Yamaga Yuriko, Ohgushi Takayuki
Institute of Low Temperature Science, Hokkaido University, Sapporo 060-0819, Japan, , , , , , JP.
Oecologia. 1999 May;119(2):183-190. doi: 10.1007/s004420050775.
We investigated the relationship between oviposition preference and offspring performance in a herbivorous lady beetle Epilachna pustulosa on two co-occurring plant species, thistle Cirsium kamtschaticum and blue cohosh Caulophyllum robustum, in 1994 and 1995. The relative importance of bottom-up effects by host plants and top-down effects by natural enemies on offspring performance were determined using field and laboratory experiments. In both years, egg density on blue cohosh was significantly higher than on thistle. A laboratory experiment demonstrated that larval survival from hatching to adult emergence was significantly higher, and developmental period shorter when larvae were reared on blue cohosh compared to thistle. The positive preference-performance linkage varied between years in the field. Top-down effects had a different impact on larval survival on the two host plant species. Arthropod predators, a lady beetle Harmonia axyridis and an earwig Forficula mikado, considerably depressed immature survival on thistle, while they were negligible on blue cohosh. Although the lack of effective predation increased larval survival on blue cohosh, it led to defoliation due to increased larval feeding late in the season. Because of severe intraspecific competition, old larvae had significantly lower survival on blue cohosh than on thistle. In 1994, as larval survival decreased due to defoliation on blue cohosh, the overall survival rate was significantly higher on thistle than on blue cohosh. This survival pattern was opposite to that found in the laboratory experiment. In contrast, in 1995, the increase in predatory lady beetles on thistle caused greater larval mortality. Thus, the overall survival was significantly lower on thistle than on blue cohosh, although severe intraspecific competition occurred on blue cohosh as it had in 1994. Consequently, the offspring performance on the two host plants is largely determined by the relative importance of arthropod predation determining larval survival on thistle and host plant defoliation reducing late larval survival on blue cohosh. These results indicate the important role of spatial and temporal variability of natural enemies on the preference-performance linkage of herbivorous insects.
1994年和1995年，我们研究了食草性瓢虫茄二十八星瓢虫（Epilachna pustulosa）在两种共生植物物种——刺儿菜（Cirsium kamtschaticum）和类叶升麻（Caulophyllum robustum）上产卵偏好与后代表现之间的关系。通过田间和实验室实验，确定了寄主植物的自下而上效应和天敌的自上而下效应对后代表现的相对重要性。在这两年中，类叶升麻上的卵密度显著高于刺儿菜。一项实验室实验表明，与在刺儿菜上饲养相比，幼虫从孵化到成虫羽化的存活率显著更高，且在类叶升麻上饲养时发育周期更短。在田间，这种正向的偏好 - 表现联系在不同年份有所不同。自上而下效应在两种寄主植物物种上对幼虫存活率有不同影响。节肢动物捕食者，一种瓢虫异色瓢虫（Harmonia axyridis）和一种蠼螋日本蠼螋（Forficula mikado），显著降低了刺儿菜上未成熟个体的存活率，而在类叶升麻上它们的影响可忽略不计。虽然缺乏有效捕食增加了类叶升麻上幼虫的存活率，但这导致了因季节后期幼虫取食增加而造成的落叶。由于激烈的种内竞争，大龄幼虫在类叶升麻上的存活率显著低于在刺儿菜上的存活率。1994年，由于类叶升麻上的落叶导致幼虫存活率下降，刺儿菜上的总体存活率显著高于类叶升麻。这种存活模式与实验室实验中发现的相反。相比之下，1995年，刺儿菜上捕食性瓢虫数量的增加导致了更高的幼虫死亡率。因此，尽管类叶升麻上像1994年一样发生了激烈的种内竞争，但刺儿菜上的总体存活率显著低于类叶升麻。因此，两种寄主植物上的后代表现很大程度上取决于节肢动物捕食对刺儿菜上幼虫存活的影响以及寄主植物落叶对类叶升麻上大龄幼虫存活的影响的相对重要性。这些结果表明了天敌的时空变异性在食草昆虫偏好 - 表现联系中的重要作用。
