| Project/Area Number |
16570075
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| Research Category |
Grant-in-Aid for Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
Biodiversity/Systematics
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| Research Institution | Kobe University |
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Principal Investigator |
NAITO Tikahiko Kobe University, Faculty of Agriculture, Professor, 農学部, 教授 (70031226)
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| Project Period (FY) |
2004 – 2005
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| Project Status |
Completed (Fiscal Year 2005)
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| Budget Amount *help |
¥3,700,000 (Direct Cost: ¥3,700,000)
Fiscal Year 2005: ¥1,200,000 (Direct Cost: ¥1,200,000)
Fiscal Year 2004: ¥2,500,000 (Direct Cost: ¥2,500,000)
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| Keywords | sympatric speciation / monophagous / host shift / parapatric speciation / chromosome polymorphism / fitness / triploid thelytoky / ニホントガリシダハバチ / カタアカスギナハバチ / タビラコハバチ / 一方向選択交尾 / 雌性産生単為発生 / 寄生転換 |
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| Research Abstract |
1.Sympatric speciation based on the host shift in Hemitaxonus japonicus complex : The polyblepharum host race is speciating from the tripteron host race with host shift on the narrow zone (ca.10km) at 33 °40'N in the Kii Peninsula, without geological isolation. Synergistic effects of four reproductive isolation factors could produce the new host race under the sympatric condition : (1)disruptive host selection by one-locus gene ; (2)assortative mating among adults with the same host selection gene on each host plant ; (3)non-survival of the new host race larvae on the old host plant caused by the conditioning effect that the new host race female continues to lay eggs on the new host plant ; (4)one-way selective mating where the new host race male can not mate with the old host race female prevents the gene flow from the old host race to the new host race and establishes the genetic independence for the new host race.
2.Parapatric speciation of Loderus genucinctus by chromosome rearrangements : This sawfly broadly distributed in Japan from Hokkaido to Kyushu has Robertson' chromosome polymorphism of n=9, n=10 and n=11. Ancestral karyotype is n=9, and n=10 and n=11 karyotypes have been derived by central fission of two large metacentric chromosomes of n=9. Derived karyotypes are extending the distribution range and expelling the range of the older types. The n=9 and n=11 karyotypes are distributed parapatrically without any overlap. These two populations are reproductively isolated, because their heterozygous females are lethal, and the difference of the fitness among two karyotypes seems a key factor of the distribution shift.
3.Punctual speciation of 3n thelytoky sawfly : Pachyprotasis youngiae is the first example of 3n thelytoky in Hymenoptera. It is suggested that this sawfly has arised from the related species by punctual speciation with chromosome duplication.
4.Generalization : There are several types of non-allopatric speciation in monophagous sawflies.
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