Thiele Theresa, Kost Christian, Roces Flavio, Wirth Rainer
Plant Ecology and Systematics, University of Kaiserslautern, P.O. Box 3049, 67653, Kaiserslautern, Germany.
J Chem Ecol. 2014 Jun;40(6):617-20. doi: 10.1007/s10886-014-0460-y. Epub 2014 Jun 15.
Leaf-cutting ants (LCAs) are dominant herbivores of the Neotropics, as well as economically important pests. Their foraging ecology and patterns/mechanisms of food selection have received considerable attention. Recently, it has been documented that LCAs exhibit a delayed rejection of previously accepted food plants following treatment with a fungicide that makes the plants unsuitable as substrate for their symbiotic fungus. Here, we investigated whether LCAs similarly reject plants with induced chemical defenses, by combining analysis of volatile emissions with dual-choice bioassays that used LCA subcolonies (Atta sexdens L.). On seven consecutive days, foraging ants were given the choice between leaf disks from untreated control plants and test plants of Vitis vinifera ssp. vinifera L. treated with the phytohormone jasmonic acid (JA) to mimic herbivore attack. Chemical analysis revealed the emission of a characteristic set of herbivore-induced volatile organic compounds (VOC) from JA-induced plants. Dual-choice experiments indicated that workers did not show any preference initially, but that they avoided JA-treated plants from day five onwards. Our finding that A. sexdens foragers learn to avoid VOC-emitting plants, which are likely detrimental to their symbiotic fungus, represents the first evidence for avoidance learning in attine ants toward plants with induced defenses.
切叶蚁是新热带地区的主要食草动物，也是具有重要经济影响的害虫。它们的觅食生态学以及食物选择模式/机制受到了广泛关注。最近有文献记载，在用一种使植物不适于作为其共生真菌基质的杀菌剂处理后，切叶蚁对先前接受的食物植物表现出延迟的排斥反应。在此，我们通过将挥发性物质排放分析与使用切叶蚁亚群体（Atta sexdens L.）的双选生物测定相结合，研究了切叶蚁是否同样会排斥具有诱导性化学防御的植物。连续七天，给觅食的蚂蚁提供未处理的对照植物叶片圆盘和用植物激素茉莉酸（JA）处理过的酿酒葡萄（Vitis vinifera ssp. vinifera L.）试验植物叶片圆盘之间的选择，以模拟食草动物的攻击。化学分析表明，经JA诱导的植物会释放一组特征性的食草动物诱导挥发性有机化合物（VOC）。双选实验表明，工蚁最初没有表现出任何偏好，但从第五天起开始避开经JA处理的植物。我们发现，Atta sexdens觅食者学会避开释放VOC的植物，这些植物可能对它们的共生真菌有害，这是切叶蚁对具有诱导防御的植物产生回避学习的首个证据。
