Study Challenges Long-Held Belief on Insect Eusociality and Genetics

For over sixty years, scientists have debated whether a unique genetic system shared by ants, bees, and wasps has driven the evolution of eusociality, a sophisticated form of social organization. Eusociality involves colonies with reproductive division of labor, where queens reproduce and workers perform other roles. A new study from Arizona State University, published in Current Biology, suggests that genetics alone may not explain this complex social evolution.

The research indicates that while eusociality appears more frequently in insects with a haplodiploid genetic system, this pattern is largely due to the aculeate Hymenoptera group, which includes stinging wasps, bees, and ants. Haplodiploidy is a genetic system where females develop from fertilized eggs and have two chromosome sets, while males develop from unfertilized eggs with one set. This system was thought to make sisters more related to each other than to their offspring, potentially favoring cooperative behavior.

Lead author Sachin Suresh and senior author Timothy Linksvayer analyzed data from tens of thousands of insect species, using phylogenetic methods to assess the evolution of eusociality across different genetic systems. Their findings suggest that outside the aculeate Hymenoptera, haplodiploid insects do not develop eusociality more frequently than diploid insects, challenging the long-standing hypothesis.

The study examined nearly 69,000 insect species and found that the association between haplodiploidy and eusociality is not a universal rule but rather a result of specific evolutionary histories. This shifts the focus to other factors such as environmental conditions and life-history traits that may have facilitated the repeated emergence of complex insect societies.

This comprehensive analysis underscores the importance of using large datasets to revisit established theories in evolutionary biology, highlighting that traits like stingers and nesting behaviors may have played a significant role in the evolution of eusociality.