Files
Abstract
Social behavior and eusociality in particular are some of the most charismatic and well-studied phenomena in the order Hymenoptera. For decades, entomologists have described and analyzed insect sociality using whichever tools they had available at the time. Here I present a review and a series of studies that utilize modern, next-generation sequencing technologies in order to gain new perspectives on well-documented behaviors in two insect systems: the small carpenter bee Ceratina calcarata and the fire ant Solenopsis invicta. Ceratina calcarata exhibits a maternal care behavior, where a mother bee rears her offspring in a twig nest until they reach adulthood. We explored the behavioral, transcriptomic, and epigenetic effects that this maternal care has on developing offspring. We found many genes differentially expressed with the loss of maternal care as well as modest but significant changes in DNA methylation across the genome. Solenopsis invicta, being a fully eusocial ant, exhibits polymorphic castes and reproductive division of labor. These fire ants exhibit a social polymorphism in queen number with some colonies having single queens, others having multiple. This polymorphism also corresponds with morphological and behavioral differences between the colony types, all regulated by an inversion-based, Y-like supergene. We investigated the gene expression impacts of the supergene, first in gynes and then later in workers and males and identified a number of genes that appear to be central to the regulation of the complex phenotype of polygyny, including: OBP12, gas-8, and nrf-6. Further, we documented the complex gene regulatory landscape within the supergene that has led to the social polymorphism. These studies, taken together illustrate the distinct roles that gene regulatory evolutionary and gene family expansion have on the evolution and elaboration of complex social behaviors in the vicinity of archetypical eusociality.