Unrelated helpers in social wasps

社会性的进化是进化生物学的主要转变之一。关于帮助起源的理论的关键检验基础是原始的社会分类，在这些分类中仍然存在独立繁殖的选择。Polistes纸蜂的社会群体由一群雌性组成，其中一只“占主导地位”的雌性产卵大部分或全部，而其他(“助手”)则觅食该占主导地位的幼虫。然而，尽管Polistes是原始社会系统中研究得最好的，但我们仍然不清楚为什么许多女性选择成为帮手，而不是自己筑巢和独立繁殖。尤其矛盾的是，占优势的P.domulus的种群，其中30%的帮助者与群中的优势卵蛋无关。不相关的帮助者不能通过饲养优势种(近亲选择)的后代来间接传播他们的基因，因此必须试图通过自己产卵来获得直接的适合度。这项拟议的研究将使用大规模野外实验和基因工作相结合的方法来调查西班牙种群中无血缘关系的雌性种群的生殖策略。这项工作将：(1)估计不相关的母鹿的繁殖成功，特别关注通过产卵位置的遗传进行繁殖，这一路线在以前对原始社会性昆虫的研究中被明显忽视。(2)通过比较不相关的帮助者和作为支配者姐妹的帮助者在以下方面的影响来区分亲属选择的影响和直接健康利益：(I)帮助努力；(Ii)在队列中继承优势产卵地位的位置；(Iii)在未被操纵的群体中的攻击性；(Iv)在取代支配者的关键时刻的攻击性。总体结果将是对帮助原始群居昆虫的基础进行最全面的评估，并首次明确区分亲缘选择和直接健康益处如何影响个人行为。

The evolution of sociality is one of the major transitions in evolutionary biology. The key testing-grounds for theories concerning the origin of helping are primitively eusocial taxa in which the option of independent reproduction still exists. Social groups of Polistes paper wasps comprise groups of females in which one 'dominant' female lays most or all of the eggs while the others ( 'helpers') forage to feed the dominant's larvae. Yet despite Polistes being the best studied primitively eusocial system, it remains unclear why many females choose to become helpers rather than build their own nests and reproduce independently. Especially paradoxical are populations of P. dominulus, in which >30% of helpers are unrelated to the dominant egg-layer in the group. Unrelated helpers cannot transmit their genes indirectly by rearing offspring of the dominant (kin selection), and so must attempt to obtain direct fitness by laying eggs themselves. The proposed research will use a combination of large-scale field experiments and genetic work to investigate the reproductive strategies of unrelated females in a Spanish population of P. dominulus. The work will: (1) Estimate the reproductive success of unrelated foundresses, focussing particularly on reproduction through inheritance of the egg-laying position, a route that has been strikingly neglected in previous studies of primitively eusocial insects. (2) Separate the effects of kin selection and direct fitness benefits by comparing unrelated helpers with helpers that are sisters of the dominant in terms of: (i) helping effort; (ii) position in the queue to inherit the dominant egg-laying position; (iii) aggression in unmanipulated colonies; (iv) aggression at the critical moment when the dominant is replaced. The overall result will be the most comprehensive evaluation of the basis of helping in a primitively eusocial insect, and the first clear separation of how kin selection and direct fitness benefits influence individual behaviour.