Reproductive concessions between related and unrelated members promote eusociality in bees.

Aline C R Andrade,Marco A Del Lama,Elder A Miranda,Fábio S Nascimento

doi:10.1038/srep26635

Aline C R Andrade, Marco A Del Lama + Show 2 more

Open Access

https://doi.org/10.1038/srep26635

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Abstract

Animal societies exhibit remarkable variation in their breeding strategies. Individuals can maximize their fitness by either reproducing or by helping relatives. Social hymenopterans have been key taxa for the study of Hamilton’s inclusive fitness theory because the haplodiploid sex-determination system results in asymmetric relatedness among breeders producing conflict over the partitioning of reproduction. In small cooperative groups of insects, totipotent individuals may maximize their inclusive fitness by controlling reproduction despotically rather than helping their relatives. Here, we demonstrate that the dominant females of the primitively eusocial bee Euglossa melanotricha (Apidae: Euglossini) control reproduction, but concede part of the reproductive output with their related and unrelated subordinates. As expected, a dominant female capitalizes on the direct reproduction of related subordinates, according to her interests. We found that reproductive skew was positively correlated with relatedness. The concessions were highly reduced in mother-daughter and sibling nests (relatedness r ± s.d. = 0.54 ± 0.02 and 0.79 ± 0.02, respectively) but much more egalitarian in unrelated associations (r = −0.10 ± 0.01). We concluded that reproductive skew in these primitively eusocial bees is strongly related to the genetic structure of associations, and also that females are able to assess pairwise relatedness, either directly or indirectly, and use this information to mediate social contracts.

Highlights

Animal societies exhibit remarkable variation in their breeding strategies
Our results demonstrate that the reproductive output of subordinates in E. melanotricha was affected by their degree of relatedness with the dominant female
The magnitude of the reproductive skew depended on the relatedness between group members

Summary

Introduction

Animal societies exhibit remarkable variation in their breeding strategies. Individuals can maximize their fitness by either reproducing or by helping relatives. As an unrelated subordinate lacks this indirect benefit of staying, the dominant female must grant her a share of direct reproduction to maintain the association (individuals can negotiate based on the threat of group dissolution - “outside option”)[8]. The reproductive dominance among females is determined by aggressive interactions and by egg removal (supplementary videos), which results in an age-based social hierarchy[11].

Results

Conclusion