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

为了验证Davis（1980,1992）提出的日本血吸虫的非洲起源理论，本研究进行了DNA序列分析、线粒体（mt） DNA基因排列和染色体定位。我们目前的研究得出的结论是亚洲起源说，与此相反。然而，目前还不确定他们何时以及如何在“离开亚洲”后表现出色。我们的研究还表明，籼稻群的一些成员从非洲被重新引入亚洲，但关于迁徙的路线和时间也尚不清楚。本研究从种内变异的角度，研究了籼稻组mt DNA CO1区单倍型的频率和地理分布。在孟加拉国的S. sindale中发现了两种不同的单倍型，它们的序列差异很大。来自孟加拉国的S. sindale与来自马来西亚和斯里兰卡的S. sindale形成了集群。来自孟加拉国的另一个来自泰国的S. sindale形成了一个集群。这两种单倍型的DNA序列差异与独立物种之间的差异相对应。此外，首次利用鼻血吸虫、隐种血吸虫和牛血吸虫分析了血吸虫mt DNA基因排列中的一个热点区ND4-ND1。结果表明，这三个来自亚洲和非洲的物种都是非洲型的。利用每个区域的DNA序列以及ND4-ND1区3个区域和CO1区域的串联序列进行系统发育分析，以确定隐种棘猴的分类位置。前者的分析显示了一个相当不稳定的树，而后者的分析显示了稳定和一致的树，特别是在属和种之间的系统发育关系方面。在这些调查中发现，不知名葡萄球菌最早从非洲群和籼稻群的共同祖先物种中分化出来。因此，这一结果否定了“隐姓埋名”从日本血吸虫类群的共同祖先分化而来的观点。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