Evolutionary biology of the process of host shift in phytophagous ladybird beetles

1. 研究了寄生瓢虫复合体（Epilachna viintioctomaculata complex）与寄主植物的共进化关系。对瓢虫同工酶和mtDNA的分析表明：(1)瓢虫的寄主转移发生在很短的进化时间内，从茄科植物转移到其他科植物（菊科、罂粟科、小檗科等），现在被某些成员利用；(2)同种异域居群之间的遗传差异是由“距离隔离”造成的；(3)寄主特异性是共存的同域居群成员之间重要的生殖屏障。对北海道南部地区主要寄主植物之一的蓟（Cirsium）的分子、形态和物候分析表明，尽管它们在形态和生态上存在差异，但它们在遗传上非常相似，这表明可能在冰川期，北海道及其周边地区发生了快速的种系辐射。虽然不是所有的蓟科植物都适合作为瓢虫的寄主植物，但瓢虫利用的蓟科植物并不构成一个单系集群。麝香草中所含的一种物质被鉴定为麝香草苷，这种物质可以防止以麝香草为食的蓟侵染。但该类黄酮不会引起另一种取食蓟的E. pustlosa的摄食排斥反应。研究了不同地理来源和寄主植物的不同居群在不同寄主植物上生长性能的遗传背景，并进行了比较。这些结果表明，为了适应当地的食物环境，不同成员的寄主植物的转移进行得非常迅速。瓢虫的低灵敏性可能促进了这一过程。少

1. Coevolutionary relationships between the phytophagous ladybird beetles of the Epilachna vigintioctomaculata complex and their host plants were investigated. Analyses of allozymes and mtDNA of the ladybird beetles suggested that (1) host shift in the ladybird beetles occurred during a very short evolutionary time, from solanaceous plants to plants of other families (Asteraceae, Papaveraceae, Berberidaceae, etc.) now utilized by certain members; (2) genetic difference between conspecific allopatric populations was resulted from the "isolation by distance": and (3) host specificity functions as a crucial reproductive barrier between coexisting sympatric members of the E. vigintioctomaculata complex.2. Molecular, morphometric, and phenological analyses of thistles (Cirsium), one of the major host plants of the E. viglntioctomaculata complex, distributed in the southern part of Hokkaido revealed that they are genetically very similar to each other in spite of their distinct morphological … More and ecological differences, suggesting that an ancestral Cirsium species underwent rapid phyletic radiation in Hokkaido and surrounding areas, perhaps during the glacial period. Although not all thistles are suitable as the host plants of the ladybird beetles, thistle species utilized by the ladybird beetles did not constitute a monophyletic cluster.3. The substance contained in Cirsium kagamontanum, that act as a feeding deterrent against infestation by a thistle feeding E. niponica, was identified as pectolinarin. But this flavonoid did not induce feeding rejection by another thistle feeding species E. pustulosa.4. Genetic background of growth performance on different host plants was studied and compared between different populations of E. vigintioctolmaculata with different geographic origins and host plants.5. These results suggests that the shift of host plants in various members of the E. vigintioctomaculata complex proceeded very rapidly, as adaptation to local food environments. Low vagility of the ladybird beetles may have enhanced this process . Less