Abstract

How mutual tolerance is produced, and the role of social environment in inducing cooperation in social groups, remains unstudied in many simple societies. In particular, maternal and sibling care and conflict are challenging to manipulate experimentally for many species. Most bees are solitary, but mothers of the eastern small carpenter bee, Ceratina calcarata, engage in prolonged care of offspring, and are therefore subsocial. Females form social associations of parents and a single generation of offspring, including a smaller dwarf eldest daughter (DED) who forages and feeds her adult siblings. Adult assemblages of C. calcarata present a unique opportunity to study the effect of social environment on cooperation and sibling care in an otherwise subsocial bee. To study how social environment influences foraging and intranidal behaviors, observation nests were constructed, and unaltered as a control, or treated by removing either only mothers or both mothers and DEDs. Nests were video-recorded for 464 h during summer (July–August) parent-adult offspring cohabitation. Individual and interactive behaviors were scored. In the absence of mothers, offspring were more tolerant, suggesting that a hierarchy between mother and offspring produces less tolerance between offspring. Aggression was only significantly greater in the absence of both mother and DED. We found that foraging was the lowest in the absence of mothers, and persisted in the absence of both mother and DED. This study provides the first detailed account of the intranidal behaviors of this species and experimentally reveals how social environment influences cooperative behavior.

Significance statement

Understanding how particular life histories, such as extended parental care, may set the stage for more complex social behaviors, such as sibling cooperation, is critical to understanding how alloparental care evolves in group living organisms. Most species exhibiting parental care and sibling cooperation are difficult to manipulate experimentally. Though relatively uncommon in invertebrates, extended parental care is frequently found in small carpenter bees that can be carefully observed within their nests and foraging. Here, we examine how the absence of mothers and worker-like daughters influences the social behavior of related adults living in close group association of such bees. This experiment presents an intranidal study of a subsocial bee’s behavior, and our results suggest that mothers play a dramatic role regulating social behavior. Furthermore, our results show that siblings are more tolerant in the absence of mothers, suggesting that mothers may maintain social hierarchies among offspring. Siblings may interact more aggressively and more frequently as they negotiate intranidal and foraging tasks in the absence of maternal care.

中文翻译：

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社会环境对初期社会蜜蜂Ceratina calcarata中合作与冲突的影响

摘要

在许多简单的社会中，仍未研究如何产生相互宽容，以及社会环境在诱导社会团体合作中的作用。特别是，对许多物种进行实验性操纵时，孕产妇和兄弟姐妹的照顾与冲突是具有挑战性的。大多数蜜蜂是独居的，但东部小木匠蜜蜂Ceratina calcarata的母亲从事后代的长期照料，因此是近社会的。女性由父母和单代后代组成社会协会，其中包括一个较小的矮人长女（DED），后者觅食和喂养其成年兄弟姐妹。C. calcarata的成年组合提供了一个独特的机会来研究社会环境对其他亚社会蜜蜂中合作与兄弟姐妹护理的影响。为了研究社会环境如何影响觅食和内部行为，建造了观察巢，将其保留下来作为对照，或者仅移走母亲，或者只移走母亲和DED来对其进行治疗。在夏季（7月至8月）父母-成年子女同居的过程中，对巢进行了464小时的录像。对个人和互动行为进行评分。在没有母亲的情况下，后代的耐受性更高，这表明母亲和后代之间的等级制对后代的耐受性较低。只有在没有母亲和DED的情况下，侵略性才明显更大。我们发现，在没有母亲的情况下觅食是最低的，而在没有母亲和DED的情况下觅食却持续存在。

重要性声明

了解特殊的生活史，例如扩展的父母照料，可能会为更复杂的社会行为（例如同胞合作）奠定基础，这对于理解同代父母照料如何在集体生活的生物体中发展至关重要。大多数表现出父母关怀和同胞合作的物种很难通过实验来操纵。尽管在无脊椎动物中相对较少见，但在小木匠蜜蜂中经常发现扩展的父母照顾，可以在它们的巢穴和觅食中对其进行仔细观察。在这里，我们研究了缺少母亲和像工人们的女儿如何影响生活在这种蜜蜂的紧密团体中的相关成年人的社会行为。该实验提出了对亚社会蜜蜂行为的内部调查研究，我们的结果表明，母亲在调节社会行为方面起着戏剧性的作用。此外，我们的研究结果表明，在没有母亲的情况下，兄弟姐妹更加宽容，这表明母亲可能在后代中保持社会等级制度。在没有孕产妇护理的情况下，兄弟姐妹可能会更积极，更频繁地进行交往，因为他们在谈判下进行内部和觅食任务。