从进化的角度来看,生命是关于繁殖。然而,在某些物种中,个人放弃自己的生殖来支持他人的生殖努力。例如,社会性昆虫群落,可以容纳多达一百万的工人,他们在觅食等任务中积极合作,育巢护理和筑巢防御,但不产生后代。在这样的社会中,劳动分工是明显的,繁殖仅限于一个或几个人,最著名的是女王。这种极端的社会组织仅存在于少数哺乳动物中,甲壳类动物和昆虫,但惊人的是,它按照膜翅目(包括蚂蚁,蜜蜂和黄蜂)。从孤独的生活方式到有组织的社会的转变可以通过自然选择发生,当帮助者从与亲属合作中获得健身益处时,由于通过兄弟姐妹间接传递基因。然而,这个过程,叫做亲属选择,容易受到无关个体的寄生和机会主义行为的影响。区分亲属和非亲属的能力,并做出相应的回应,因此,可以至关重要地促进Eusocity的发展和非生殖工作者的维护。因此,膜翅目大脑如何适应支持这一功能的问题是进化神经行为学中的一个基本问题。早期的神经解剖学研究表明,由于在处理社会信息的背景下选择了增强的认知能力,因此社会膜翅目已经扩大了综合大脑区域。后来的研究对这一假设提出了质疑,而是指出了高级社会组织与参与识别和交流的发达感觉结构之间的紧密联系。特别是,社会认同的化学信号,已知是通过表皮碳氢化合物(CHCs)介导的,可能与膜翅目中专门的化学感应系统携手进化。这里,我们在这个识别系统上编译当前的知识,从发出的身份信号中,化学检测的分子和神经元基础,特别强调它的进化史。最后,我们问膜翅目社会行为的演变是否可以推动其复杂嗅觉系统的扩展,或者专用于社会识别的嗅觉子系统的早期起源和保护是否可以解释该昆虫顺序中eusocial物种的丰度。回答这个问题将需要进一步的比较研究,以提供有关膜翅目嗅觉途径中谱系特异性适应的全面观点。
In evolutionary terms, life is about reproduction. Yet, in some species, individuals forgo their own reproduction to support the reproductive efforts of others. Social insect colonies for example, can contain up to a million workers that actively cooperate in tasks such as foraging, brood care and nest defence, but do not produce offspring. In such societies the division of labour is pronounced, and reproduction is restricted to just one or a few individuals, most notably the queen(s). This extreme eusocial organisation exists in only a few mammals, crustaceans and insects, but strikingly, it evolved independently up to nine times in the order Hymenoptera (including ants, bees and wasps). Transitions from a solitary lifestyle to an organised society can occur through natural selection when helpers obtain a fitness benefit from cooperating with kin, owing to the indirect transmission of genes through siblings. However, this process, called kin selection, is vulnerable to parasitism and opportunistic behaviours from unrelated individuals. An ability to distinguish kin from non-kin, and to respond accordingly, could therefore critically facilitate the evolution of eusociality and the maintenance of non-reproductive workers. The question of how the hymenopteran brain has adapted to support this function is therefore a fundamental issue in evolutionary neuroethology. Early neuroanatomical investigations proposed that social Hymenoptera have expanded integrative brain areas due to selection for increased cognitive capabilities in the context of processing social information. Later studies challenged this assumption and instead pointed to an intimate link between higher social organisation and the existence of developed sensory structures involved in recognition and communication. In particular, chemical signalling of social identity, known to be mediated through cuticular hydrocarbons (CHCs), may have evolved hand in hand with a specialised chemosensory system in Hymenoptera. Here, we compile the current knowledge on this recognition system, from emitted identity signals, to the molecular and neuronal basis of chemical detection, with particular emphasis on its evolutionary history. Finally, we ask whether the evolution of social behaviour in Hymenoptera could have driven the expansion of their complex olfactory system, or whether the early origin and conservation of an olfactory subsystem dedicated to social recognition could explain the abundance of eusocial species in this insect order. Answering this question will require further comparative studies to provide a comprehensive view on lineage-specific adaptations in the olfactory pathway of Hymenoptera.