Understanding the evolution of eusociality, defined by distinct reproductive and nonreproductive castes, at the molecular level, has always been an essential and highly challenging topic of biology. Eusociality has evolved multiple times independently and involved many incremental steps, resulted in intermediate levels of social complexity. The Apinae (corbiculate bees) consists of 4 tribes with a wide range of social complexity: orchid bees (Euglossini), bumble bees (Bombini), stingless bees (Meliponini), and honey bees (Apini); is an ideal group for comparative studies of eusocial evolution in Hymenoptera. The first sequenced genome of the honey bee Apis mellifera in 2006 has become a gateway for numerous studies of corbiculate bees. However, most studies focused on only a relatively small taxa number and a narrow range of social lifestyle, which leads to a knowledge gap that has hindered our ability to understand what happens at the molecular level during this major evolutionary transition.
Previous studies revealed several exceptional traits of the Apini species genome, including a low but heterogeneous GC content with a bimodal distribution, the highest recombination rate among the metazoan. Because eusociality and high recombination rates may co-evolve, we suspect that the advanced eusocial lifestyle does contribute to the Apis mellifera GC content bimodality. Based on our current base compositional analysis on various Hymenoptera insects, we have found evidence that the bimodal GC content distribution is profound in the Apini tribe bees and is not a universal trait of eusociality. We hypothesize these differences in genomic base composition are associated with the social complexity level and evolution of eusociality in corbiculate bees. Therefore, this project’s main objective is to elucidate the evolutionary forces that shape genomic base composition in the eusocial corbiculate bees genome. We are proposing to accomplish this goal with the following aims: 1) Investigate the mutation of corbiculate bees and gain better insight into the mutation rate between different social level bees; 2) Estimate the recombination rate of eusocial corbiculate bees; 3) Resolve the origin of advanced eusociality in corbiculate bees.
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