van Dam N M, Hadwich K, Baldwin I T
Max Planck Institute for Chemical Ecology, Tatzendpromenade 1A, D-07745 Jena, Germany e-mail:
Freie Universität Berlin, Institut für Zoologie, Haderslebenerstrasse 9, D-12163 Berlin, Germany, , , , , , DE.
Oecologia. 2000 Feb;122(3):371-379. doi: 10.1007/s004420050043.
Many plants employ induced responses against generalist herbivores. Specialist herbivores, however, may employ several mechanisms to overcome the negative effects of induced plant defenses. Here we test how the behavior and development of specialist Manduca sexta larvae are affected by induced responses in their natural host plant Nicotiana attenuata. On a spatial scale relevant to both the plant and the herbivore, we first determined how methyl jasmonate (MeJA)-induced responses, such as increased nicotine production, affect the tendency of larvae to leave induced plants. When larvae were allowed to move between two plants planted in one pot, they left an MeJA-treated plant faster than a control plant. When both plants in the pot were MeJA-treated, the larvae developed more slowly than when both plants were uninduced, or when the larvae had the opportunity to move to an uninduced neighbor. The sooner larvae moved from an MeJA-treated plant to an untreated neighbor, the larger the body mass they attained. This demonstrates that M. sexta larvae can compensate behaviorally for the deleterious effects of induced plant responses. These effects were observed in plants grown under both low and high N supply rates, though the effects were more pronounced under high N. To examine the consequences of the timing and the direction of the host plant switching behavior for larval development, neonate larvae were fed leaves excised from induced and uninduced plants. Larvae confined to MeJA-treated leaves had higher mortality rates and grew slower than larvae fed only control leaves. This demonstrates that MeJA-induced responses decrease growth and development of specialist herbivores that do not have the behavioral option of moving to an uninduced plant. The sooner the larvae were switched to MeJA-treated leaves, the slower their development compared to larvae fed only uninduced leaves. In contrast, the sooner larvae fed MeJA-treated leaves were switched to control leaves, the faster they developed. Again the effects of MeJA treatment were stronger in plants grown under high N supply. We propose that induced plants growing in close competition with an uninduced conspecific may offset the fitness costs of these induced responses and perhaps obtain a fitness benefit by motivating herbivores to move to their neighboring competitors.
许多植物会对多食性食草动物产生诱导反应。然而，专食性食草动物可能会采用多种机制来克服植物诱导防御的负面影响。在此，我们测试专食性烟草天蛾幼虫的行为和发育如何受到其天然寄主植物黄花烟草诱导反应的影响。在与植物和食草动物都相关的空间尺度上，我们首先确定了茉莉酸甲酯（MeJA）诱导的反应，如尼古丁产量增加，如何影响幼虫离开诱导植物的倾向。当幼虫被允许在种植于一个花盆中的两株植物之间移动时，它们离开经MeJA处理的植物的速度比对照植物更快。当花盆中的两株植物都经MeJA处理时，幼虫的发育比两株植物都未被诱导时，或者幼虫有机会移至未被诱导的相邻植物时更慢。幼虫越早从经MeJA处理的植物移至未处理的相邻植物，它们获得的体重就越大。这表明烟草天蛾幼虫能够通过行为来补偿植物诱导反应的有害影响。在低氮和高氮供应率下生长的植物中都观察到了这些影响，尽管在高氮条件下影响更为明显。为了研究寄主植物转换行为的时间和方向对幼虫发育的影响，将初孵幼虫喂食从诱导和未诱导植物上切下的叶子。与仅喂食对照叶子的幼虫相比，被限制在经MeJA处理的叶子上的幼虫死亡率更高且生长更慢。这表明MeJA诱导的反应会降低没有移至未被诱导植物这一行为选择的专食性食草动物的生长和发育。与仅喂食未诱导叶子的幼虫相比，幼虫越早被转换至经MeJA处理的叶子上，其发育就越慢。相反，喂食经MeJA处理叶子的幼虫越早被转换至对照叶子上，它们发育得就越快。同样，在高氮供应下生长的植物中，MeJA处理的影响更强。我们提出，与未被诱导的同种植物紧密竞争生长的诱导植物可能会抵消这些诱导反应的适合度成本，并且或许通过促使食草动物移至其相邻的竞争者而获得适合度益处。
