Data from: Discriminative host sanction together with relatedness promote the cooperation in fig/fig wasp mutualism

1. Sanctioning or punishing are regarded as one of most important dynamics in the evolution of cooperation. However, it has not been empirically examined yet whether or not such enforcement selection by sanctioning or punishing and classical theories like kin or reciprocity selection are separate mechanisms contributing to the evolution of cooperation. In addition, it remains largely unclear what factors determine the intensity or effectiveness of sanction. 2. Here we show that in the obligate, inter-specific cooperation between figs and fig wasps, the hosted figs can discriminatively sanction cheating individuals by decreasing the offspring development ratio. Concurrently, the figs can reward the cooperative pollinators with a higher offspring development ratio. This sanction intensity and effectiveness largely depend on how closely the host and symbiont are related either in terms of reciprocity exchange or genetic similarity as measured by the reciprocal of the foundress number. 3. Our results imply that in asymmetric systems, symbionts might be forced to evolve to be cooperative or even altruistic through discriminative sanction against the non-cooperative symbiont and reward to the cooperative symbiont by the host (i.e., through a game of “carrot and stick”).

1. 制裁与惩罚被视为合作演化进程中最为核心的驱动机制之一。然而，学界尚未通过实证检验明确：这类依托制裁或惩罚的强制选择，与亲缘选择（kin selection）、互惠选择（reciprocity selection）等经典理论所指代的演化机制，是否为独立作用于合作演化的不同驱动路径。此外，目前仍缺乏足够研究厘清哪些因素决定了制裁的强度与有效性。2. 本研究针对榕树与榕小蜂之间的专性种间合作体系展开分析，结果表明：宿主榕树可通过降低作弊个体的后代发育率，对其实施差异化制裁；与此同时，宿主榕树还可通过提升合作传粉者的后代发育率，对其给予奖励。该制裁的强度与有效性，主要取决于宿主与共生体（symbiont）之间的关联紧密程度——这种关联可从互惠交换或遗传相似性两个维度衡量，而遗传相似性可通过入驻榕果的雌蜂（foundress）数量的倒数进行量化。3. 本研究结果暗示，在不对称共生体系中，宿主可通过对非合作共生体实施差异化制裁、对合作共生体予以奖励的博弈策略（即“胡萝卜加大棒”策略），迫使共生体演化出合作行为，乃至利他行为。