Molecular phylogeny and Cytogenetics with reference to the origin of Schsitosoma japonicum

为了验证Davis(1980,1992)提出的日本血吸虫非洲起源说，本研究对日本血吸虫的DNA序列、线粒体DNA基因排列和染色体定位进行了分析。到目前为止，我们的研究得出了亚洲起源理论的结论。不过，目前还不确定他们何时以及如何“走出亚洲”的表现。从我们的研究还表明，一些成员从非洲重新引入到亚洲，但目前还不清楚重新迁徙的方式和时间。本研究从种内变异的角度，研究了印度链霉菌群体中线粒体DNA CO1区单倍型的频率和地理分布。在孟加拉的Sindale中发现了两种不同的单倍型，它们的序列有很大的差异。来自孟加拉国的一只与来自马来西亚和斯里兰卡的S.Sindale形成了一个集群。另一个来自…孟加拉的More M与来自泰国的S.Sindale形成了一个集群。两个单倍型之间的DNA序列差异与独立物种之间的差异相一致。此外，还首次利用鼻血吸虫、南方血吸虫和牛血吸虫对血吸虫线粒体DNA基因排列中的热点区域(ND4-ND1)进行了分析。结果表明，这3个来自亚洲和非洲的物种都是非洲类型。为了确定南方链霉菌的分类地位，还利用每个区域的DNA序列以及包括ND4-ND1区和CO1区的三个区的串联序列进行了系统发育分析。前者表现出较不稳定的类群，而后者表现出稳定一致的类群，特别是在属间和种间的系统发育关系上。在这些调查中发现，隐名沙门氏菌最早从非洲群和印度沙门氏菌群的共同祖先物种分化而来。因此，这一结果否认了隐名血吸虫是从日本血吸虫群体的共同祖先分化而来的观点。较少

In this study, analyses for DNA sequences, mitochondrial (mt) DNA gene arrangements and chromosome mapping were carried out in order to verify the African origin theory of Schistosoma japonicum by Davis (1980, 1992). Our research to date reached the conclusion of the Asia origin theory, on the contrary. However, it is yet uncertain when and how 'Out of Asia' was possible for them to perform. It was also suggested from our studies that some members of the S. indicum group reintroduced from Africa to Asia, but it is also yet unknown about the rout and time of remigration. In this study, from the viewpoint of intra-specific variations, frequencies and geographic distributions of haplotypes in the CO1 region of the mt DNA were investigated in the S. indicum group. Two different haplotypes, that considerably differ from each other in sequence, were found in S. sindale from Bangladesh. The one from Bangladesh formed a cluster with that of S. sindale from Malaysia and Sri Lanka. The other fro … More m Bangladesh formed a cluster with that of S. sindale from Thailand. The difference in the DNA sequence between the two haplotypes corresponds with that between independent species. In addition, one of the hot regions (ND4-ND1) in the mt DNA gene arrangement of Schistosoma was analyzed for the first time using S. nasale, S. incognitum and S. bovis. As a result, it was clarified that these 3 species from Asia and Africa all turned out to be of the African type. A phylogenetic analysis using DNA sequences from each region as well as concatenated sequences including the three regions in the ND4-ND1 region plus the CO1 region was also carried out in order to confirm the taxonomical position of S. incognitum. The former analysis showed a rather unstable trees, but the latter revealed stable and congruent trees especially in terms of phylogenetic relationships between genera as well as species. Under these investigations, it was discovered that S. incognitum diverged earliest from the common ancestral species of the African group and the S. indicum group. Therefore, the result denies the idea that S. incognitum diverged from a common ancestor of the S. japonicum group. Less