Schiestl Florian P, Kirk Heather, Bigler Laurent, Cozzolino Salvatore, Desurmont Gaylord A
Institute of Systematic Botany, University of Zürich, Zollikerstrasse 107, 8008, Zürich, Switzerland.
New Phytol. 2014 Jul;203(1):257-66. doi: 10.1111/nph.12783. Epub 2014 Mar 28.
Plant defense against herbivores may compromise attraction of mutualists, yet information remains limited about the mechanisms underlying such signaling tradeoffs. Here, we investigated the effects of foliar herbivory by two herbivore species on defense compounds, floral signaling, pollinator and parasitoid attraction, and seed production. Herbivory generally reduced the quantity of many floral volatile organic compounds VOCs) in Brassica rapa. By contrast, floral color, flower diameter, and plant height remained unaffected. The decreased amounts of floral volatiles led to reduced attractiveness of flowers to pollinators, but increased the attractiveness of herbivore-infested plants to parasitoids. Plants infested with the native butterfly Pieris brassicae produced more flowers during early flowering, effectively compensating for the lower olfactory attractiveness. Herbivory by the invasive Spodoptera littoralis increased the amounts of glucobrassicanapin, and led to delayed flowering. These plants tended to attract fewer pollinators and to produce fewer seeds. Our study indicates a tradeoff between pollinator attraction and indirect defense (parasitoid attraction), which can be mitigated by reduced floral VOC emission and production of more early flowers. We suggest that this compensatory mechanism is specific to plant-herbivore associations with a coevolutionary history.
植物对食草动物的防御可能会影响互利共生者的吸引力，但关于这种信号权衡背后的机制，相关信息仍然有限。在此，我们研究了两种食草动物的叶片取食对防御化合物、花香信号、传粉者和寄生蜂吸引力以及种子产量的影响。取食通常会减少白菜型油菜中许多花香挥发性有机化合物（VOCs）的含量。相比之下，花色、花径和株高不受影响。花香挥发物含量的减少导致花朵对传粉者的吸引力降低，但增加了受食草动物侵害的植物对寄生蜂的吸引力。被本地蝴蝶菜粉蝶侵害的植物在开花初期会产生更多花朵，有效弥补了较低的嗅觉吸引力。入侵的斜纹夜蛾取食会增加葡糖菜子硫苷的含量，并导致开花延迟。这些植物往往吸引较少的传粉者，产生较少的种子。我们的研究表明传粉者吸引力与间接防御（寄生蜂吸引力）之间存在权衡，这种权衡可以通过减少花香VOC排放和产生更多早花来缓解。我们认为这种补偿机制特定于具有共同进化历史的植物 - 食草动物关联。
