Larsen Janni, Fouks Bertrand, Bos Nick, d'Ettorre Patrizia, Nehring Volker
Centre for Social Evolution, University of Copenhagen, Universitetsparken 15, 2100 Copenhagen E, Denmark.
J Insect Physiol. 2014 Nov;70:59-66. doi: 10.1016/j.jinsphys.2014.09.002. Epub 2014 Sep 6.
A key feature for the success of social insects is division of labour, allowing colony members to specialize on different tasks. Nest defence is a defining task for social insects since it is crucial for colony integrity. A particularly impressive and well-known case of worker specialization in complex hymenopteran societies is found in leaf-cutting ants of the genera Atta and Acromyrmex. We hypothesized that three morphological worker castes of Acromyrmex echinatior differ in their likelihood to attack intruders, and show that major workers are more aggressive towards non-nestmate workers than medium and minor workers. Moreover, minors do not discriminate between nestmate and non-nestmate brood, while larger workers do. We further show that A. echinatior ants use cuticular chemical compounds for nestmate recognition. We took advantage of the natural variation in the cuticular compounds between colonies to investigate the proximate factors that may have led to the observed caste differences in aggression. We infer that major workers differ from medium workers in their general propensity to attack intruders (the "action component" of the nestmate recognition system), while minors seem to be less sensitive to foreign odours ("perception component"). Our results highlight the importance of proximate mechanisms underlying social insect behaviour, and encourage an appreciation of intra-colony variation when analysing colony-level traits such as nest defence.
社会性昆虫成功的一个关键特征是劳动分工，这使得群体成员能够专门从事不同的任务。巢穴防御是社会性昆虫的一项决定性任务，因为它对群体的完整性至关重要。在切叶蚁属（Atta）和顶切叶蚁属（Acromyrmex）的切叶蚁中，发现了复杂膜翅目社会中一个特别令人印象深刻且广为人知的工蚁专业化案例。我们假设，棘刺顶切叶蚁（Acromyrmex echinatior）的三种形态的工蚁在攻击入侵者的可能性上存在差异，并表明大型工蚁比中型和小型工蚁对非巢友工蚁更具攻击性。此外，小型工蚁不会区分巢友和非巢友的幼虫，而大型工蚁会。我们进一步表明，棘刺顶切叶蚁利用表皮化学化合物进行巢友识别。我们利用不同蚁群之间表皮化合物的自然差异，来研究可能导致观察到的攻击行为中等级差异的近因。我们推断，大型工蚁与中型工蚁在攻击入侵者的总体倾向（巢友识别系统的“行动成分”）上存在差异，而小型工蚁似乎对外来气味不太敏感（“感知成分”）。我们的结果突出了社会性昆虫行为背后近因机制的重要性，并鼓励在分析诸如巢穴防御等群体水平特征时，重视群体内部的差异。
