Department of Biology, Technical University Darmstadt, Schnittspahnstrasse 3, 64287 Darmstadt, Germany.
J Chem Ecol. 2012 Sep;38(9):1093-104. doi: 10.1007/s10886-012-0174-y. Epub 2012 Aug 18.
Elaiosomes of myrmecochorous plant seeds are known to enhance the attraction of diaspore-dispersing ants by serving as a nutritional reward. However, it remained unclear which (nutritional) compounds affect diaspore preferences of ants. We hypothesized that apart from elaiosome/seed-size ratio, volume, and physical surface of diaspores, the quantity and the composition of fatty acids, amino acids, and sugars strongly influence the diaspore preferences of different species. Chemical (nutritional) profiles as well as structural properties of seeds with and without elaiosomes were analyzed and correlated with observed seed choice behavior of ants. Cafeteria experiments in the field confirmed the enhanced attractiveness of elaiosome-bearing seeds for all three ant species tested (Lasius fuliginosus, Myrmica ruginodis, and Temnothorax nylanderi), although seeds lacking elaiosomes also were transported. In multiple-choice cafeteria experiments with simultaneously offered diaspores of 16 plant species with and without elaiosome and with highly varying structural and chemical properties, all three ant species showed distinct preferences for certain diaspore species. Correlation analyses confirmed that the presence of an elaiosome represents the crucial factor that favors ant diaspore dispersal. In addition, the composition and the content of free amino acids, and to varying degrees fatty acids, were found to significantly affect preferences of each ant species, whereas the effect of single fatty acids acting as chemical triggers for diaspore transport by ants, as supposed by several studies, was not confirmed. In conclusion, although at least some diaspore species lacking elaiosomes attract ants for diaspore removal services by presenting nutritional seed coats, the production of elaiosomes seems to provide a worthwhile investment. Elaiosomes ensure rapid diaspore detection and removal due to chemical cue compounds and by offering a highly nutritional food supply, probably fitting the nutritional demands of ants.
植物种皮上的油性胚乳被认为是作为营养奖励，从而增强了传播种子的蚂蚁对分散体的吸引力。然而，目前尚不清楚哪些（营养）化合物会影响蚂蚁对分散体的偏好。我们假设，除了种皮/种子大小的比例、体积和种子的物理表面外，脂肪酸、氨基酸和糖的数量和组成强烈影响不同物种对分散体的偏好。我们分析了有和没有油性胚乳的种子的化学（营养）概况和结构特性，并将其与蚂蚁观察到的种子选择行为相关联。在野外的自助餐厅实验中，证实了有油性胚乳的种子对所有三种测试蚂蚁（黑腹毛足蚁、红林蚁和尼氏叶齿猛蚁）的吸引力增强，尽管没有油性胚乳的种子也被搬运。在有和没有油性胚乳的 16 种植物分散体的同时提供的多选择自助餐厅实验中，这些植物具有高度变化的结构和化学特性，所有三种蚂蚁都表现出对某些分散体物种的明显偏好。相关分析证实，油性胚乳的存在是有利于蚂蚁传播分散体的关键因素。此外，游离氨基酸的组成和含量，以及在不同程度上的脂肪酸，被发现显著影响每种蚂蚁的偏好，而一些研究假设的作为蚂蚁传播分散体的化学触发物的单一脂肪酸的作用则没有得到证实。总之，尽管至少有一些没有油性胚乳的分散体通过呈现营养丰富的种皮来吸引蚂蚁来获取分散体，但油性胚乳的产生似乎提供了一个值得的投资。油性胚乳通过化学线索化合物和提供高营养的食物供应来确保快速检测和移除分散体，这可能符合蚂蚁的营养需求。
