Laboratory of Apiculture and Social Insects, School of Life Sciences, University of Sussex, Falmer, United Kingdom.
PLoS One. 2012;7(9):e44501. doi: 10.1371/journal.pone.0044501. Epub 2012 Sep 12.
Positive feedback plays a major role in the emergence of many collective animal behaviours. In many ants pheromone trails recruit and direct nestmate foragers to food sources. The strong positive feedback caused by trail pheromones allows fast collective responses but can compromise flexibility. Previous laboratory experiments have shown that when the environment changes, colonies are often unable to reallocate their foragers to a more rewarding food source. Here we show both experimentally, using colonies of Lasius niger, and with an agent-based simulation model, that negative feedback caused by crowding at feeding sites allows ant colonies to maintain foraging flexibility even with strong recruitment to food sources. In a constant environment, negative feedback prevents the frequently found bias towards one feeder (symmetry breaking) and leads to equal distribution of foragers. In a changing environment, negative feedback allows a colony to quickly reallocate the majority of its foragers to a superior food patch that becomes available when foraging at an inferior patch is already well underway. The model confirms these experimental findings and shows that the ability of colonies to switch to a superior food source does not require the decay of trail pheromones. Our results help to resolve inconsistencies between collective foraging patterns seen in laboratory studies and observations in the wild, and show that the simultaneous action of negative and positive feedback is important for efficient foraging in mass-recruiting insect colonies.
正反馈在许多动物集体行为的出现中起着重要作用。在许多蚂蚁中，信息素轨迹招募并引导同巢觅食者前往食物源。轨迹信息素产生的强烈正反馈允许快速的集体反应，但会降低灵活性。以前的实验室实验表明，当环境发生变化时，蚁群通常无法将觅食者重新分配到更有回报的食物源。在这里，我们使用黑褐林蚁的蚁群进行了实验，并通过基于代理的模拟模型表明，在觅食地点拥挤造成的负反馈允许蚂蚁即使在强烈招募到食物源的情况下也能保持觅食的灵活性。在恒定环境中，负反馈可防止常见的对一个喂食器的偏向（对称性破坏），并导致觅食者的均匀分布。在变化的环境中，负反馈允许蚁群快速将大部分觅食者重新分配到一个优越的食物斑块上，当在一个较差的斑块上觅食已经进行得很好时，这个斑块就会变得可用。该模型证实了这些实验结果，并表明蚁群切换到优越食物源的能力不需要轨迹信息素的衰减。我们的研究结果有助于解决实验室研究中观察到的集体觅食模式与野外观察之间的不一致，并表明负反馈和正反馈的同时作用对于大规模招募昆虫蚁群的有效觅食至关重要。
