Impact of heat stress on colony foundation in ants

Climate change not only leads to increased average temperatures but also to episodes of extreme heat that impact the reproduction and survival of organisms. These effects have broader ecological consequences when thermal disturbances affect ecosystem engineers such as ants. The impacts of thermal stress on ant populations have primarily been studied in mature colonies, which are relatively protected against thermal disturbances by the nest architecture and/or various behavioural responses. However, little is known about the effects of thermal stress on founding queens, which are commonly exposed to heat stress during and after the nuptial flight. To study this question, we exposed founding queens of the black garden ant (Lasius niger) to a brief, acute heat stress just after the nuptial flight. We then monitored queen survival and the number of eggs, larvae, pupae and workers produced. We found that the exposure of founding queens to the thermal stress impacted the success of colony foundation via increased queen mortality and reduced likelihood of producing workers, which primarily stemmed from alterations of egg production and/or development. Our results demonstrate the impact of thermal disturbances associated with climate change on the foundation of ant colonies, which could lead to declines in ant populations.