Increased Host Investment in Extrafloral Nectar (EFN) Improves the Efficiency of a Mutualistic Defensive Service
Increased Host Investment in Extrafloral Nectar (EFN) Improves the Efficiency of a Mutualistic Defensive Service
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DOI：
10.1371/journal.pone.0046598
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发表时间：
2012-10-04
期刊：
影响因子：
3.7
通讯作者：
Boland, Wilhelm
中科院分区：
文献类型：
--
作者：
Gonzalez-Teuber, Marcia;Silva Bueno, Juan Carlos;Boland, Wilhelm
花外花蜜是植物通过吸引防御蚂蚁来进行间接防御的重要物质。然而，就像在互惠共生的背景下产生的所有奖励一样，EFN有被非蚂蚁消费者利用的危险，这些消费者不保护植物免受食草动物的侵害。在这里，我们问工厂，通过投资更多的EFN，是否可以改善他们的间接防御，或者更确切地说，增加损失的风险，这种投资的EFN小偷。我们使用的专性植物蚂蚁金合欢-Pseudomyrmex系统和实验研究在该领域在干旱和雨季如何EFN分泌的变化有关（i）蚂蚁活动，（ii）蚂蚁介导的防御草食动物和（iii）EFN的非蚂蚁消费者的剥削。花外投资增强蚂蚁招聘，并与蚂蚁介导的防御草食动物。蚂蚁介导的保护剥削者也增加了花蜜糖浓度的比例。虽然EFN产量的每日高峰与EFN窃贼的最高活动相吻合，但Pseudomyrmex ferrugineus蚂蚁有效地保护了这一资源。然而，蚂蚁的防御效果在季节之间存在差异。在旱季，植物生长缓慢，分泌更多的EFN比在雨季，因此，经历了更高水平的蚂蚁介导的间接防御。我们的研究结果表明，增加植物投资的间接防御性状，可以提高由此产生的防御服务对食草动物和剥削者。专性蚂蚁植物的EFN分泌代表了一种防御特征，其投资水平与所获得的有益效果正相关。
Extrafloral nectar (EFN) plays an important role as plant indirect defence through the attraction of defending ants. Like all rewards produced in the context of a mutualism, however, EFN is in danger of being exploited by non-ant consumers that do not defend the plant against herbivores. Here we asked whether plants, by investing more in EFN, can improve their indirect defence, or rather increase the risk of losing this investment to EFN thieves. We used the obligate plant-ant Acacia-Pseudomyrmex system and examined experimentally in the field during the dry and the rainy seasons how variations in EFN secretion are related to (i) ant activity, to (ii) the ant-mediated defence against herbivores and (iii) the exploitation of EFN by non-ant consumers. Extrafloral investment enhanced ant recruitment and was positively related to the ant mediated defence against herbivores. The ant-mediated protection from exploiters also increased in proportion to the nectar sugar concentration. Although the daily peak of EFN production coincided with the highest activity of EFN thieves, Pseudomyrmex ferrugineus ants protected this resource effectively from exploiters. Nevertheless, the defensive effects by ants differed among seasons. During the dry season, plants grew slower and secreted more EFN than in the rainy season, and thus, experienced a higher level of ant-mediated indirect defence. Our results show that an increased plant investment in an indirect defence trait can improve the resulting defensive service against both herbivores and exploiters. EFN secretion by obligate ant-plants represents a defensive trait for which the level of investment correlates positively with the beneficial effects obtained.