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...不同生命功能（如繁殖活动）所分配的时间与能量之间的权衡，可因个体状态改变而触发——这类状态改变会削减可用资源，且通常由病原体、寄生虫等外源因素诱发。当个体受到病原体侵染时，它们可通过两种策略应对：要么以降低繁殖投入作为增强自身防御机制的代价，或是调整繁殖活动以提升繁殖力，从而尽可能降低过早死亡带来的适合度损失，这类行为符合终端投资假说（Terminal Investment Hypothesis, TIH）。该假说预测，未来繁殖可能性降低的个体，会最大化当前的繁殖投入，这可能包括调整繁殖时间节点。我们针对野生雌性成虫叩甲（Agriotes obscurus）暴露于真菌病原体布氏金龟子绿僵菌（Metarhizium brunneum）后的响应展开了研究。野外采集的叩甲个体中，暴露于高浓度M. brunneum的个体死亡时间更早，且死亡数量高于未暴露个体（原文至此截断）