Zvereva E L, Rank N E
Section of Ecology, Department of Biology, University of Turku, 20014 Turku, Finland.
Oecologia. 2003 Apr;135(2):258-67. doi: 10.1007/s00442-003-1184-9. Epub 2003 Feb 22.
Larvae of the leaf beetle Chrysomela lapponica obtain salicyl glucosides (SGs) from the host plant to produce a defensive secretion with salicylaldehyde. In northern Russia, larvae and pupae experience high parasitism by the phorid fly Megaselia opacicornis and tachinid fly Cleonice nitidiuscula. We compared the suitability of the SG-rich Salix borealis and SG-poor S. caprea and S. phylicifolia to Ch. lapponica and tested whether enemy pressure on Ch. lapponica varies among host species that differ in SG content. In the laboratory, survival of Ch. lapponica larvae was higher on S. borealis than on S. caprea and S. phylicifolia, while adult body mass was higher on S. borealis and S. caprea than on S. phylicifolia. In the field, parasitism by both M. opacicornis and Cl. nitidiuscula was greater on beetles from S. borealis than from the SG-poor S. caprea or S. phylicifolia. In a laboratory choice test, the pupal parasitoid M. opacicornis laid similar numbers of eggs on beetles reared on SG-rich and SG-poor willows, suggesting that the host plant-derived defence is not effective against this parasitoid. In a field enemy-exclusion experiment, beetle survival was greatly enhanced by the exclusion of enemies, but survival rates did not differ between S. borealis and S. caprea, although larvae developed faster on S. borealis. On the other hand, parasitism and predation were observed more often on S. borealis than on S. caprea. Thus, beetle larvae perform better but also suffer higher predation and parasitism on S. borealis than on SG-poor willows. Ch. lapponica does not appear to obtain enemy-free space by feeding on SG-rich willow species.
叶甲Chrysomela lapponica的幼虫从寄主植物中获取水杨苷（SGs），以产生含有水杨醛的防御性分泌物。在俄罗斯北部，幼虫和蛹遭受隐角大蚤蝇Megaselia opacicornis和亮突赘寄蝇Cleonice nitidiuscula的高寄生率。我们比较了富含SG的北极柳Salix borealis以及SG含量低的欧洲山杨S. caprea和柳叶菜柳S. phylicifolia对Ch. lapponica的适宜性，并测试了Ch. lapponica所面临的天敌压力在SG含量不同的寄主物种之间是否存在差异。在实验室中，Ch. lapponica幼虫在北极柳上的存活率高于在欧洲山杨和柳叶菜柳上，而成虫体重在北极柳和欧洲山杨上高于柳叶菜柳。在野外，北极柳上的甲虫遭受隐角大蚤蝇和亮突赘寄蝇的寄生率高于SG含量低的欧洲山杨或柳叶菜柳上的甲虫。在实验室选择试验中，蛹寄生蜂隐角大蚤蝇在以富含SG和SG含量低的柳树饲养的甲虫上产下的卵数相似，这表明寄主植物衍生的防御对这种寄生蜂无效。在野外天敌排除实验中，排除天敌极大地提高了甲虫的存活率，但北极柳和欧洲山杨之间的存活率没有差异，尽管幼虫在北极柳上发育得更快。另一方面，在北极柳上观察到的寄生和捕食现象比在欧洲山杨上更频繁。因此，与SG含量低的柳树相比，甲虫幼虫在北极柳上生长得更好，但也遭受更高的捕食和寄生率。Ch. lapponica似乎无法通过取食富含SG的柳树物种来获得无天敌空间。
