ROLE SPECIALIZATION AND PLASTICITY AT THE ORIGIN OF EUSOCIALITY

一些个体为了帮助他人而放弃了自己的繁殖，这种进化代表了进化的重大转变之一。社会性的基本特征是劳动分工：蚁后是专门产蛋的，而工蚁则专门从事觅食等任务。许多有利于帮助的因素已经被识别出来，而且它的演变看起来似乎很简单。例如，雌性与兄弟姐妹的亲缘关系就像与自己后代的亲缘关系一样密切，这一事实可能表明，仅仅是相对于独立筑巢的微小优势就足以促进帮助的进化。然而，这意味着在优乐性的起源上存在着广泛的预先存在的可塑性，允许个人承担类似于今天的女王和工人的角色。在通常想象的情况下，突变的后代接管了幼崽的供养，将产卵权让给了母亲“女王”，后代的供养速度可能是独立育种者的两倍，母亲可能不得不产下两倍的卵，以避免选择支持祖先策略的女儿。如果专业化释放了不再用于履行一个角色的资源，但只有在职能之间存在高效的权衡时，才可能实现这一点。因此，一个关键的悬而未决的问题是，当分工最初演变时，它的效率会有多高。效率还需要宽容和反应能力：祖先的雌性会接受帮助者提供的食物，她们会相应地调整自己的喂养努力吗？专业化的回报可能取决于条件。一个长期存在的假设是，第一个帮助者是体型较小、生殖价值较低的雌性动物，帮助完全有生育能力的亲戚几乎没有什么损失。然而，提供或接受帮助对祖先女性的回报在多大程度上取决于表型仍不清楚。此外，亚育性假说的一个关键的未经检验的假设涉及体型较小/不育的雌性的觅食能力。这样的雌性在独立筑巢时繁殖力可能较低，但亚生育假说认为，它们会在提供食物等辅助任务中表现得更好。主要目标是首次使用大规模的对非社会性黄蜂Ammophila pubescens的现场操作：(1)测试角色专门化的好处：当非社会性雌性在实验中被迫专门化时，它们的产卵或提供能在多大程度上增加其终生产卵或供应？(2)测试亚育性假说的一个关键假设：通过专门化作为供应者，小雌性是否能获得最大收益？(3)测试是否存在互补的表型组合，双方可以通过筑巢获得好处(4)测试非社会性雌性对接受的耐受性和反应性对整体结果的帮助将是一个新的、令人兴奋的视角，即权衡和可塑性如何影响或约束共生社会的起源，这项工作将有益于昆虫学、进化生物学、行为生态学和动物行为学等多个学科的国际研究人员，包括理论家和经验学家，以及那些专门研究社会进化和动物社会进化的人。具体的研究重点很少被研究，因此，在新的方法和将产生的新数据方面，知识都有显著进步的潜力。群居昆虫的分工与细菌和藻类等其他类群之间存在有趣的相似之处。

The evolution of eusociality, where some individuals forfeit their own reproduction to help others, represents one of the major evolutionary transitions. The fundamental feature of eusociality is the division of labour: queens are specialist egg-layers while workers specialize on tasks such as foraging. Numerous factors that could favour helping have been identified, and its evolution can appear deceptively simple. For example, the fact that females are as closely related to their siblings as to their own offspring might suggest that just a tiny advantage over independent nesting will be enough to promote the evolution of helping. However, this implies that there was extensive pre-existing plasticity at the origin of eusociality, allowing individuals to take on roles similar to today's queens and workers. In the often-imagined scenario where a mutant offspring takes over brood provisioning, ceding egg-laying rights to a mother 'queen', the offspring could have to provision at twice the rate of an independent breeder, and the mother could have to lay twice as many eggs, to avoid selection on daughters favouring the ancestral strategy. This might be achieved if specialization frees up resources no longer utilized in performing one role, but only if there is a highly efficient trade-off between functions. A key unanswered question is therefore how efficient division of labour would be when it first evolved. Efficiency also requires tolerance and responsiveness: would ancestral females accept provisions provided by helpers, and would they adjust their own feeding effort accordingly?The payoff through specialization could be condition-dependent. A long-standing hypothesis is that the first helpers were small females with low reproductive value that forfeited little by helping a fully fertile relative. However, the extent to which payoffs to ancestral females from providing or receiving help depend on phenotype remains unclear. Furthermore, a critical untested assumption of the subfertility hypothesis concerns the foraging ability of small/subfertile females. Such females may have low fecundity when nesting independently, but the subfertility hypothesis assumes that they will perform better with helper tasks such as provisioning. Key objectives are to use large-scale field manipulations of the well studied non-social wasp Ammophila pubescens to for the first time: (1) Test the benefits of role specialization: to what extent can non-social females increase their lifetime egg-laying or provisioning when forced experimentally to specialize? (2) Test a key assumption of the subfertility hypothesis: do small females have the most to gain through specializing as provisioners? (3) Test whether there are complementary phenotype combinations where both parties could gain by nesting together (4) Test the tolerance and responsiveness of non-social females to received help The overall result will be a new and exciting perspective on how trade-offs and plasticity could influence or constrain the origin of eusociality, with important implications for the magnitude of ecological and genetic advantages necessary for eusociality to be favoured by selection.The work will benefit the international community of researchers in a variety of disciplines such as entomology, evolutionary biology, behavioural ecology and animal behaviour, including both theoreticians and empiricists, as well as those working specifically on social evolution and the evolution of animal societies. The specific research focus has been little studied, so that there is potential for a significant advancement of knowledge, in terms of both the novel approach and the new data that will be generated. There are interesting parallels between the division of labour in social insects and other taxa such as bacteria and algae.