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Solitary bees reduce investment in communication compared with their social relatives
Edited by Raghavendra Gadagkar, Indian Institute of Science, Bangalore, India, and approved April 26, 2017 (received for review December 19, 2016)

Significance
Communication is central to group living: Individuals use signals to identify each other and coordinate tasks. Surprisingly, little is known about how these communication systems change as social behavior evolves, particularly during the transition between solitary and group living. This study shows that, as sociality is gained and lost in halictid bees, convergent changes arise in the sensory systems and chemical signals of these groups. Solitary species show a repeated reduction of hair-like sensilla on the antennae, and social and solitary forms of the same species differ in their chemical signals. These results suggest that changes in group complexity are closely linked to changes in communication and that social bees invest more in these systems than their solitary counterparts.
Abstract
Social animals must communicate to define group membership and coordinate social organization. For social insects, communication is predominantly mediated through chemical signals, and as social complexity increases, so does the requirement for a greater diversity of signals. This relationship is particularly true for advanced eusocial insects, including ants, bees, and wasps, whose chemical communication systems have been well-characterized. However, we know surprisingly little about how these communication systems evolve during the transition between solitary and group living. Here, we demonstrate that the sensory systems associated with signal perception are evolutionarily labile. In particular, we show that differences in signal production and perception are tightly associated with changes in social behavior in halictid bees. Our results suggest that social species require a greater investment in communication than their solitary counterparts and that species that have reverted from eusociality to solitary living have repeatedly reduced investment in these potentially costly sensory perception systems.
Footnotes
- ↵1To whom correspondence should be addressed. Email: skocher{at}gmail.com.
Author contributions: B.W., M.A.E., N.E.P., and S.D.K. designed research; B.W., A.H., T.S., L.E.K.M., and S.D.K. performed research; B.W., A.H., and S.D.K. analyzed data; and B.W., M.A.E., N.E.P., and S.D.K. wrote the paper.
The authors declare no conflict of interest.
This article is a PNAS Direct Submission.
See Commentary on page 6424.
This article contains supporting information online at www.pnas.org/lookup/suppl/doi:10.1073/pnas.1620780114/-/DCSupplemental.
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