Bologna Audrey, Detrain Claire
Service d'Ecologie Sociale, Université Libre de Bruxelles (ULB), Brussels, Belgium.
PLoS One. 2015 Sep 28;10(9):e0139365. doi: 10.1371/journal.pone.0139365. eCollection 2015.
Myrmecochorous diaspores bear a nutrient-rich appendage, the elaiosome, attractive to ant workers that retrieve them into the nest, detach the elaiosome and reject the seed intact. While this interaction is beneficial for the plant partner by ensuring its seed dispersal, elaiosome consumption has various effects -positive, negative or none - on ants' demography and survival, depending on both the ant/plant species involved. In this context, the contribution of ants to seed dispersal strongly varies according to the ant/plant pairs considered. In this paper, we investigate whether the dynamics of myrmecochory also vary on a temporal scale, for a given pair of partners: Myrmica rubra ants and Viola odorata seeds. During their first encounter with seeds, ants collect all the diaspores and eat the majority of elaiosomes. Both the harvesting effort and the elaiosome consumption decline when seeds are offered on the next week and completely cease for the following weeks. This is related to a decrease in the number of foragers reaching the food source, as well as to a reduced probability for an ant contacting a seed to retrieve it. Seed retrieval is not reactivated after seven weeks without any encounter with V. odorata seeds. By contrast, naive ant colonies only fed with fruit flies do not show a decline of prey harvesting of which the speed of retrieval even increases over the successive weeks. Myrmecochory may thus be labile at the scale of a fruiting season due to the ability of ants to steeply tune and cease for several months the harvesting of these seemingly poorly rewarding items and to maintain cessation of seed exploitation. The present study emphasizes the importance of a long-lasting follow up of the myrmecochory process, to assess the stability of this ant-plant partnership and to identify mechanisms of adaptive harvesting in ants.
蚁播植物的传播体带有一个富含营养的附属物，即油质体，它对蚂蚁工蚁具有吸引力，这些工蚁会将传播体带回巢穴，摘下油质体，然后完整地丢弃种子。虽然这种相互作用通过确保植物种子的传播对植物伙伴有益，但油质体的消耗对蚂蚁的种群统计学和生存有着各种影响——积极的、消极的或无影响——这取决于所涉及的蚂蚁/植物物种。在这种情况下，蚂蚁对种子传播的贡献因所考虑的蚂蚁/植物对的不同而有很大差异。在本文中，我们研究了对于特定的一对伙伴：红蚁（Myrmica rubra）和香堇菜（Viola odorata）种子，蚁播动态在时间尺度上是否也会有所不同。在首次接触种子时，蚂蚁收集了所有传播体并吃掉了大部分油质体。当第二周提供种子时，采集努力和油质体消耗都下降了，并且在接下来的几周完全停止。这与到达食物源的觅食者数量减少以及蚂蚁接触种子以取回种子的概率降低有关。在七周没有遇到香堇菜种子后，种子取回行为不会重新激活。相比之下，只喂食果蝇的未接触过种子的蚁群并没有表现出猎物采集量的下降，其取回速度甚至在连续几周内有所增加。因此，由于蚂蚁能够迅速调整并停止对这些看似回报不佳的物品的采集数月之久，并维持种子利用的停止，蚁播在一个结果季节的尺度上可能是不稳定的。本研究强调了对蚁播过程进行长期跟踪的重要性，以评估这种蚂蚁 - 植物伙伴关系的稳定性，并确定蚂蚁适应性采集的机制。
