Deciphering the genetic basis of hymenopteran social behavior

Since Darwin, biologists have been fascinated by the evolution of sociality. In its most extreme form, eusocial species exhibit a division of labor, with certain individuals performing reproductive tasks such as oviposition, while others perform non-reproductive roles such as foraging, nest building, and defense.

This type of system requires individuals to give up some or all of their own reproductive success to assist the reproduction of other individuals in the group. This is a concept that at first glance seems at odds with the main tenet of evolution: the driving force of natural selection on individuals. Although bees are perhaps the best-known social example, Racethe complex societies of honeybees, represents just one part of the range of social structures that can be observed in Hymenoptera, which includes bees, wasps and ants.

At the other end are the more rudimentary social structures, which at their most basic level involve the cooperation of just a few individuals and their descendants.Most of the previous research on insects sociability focus on more complex social systems, understanding the evolution of these more rudimentary forms may help reveal the earliest shifts in the path to sociality. .

The authors of a new study published in genome biology and evolution, We set out to fill this gap.

According to lead author Emeline Favreau, “Our study involved six bees and wasp species Although not highly social, they have more rudimentary forms of cooperation and are closely related to highly social species. ” by using machine learning algorithms to analyze gene expression The authors found a common genetic ‘toolkit’ for sociability that may form the basis for the evolution of more complex social structures across six species representing multiple origins of sociability.

The international team of researchers includes Katherine S. Geist (co-first authors) and Amy L. Toth from Iowa State University, Christopher DR Wyatt and Seilian Sumner from University College London, and Sandra M. Lehan from York University in Toronto. It was “The authors collaborated on this article because we believe it is important to understand the origins of sociability,” Favreau said.

“In the field, we observed a remarkable diversity of social life, including large nests of hornets busy in collective action, and small carpenter bees nesting in thin tree branches. In this paper, we We have delved deep into the evolutionary narrative and uncovered molecular evidence for the emergence of social organization.”

This study included a comparative meta-analysis of data from three wasp species and three wasp species representing four independent origins of sociability. Polystin wasps Polistes canadensis and P. dominula.

“Using data on global gene expression in the brains of different behavioral groups (breeding and non-breeding females), we are able to identify common genes associated with these basic social divisions in both honeybees and bees. We discovered that there is a core set,” explains Favreau. “This is exciting because it suggests that there may be common molecular ‘themes’ related to cross-species cooperation. ”

Many functional groups found to be related to sociability in this study are also related to sociability in other social bees and ants. These include genes associated with chromatin binding, DNA binding, regulation of telomere length, reproduction and metabolism.

On the other hand, this study also identified many lineage-specific genes and functional groups associated with social phenotypes. According to the authors, these findings “reveal how taxon-specific molecular mechanisms complement a core toolkit of molecular processes in shaping traits relevant to the evolution of eusociality.” ”.

Interestingly, Favreau said, “A machine learning approach to these large datasets was the best way to uncover these similarities.” The authors first tried traditional methods to study differential gene expression, but these largely grouped species by phylogeny and failed to identify gene sets associated with sociality. In contrast, machine learning tools offered a “more subtle and sensitive approach” that allowed the authors to identify similarities in gene expression over wide evolutionary distances.

One remaining question is that the results of this study, which focused on species with rudimentary forms of sociality, suggest that fully eusocial species, with morphologically distinct reproductive and non-reproductive castes, may not be fully eusocial. How can it be compared with other species? According to Favreau, “This is what we’re working on now and hopefully we’ll be able to address in the near future. We’ll see how genes and genomes change over the course of social evolution.” We’re taking a broader approach to find out.”

It includes additional transcriptomic data for 16 bee and wasp species, including “single, rudimentary and large-scale studies with complex sociopathic wasp and bee species. “Comparisonal research” becomes possible.

However, scaling up research requires obtaining samples from around the world, which has sometimes proven difficult. Some of them had never been studied before at the genetic level,” says Favreau.

“The global diversity of taxa and remote area Although many were collected, we are pleased to have obtained all specimens and genomes given the global pandemic and travel restrictions of the past few years. ”

The team was ultimately able to obtain a large number of samples through partnerships with other researchers and institutions, emphasizing the vital role of collaboration in scientific discovery.