Collective defence portfolios of ant hosts shift with social parasite pressure

Host defences become increasingly costly as parasites breach successive lines of defence. Because selection favours hosts that successfully resist parasitism at the lowest possible cost, escalating coevolutionary arms races are likely to drive host defence portfolios towards ever more expensive strategies. We investigated the interplay between host defence portfolios and social parasite pressure by comparing 17 populations of two Temnothorax ant species. When successful, collective aggression not only prevents parasitation but also spares host colonies the cost of searching for and moving to a new nest site. However, once parasites breach the host's nest defence, host colonies should resort to flight as the more beneficial resistance strategy. We show that under low parasite pressure, host colonies more likely responded to an intruding Protomognathus americanus slavemaker with collective aggression, which prevented the slavemaker from escaping and potentially recruiting nest-mates. Howe...当寄生虫依次突破宿主的各级防御防线时，宿主的防御成本会不断攀升。由于自然选择青睐以最低成本成功抵御寄生的宿主，持续升级的协同进化军备竞赛极有可能推动宿主的防御组合朝向愈发昂贵的防御策略演化。本研究通过对比两种扁胸切叶蚁（Temnothorax）的17个种群，探究了宿主防御组合与社会性寄生压力之间的相互作用。若集体御敌行为奏效，不仅可阻断寄生侵染，还能免除宿主蚁群寻找并迁移至新巢址的成本。但一旦寄生虫突破宿主的巢内防御，宿主蚁群则应转而采取逃迁策略，作为更具优势的防御手段。我们的研究结果表明，在寄生压力较低的环境中，宿主蚁群更倾向于以集体御敌行为应对入侵的美洲蓄奴蚁（Protomognathus americanus），此举可阻止该蓄奴蚁逃脱并招募同巢同伴。Howe...