| Co-Investigator(Kenkyū-buntansha) |
SASAKI Go JT Biohistory Research Hall, Laboratory Sector, Post doctoral Fellow (90426651)
MIYATA Takashi JT Biohistory Research Hall, 常勤顧問 (20022692)
IWABE Naoyuki Kyoto University, Graduate School of Science, Assistant Professor (80263060)
OHOBAYASHI Nobuo Ehime University, Faculty of Agriculture, 教授 (20253320)
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| Budget Amount *help |
¥3,200,000 (Direct Cost: ¥3,200,000)
Fiscal Year 2006: ¥1,100,000 (Direct Cost: ¥1,100,000)
Fiscal Year 2005: ¥2,100,000 (Direct Cost: ¥2,100,000)
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| Research Abstract |
In recent years, molecular phylogenetic analyses have rejected a traditional view that Hexapoda evolved from Myriapoda, and uncovered a fact that Hexapods and Crustacea form a common clade, which is now called Pancrustacea. However, the origin of Hexapoda is still a controversial issue. The key point is that the phylogenetic position of entognathans including three wingless insect orders (Collembola, Diplura and Protura) is unclear. Recent phylogenetic studies using mitochondrial proteins challenged the traditional view of monophyly of Hexapoda, and indicate that entognathans and the remainder (ectognathans) of hexapods do not have a common ancestor, and some crustaceans are closer to ectognathans. On the other hand, analyses based on some nuclear DNA sequences still support the monophyly of hexapods.
To resolve this issue, we have sequenced three nuclear genes encoding the catalytic subunit of DNA polymerase delta and largest and second largest subunit of RNA polymerase II from arthropods. The amino acid sequences of these proteins were subjected to a phylogenetic analysis based on the maximum likelihood method. The resulting tree showed that hexapods are the monophyletic group. The result also suggests that the order Protura is the basal lineage among all hexapods.
Further analyses using these genes for winged insects perfectly elucidated the phylogenetic relationships among all the orders of holometabolous insects. The phylogenetic tree showed that holometabolous insects divided into three major groups : the first one includes the sole order, Hymenoptera, the second group consists of three orders, Neuroptera, Coleoptera and Strepsiptera, the last group comprises five orders, Diptera, Siphonaptera, Mecoptera, Trichoptera and Lepidoptera. A new finding was also found in this analysis that the order Hymenoptera is the most basal lineage among all holometabolous insects.
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