Modification of reproductive schedule in response to pathogen exposure in a wild insect: support for the terminal investment hypothesis

Trade-offs in the time and energy allocated to different functions, such as reproductive activities, can be driven by alterations in condition which reduce resources, often in response to extrinsic factors such as pathogens or parasites. When individuals are challenged by a pathogen they may either reduce reproduction as a cost of increasing defence mechanisms, or alternatively, modify reproductive activities so as to increase fecundity thereby minimizing the fitness costs of earlier death, a behaviour consistent with the terminal investment hypothesis (TIH). The TIH predicts that individuals with decreased likelihood of future reproduction will maximize current reproductive effort, which may include shifts in reproductive timing. We examined how wild, adult female click beetles (Agriotes obscurus) responded after exposure to the fungal pathogenMetarhizium brunneum. Field-collected beetles exposed to a high concentration of M. brunneum died earlier and in greater numbers than those expo...