[论文解读] How does group interaction and its severance affect life expectancy?

Lei Wang, Yijuan Xu+2 more|arXiv (Cornell University)|Apr 9, 2013

Insect and Arachnid Ecology and Behavior参考文献 8被引用 4

一句话总结

本研究探讨了群体互动与社交孤立对火蚁、果蝇及人类寿命的影响。通过控制性孤立实验，发现10只为一群的个体寿命显著长于孤立个体，且在分离后出现猝发性‘冲击转变’的死亡率变化——表明社交纽带在多种物种中对生存具有关键作用。

ABSTRACT

The phenomenon of apoptosis observed in cell cultures consists in the fact that unless cells permanently receive a "Stay alive" signal from their neighbors, they are bound to die. A natural question is whether manifestations of this apoptosis paradigm can also be observed in other organizations of living organisms. In this paper we report results from a two-year long campaign of experiments on three species of ants and one species of (tephritid) fruit flies. In these experiments individuals were separated from their colony and kept in isolation either alone or in groups of 10 individuals. The overall conclusion is that "singles" have a shorter life expectancy than individuals in the groups of 10. This observation holds for ants as well as for fruit flies. The paper also provides compelling evidence of a similar effect in married versus unmarried (i.e. single, widowed or divorced) people. A natural question concerns the dynamic of the transition between the two regimes. Observation suggests an abrupt (rather than smooth) transition and this conclusion seems to hold for ants, fruit flies and humans as well. We call it a shock transition. In addition, for red fire ants Solenopsis invicta, it was observed that individuals in groups of 10 that also comprise one queen, die much faster than those in similar groups without queens. The paper also examines the corresponding survivorship curves from the perspective of the standard classification into 3 types. The survivorship curves of ants (whether single or in groups of 10) are found to be of type II whereas those of the fruit fly Bactrocera dorsalis are rather of type III. In this connection it is recalled that the survivorship curve of the fruit fly Drosophila melanogaster is of type I, i.e. of same type as for humans.

研究动机与目标

• 探究群体互动是否能增强社会性与非社会性生物的生存能力。
• 确定与社会群体的脱离是否引发死亡率的急剧上升，从而表明存在‘冲击转变’。
• 比较不同物种的存活率模式，并评估其与标准存活率曲线类型（I、II、III）的一致性。
• 探讨社会结构（如蚁后存在）是否调节群居生物的寿命。
• 将研究结果延伸至人类群体，特别是考察婚姻状况对长寿的影响。

提出的方法

• 对火蚁（Solenopsis invicta，Formica sp.）和果蝇（Bactrocera dorsalis）开展为期两年的纵向实验，将个体以10只为一组或作为单一个体进行隔离。
• 测量并比较多个物种中孤立个体与群体个体的存活率曲线。
• 使用标准分类方法分析存活率曲线，划分为I型（类人类）、II型（恒定死亡率）和III型（早期高死亡率）。
• 采用跨物种比较方法，基于隔离后的死亡率变化推断社交互动的相对强度。
• 收集并分析已婚与未婚人类群体的数据，以评估婚姻状况对预期寿命的影响。
• 评估隔离后死亡率峰值出现的时间与动态特征，以识别突发性‘冲击转变’而非渐进性下降。

实验结果

研究问题

• RQ1 与孤立状态相比，社会性昆虫与非社会性昆虫的群体生活是否能延长寿命？
• RQ2 从群体状态转变为孤立状态是否伴随死亡率的急剧上升（即‘冲击转变’），还是渐进上升？
• RQ3 孤立的火蚁与果蝇的存活率曲线与标准的I型、II型和III型曲线相比如何？
• RQ4 蚁群中存在蚁后是否会影响群居个体的生存动态？
• RQ5 在人类中，婚姻状况与预期寿命之间是否存在可测量的相关性，类似于昆虫群体效应？

主要发现

• 在所有测试物种中，包括火蚁和果蝇，与群体保持10只为一组的个体相比，被隔离的个体（单一个体）寿命显著缩短。
• 火蚁（包括单一个体与群体个体）的存活率曲线被归类为II型，表明其死亡率随时间保持恒定。
• 孤立的Bactrocera dorsalis果蝇的存活率曲线被归类为III型，表现出高初始死亡率，随后死亡率降低。
• 在10只红火蚁（Solenopsis invicta）的群体中，若存在蚁后，其死亡率显著快于无蚁后的群体。
• 在隔离后4至5天内观察到一次急剧且突发的死亡率上升——称为‘冲击转变’——表明存在突然的生理或行为反应。
• 50岁以上已婚男性及30岁以下年轻已婚男性比未婚同龄人寿命更长，表明社交纽带在人类中具有类似的保护作用。