1989 Fiscal Year Final Research Report Summary
Studies on the sympatric host shift mechanism in monophagous sawflies
Project/Area Number |
62560043
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Research Category |
Grant-in-Aid for General Scientific Research (C)
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Allocation Type | Single-year Grants |
Research Field |
植物保護
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Research Institution | Kobe University |
Principal Investigator |
NAITO Tikahiko Kobe University, Agriculture, Associate Professor, 農学部, 助教授 (70031226)
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Project Period (FY) |
1987 – 1989
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Keywords | Host race / Host preference gene / Larval survival gene / Disruptive selection / Assortative mating / Mating preference / Conditioning |
Research Abstract |
1. Sympatric host race formation with host shift is occurring near the southern limit of distribution in the fern sawfly Hemitaxonus japonicus. This is the first discovery that monophagous insects forming host races sympatrically in the field. 2. In the Kii peninsula, the adult host preference and larval survival for two species of ferns, Polystichum tripteron and P. polyblepharum, are remarkably changing in this sawfly within about 10km from north to south near lat. 33゚40'N, where the new host race, polyblepharum race is being formed without geographical isolation. This sawfly is oligophagous south of the zone, while it is divided into two host races, tripteron race and polyblepharum race, north of the zone with reproductive isolation. 3. Adult host preference may be controlled by two alleles at a single locus: A means the tripteron preference allele and A means the polyblepharum allele which is a mutant from A. Larval survival may be also controlled by alleles at a single locus, but the polyblepharum-specific allele might have been derived from the oligophagous allele not by mutation but by conditioning due to oviposition to polyblepharum fern for many generations. 4. Three isolation mechanisms play important roles for sympatric host race formation in this sawfly. Disruptive selection and assortative mating act as a premating isolation and mating preference works as a postmating isolation. 5. Identification of chemical compounds concerned with adult host preference or with mating preference in this species complex is an important problem to solve in future studies.
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Research Products
(6 results)