Effects of Weather on Social Behavior in Forked Fungus Beetles

Science Center, Bent Corridor

Abiotic factors and the physical environment are known to mediate social interactions and behavior in many insects. An extreme instance of this effect is seen in sweat bees (Halictidae), where differences in sunlight and temperature affect whether bees of the same species adopt a solitary or eusocial lifestyle. On a smaller time scale, some beetles are known to alter their mating and social behavior in response to changes in temperature or barometric pressure. These effects have not been looked at in the forked fungus beetle (Bolitotherus cornutus), a mycophagous insect used as a study system to examine the role of social networks in phenotypic evolution. This project investigated the effects of climatic variables on social and mating behavior in twenty populations containing close to 1000 individuals total. For each observation period, temperature, air pressure, and humidity measurements were obtained and the time since last rain was calculated. As expected in ectotherms, temperature was strongly positively correlated with activity level, but also predicted lower levels of mating behavior and higher levels of non-mating social behavior. Higher air pressure, on the other hand, predicted lower levels of overall beetle activity but increased mating behavior. No weather factor was able to predict observed sex ratio in the populations, which was widely variable. These results point to social behavior influenced by an intersection of social and climatic elements, which should be considered in future evaluations of social networks to avoid confusing transient environmental effects with lasting network traits.