Eusocial Evolution in Termites and Hymenoptera

The evolution of eusociality remains an intriguing mystery. Why do individuals forego their own reproduction to help others produce offspring? Complex colonies have evolved in ants, bees, and wasps (Hymenoptera) and in termites (Isoptera). We discuss theories applied to explain eusocial traits in the Isoptera and the Hymenoptera in order to learn more about how and why eusociality evolved from subsocial ancestors. Striking overlap occurs in the genes controlling caste and the shift of parental care to offspring via heterochrony, suggesting ecological pressures lead to co-option of similar developmental mechanisms. There is also overlap in factors that predispose groups to eusociality, including extended parental care, defense of and the inheritance of a valuable nest, and enhanced direct and indirect benefits from cooperative behavior. However, differences in developmental paths and ecological traits are also informative, such as the evolution of the soldier form and adult workers. Multiple selective processes may favor eusociality over alternatives, but the degree to which each process was involved in eusocial evolution may have varied in each taxon. Reduced emphasis on haplodiploidy to explain eusocial evolution in the Hymenoptera and the similarities in developmental control allow for greater overlap of theories explaining eusocial evolution in the Hymenoptera and Isoptera.