Data from: Convergent reversion to single mating in a wasp social parasite

While eusociality arose in species with single-mating females, multiple mating by queens has evolved repeatedly across the social ants, bees, and wasps. Understanding the benefits and costs of multiple mating of queens is important because polyandry results in reduced relatedness between siblings, reducing kin-selected benefits of helping while also selecting for secondary social traits that reduce intracolony conflict. The leading hypothesis for the benefits of polyandry in social insects emphasizes advantages of a genetically diverse workforce. Workerless social parasite species (inquilines) provide a unique opportunity to test this hypothesis, since they are derived from social ancestors but do not produce workers of their own. Such parasites are thus predicted to evolve single mating because they would experience the costs of multiple mating but not the benefits if such benefits accrue through the production of a genetically diverse group of workers. Here we show that the workerless social parasite Dolichovespula arctica, a derived parasite of wasps, has reverted to obligate single mating from a facultatively polyandrous ancestor, mirroring a similar reversion from obligate polyandry to approximate monandry in a social parasite of fungus-farming ants. This finding and a comparison with two other cases where inquilinism did not induce reversal to monandry support the hypothesis that facultative polyandry can be costly and may be maintained by benefits of a genetically diverse workforce.尽管真社会性（eusociality）起源于雌性单配的物种，但蚁后多次交配的现象在社会性蚂蚁、蜜蜂与胡蜂类群中反复独立演化。阐明蚁后多配的收益与成本具有重要意义：一妻多夫制（polyandry）会降低同胞间的亲缘关系，削弱基于亲缘选择的利他行为收益，同时还会筛选出可降低群体内冲突的次级社会性状。针对社会性昆虫多配收益的主流假说，核心强调遗传多样的劳动群体所带来的优势。无工虫的社会性寄生物（inquilines）为验证该假说提供了独特契机——这类寄生物源自社会性祖先类群，自身却无法产生工虫。因此理论预测，这类寄生物应演化出专性单配行为：若多配的收益源于遗传多样的工虫群体，那么这类寄生物仅会承担多配的成本，却无法获得相应收益。本研究发现，无工虫的社会性寄生物——胡蜂科的Dolichovespula arctica（一种衍生型胡蜂寄生物），已从兼性一妻多夫的祖先类群逆转至专性单配，这与真菌种植蚁的社会性寄生物从专性多配逆转至近似单配的现象相呼应。结合另外两例社会寄生并未引发单配逆转的案例进行对比，本研究结果支持以下假说：兼性一妻多夫制存在演化成本，其得以维持的原因正是遗传多样的劳动群体所带来的收益。