulon-choinea n. subclass is proposed. Members with 8 + 8 hinged marginal hooks only are here called Proanchorea n. superord. Monogeneans with unhinged marginal hooks only are here called Ananchorea n. superord. and three new families are erected for its recent members: Anonchohapteridae n. fam., Acolpentronidae n. fam. and Anacanthoridae n. fam. (with 7 + 7, 8 + 8 and 9 + 9 unhinged marginal hooks, respectively). Except for the families of Articulonchoinea (e.g. Acanthocotylidae, Gyrodactylidae, Tetraonchoididae) Bychowsky's (1957) division of the Monogenea into the Oligonchoinea and Polyonchoinea fits the proposed scheme, i.e. monogeneans with unhinged marginal hooks form one old group, the Oligonchoinea, which have 5 + 5 unhinged marginal hooks, and the other group form the Polyonchoinea, which (with the exception of the Hexabothriidae) has a greater number (7 + 7, 8 + 8 or 9 + 9) of unhinged marginal hooks. It is proposed that both these names, Oligonchoinea (sensu mihi) and Polyonchoinea (sensu mihi), will be retained on one side and Articulonchoinea placed on the other side, which reflects the early monogenean evolution. Except for the members of Ananchorea [Polyonchoinea], all members of the Oligonchoinea and Polyonchoinea have anchors, which imply that they are further evolved, i.e. have passed the 5 + 5 marginal hook evolutionary capacity level (Malmberg, 1986). There are two main types of anchors in the Monogenea: haptoral anchors, with anlages appearing in the haptor, and peduncular anchors, with anlages in the peduncle. There are two types of haptoral anchors: peripheral haptoral anchors, ontogenetically the oldest, and central haptoral anchors. Peduncular anchors, in turn, are ontogenetically younger than peripheral haptoral anchors. There may be two pairs of peduncular anchors: medial peduncular anchors, ontogentically the oldest, and lateral peduncular anchors. Only peduncular (not haptoral) anchors have anchor bars. Monogeneans with haptoral anchors are here called Mediohaptanchorea n. superord. and Laterohaptanchorea n. superord. or haptanchoreans. All oligonchoineans and the oldest polyonchoineans are haptanchoreans. Certain members of Calceostomatidae [Polyonchoinea] are the only monogeneans with both (peripheral) haptoral and peduncular anchors (one pair). These monogeneans are here called Mixanchorea n. superord. Polyonchoineans with peduncular anchors and unhinged marginal hooks are here called the Pedunculanchorea n. superord. The most primitive pedunculanchoreans have only one pair of peduncular anchors with an anchor bar, while the most advanced have both medial and lateral peduncular anchors; each pair having an anchor bar. Certain families of the Articulonchoinea, the Anchorea n. superord., also have peduncular anchors (parallel evolution): only one family, the Sundanonchidae n. fam., has both medial and lateral peduncular anchors, each anchor pair with an anchor bar. Evolutionary lines from different monogenean evolutionary capacity levels are discussed and a new system of classification for the Monogenea is proposed.In agreeing to publish this article, I recognise that its contents are controversial and contrary to generally accepted views on monogenean systematics and evolution. I have anticipated a reaction to the article by inviting senior workers in the field to comment upon it: their views will be reported in a future issue of this journal. EditorIn agreeing to publish this article, I recognise that its contents are controversial and contrary to generally accepted views on monogenean systematics and evolution. I have anticipated a reaction to the article by inviting senior workers in the field to comment upon it: their views will be reported in a future issue of this journal. Editor