Cospeciation in the triplex symbiosis of termite gut protists (Pseudotrichonympha spp.), their hosts, and their bacterial endosymbionts
Cospeciation in the triplex symbiosis of termite gut protists (Pseudotrichonympha spp.), their hosts, and their bacterial endosymbionts
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DOI：
10.1111/j.1365-294x.2006.03219.x
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发表时间：
2007-03
影响因子：
4.9
通讯作者：
S. Noda;O. Kitade;T. Inoue;M. Kawai;M. Kanuka;K. Hiroshima;Yuichi Hongoh;R. Constantino;V. Uys
中科院分区：
文献类型：
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作者：
S. Noda;O. Kitade;T. Inoue;M. Kawai;M. Kanuka;K. Hiroshima;Yuichi Hongoh;R. Constantino;V. Uys
迄今为止，已经研究了两种生物体（即宿主和共生体或寄生虫）之间的许多共系统发育关系。然而，自然界中的有机体相互作用通常涉及多个成员。在这里，我们研究了三重共生系统的共生系统，该系统包含三种生物体的层次结构——鼻白蚁科的白蚁、这些白蚁肠道中的假毛线虫属的纤维素分解原生生物以及原生生物的细胞内细菌共生体。根据白蚁的两个线粒体基因和原生生物及其内共生体的核小亚基 rRNA 基因推断了分子系统发育，并对它们进行了比较。虽然肠道微生物通常被认为与宿主的联系比细胞内共生体的联系更松散，但假毛线虫原生生物与宿主白蚁几乎完全共分化，这可能是由于基于白蚁社会行为的直肠滋养或食粪的严格传播。除一例外，原生生物的内共生细菌在拟杆菌目中形成单系谱系，其分支模式与原生生物和白蚁的分支模式几乎相同。然而，一些非共同趋异的进化事件是明显的。这个三重共生系统的成员似乎在进化过程中已经协同存在，除了一些小例外。进化关系可能是由白蚁的社会性和肠道中复杂的微生物群落建立的。
A number of cophylogenetic relationships between two organisms namely a host and a symbiont or parasite have been studied to date; however, organismal interactions in nature usually involve multiple members. Here, we investigated the cospeciation of a triplex symbiotic system comprising a hierarchy of three organisms — termites of the family Rhinotermitidae, cellulolytic protists of the genus Pseudotrichonympha in the guts of these termites, and intracellular bacterial symbionts of the protists. The molecular phylogeny was inferred based on two mitochondrial genes for the termites and nuclear small‐subunit rRNA genes for the protists and their endosymbionts, and these were compared. Although intestinal microorganisms are generally considered to have looser associations with the host than intracellular symbionts, the Pseudotrichonympha protists showed almost complete codivergence with the host termites, probably due to strict transmissions by proctodeal trophallaxis or coprophagy based on the social behaviour of the termites. Except for one case, the endosymbiotic bacteria of the protists formed a monophyletic lineage in the order Bacteroidales, and the branching pattern was almost identical to those of the protists and the termites. However, some non‐codivergent evolutionary events were evident. The members of this triplex symbiotic system appear to have cospeciated during their evolution with minor exceptions; the evolutionary relationships were probably established by termite sociality and the complex microbial community in the gut.