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Studies on the sympatric host shift mechanism in monophagous sawflies

单食性锯蝇同域寄主转移机制的研究

基本信息

批准号：
62560043
负责人：
NAITO Tikahiko
金额：
$ 1.34万
依托单位：
Kobe University
依托单位国家：
日本
项目类别：
Grant-in-Aid for General Scientific Research (C)
财政年份：
1987
资助国家：
日本
起止时间：
1987 至 1989
项目状态：
已结题

项目摘要

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.

1.同域性寄主小种的形成与寄主转移发生在蕨类叶蜂Hemitaxonus nerve分布的南部界限附近。这是首次发现单食性昆虫在田间共域形成寄主小种.在纪伊半岛，从北向南约10 km范围内，耳蕨Polystichum tripteron和耳蕨P. polyblepharum的成虫寄主选择性和幼虫存活率均发生显著变化。33 ° 40 ′ N，新的寄主小种--多眼小种正在形成，没有地理隔离。该叶蜂在该带以南为寡食性，而在该带以北为生殖隔离带，可分为两个寄主小种：tripteron小种和polyblepharum小种.成虫对寄主的选择性可能受一个基因座上的两个等位基因控制：A是雷公藤素选择性等位基因，A是多睑等位基因，它是A的突变体。幼虫的存活率也可能受单个位点的等位基因控制，但多眼蕨特异性等位基因可能不是通过突变而是由于多眼蕨多代产卵的条件作用而从寡食等位基因衍生而来.三种隔离机制在同域寄主小种形成中起重要作用。破坏性选择和选择性交配是交配前的隔离，交配偏好是交配后的隔离.鉴定该复合体中与成虫寄主选择或交配选择有关的化学物质是今后研究中需要解决的重要问题。