Alteration of the Microbiome is Associated with Changes in Mating and Locomotion in Callosobruchus maculatus.

The seed beetle Callosobruchus maculatus is a model organism used to study environmental and genetic factors in the evolution of mating behaviors and life history traits. We sought to address the hypothesis that the microbiome of C. maculatus is associated with host life history traits and mating. To manipulate the microbiome, we developed a chemical treatment protocol to surface sterilize C. maculatus eggs and the food source on which they develop and examined the effect on microbial community structure, beetle life history traits, and mating behaviors including mate choice, and locomotion. Treatment eliminated culturable bacteria from the surface and altered the emerged adult beetle microbiome such that diversity was reduced and the community structure was altered. Treatment reduced survival of small male and female beetles; among the adults that did survive and emerge, females had higher fecundity compared to controls. We found that the treatment also affected mating behavior. Treated beetle pairs had a higher percentage of successful matings and a shorter mating latency period than control beetles. In mate choice tests in which a female was presented with either a treated or control male, females were more likely to mate with treated males. Finally, treated beetles exhibited increased locomotion. Treatment caused selective mortality of smaller individuals and reduced the diversity and altered the structure of the whole-body microbiome of the surviving adults. The treatment was also associated with enhanced mating behavior, increased fecundity and increased locomotion. These experiments revealed that treatment-induced perturbations in larvae result in altered adult behavior and life history traits that are associated with shifts in the beetle microbiome.