School of Biology and Ecology, University of Maine, Orono, Maine, United States of America.
PLoS One. 2021 May 10;16(5):e0251497. doi: 10.1371/journal.pone.0251497. eCollection 2021.
The blacklegged tick (Ixodes scapularis) and the invasive European fire ant (Myrmica rubra) are both expanding throughout their sympatric range in coastal New England. Ixodes scapularis is the primary vector of the bacterium Borrelia burgdorferi, which is the causative agent of Lyme disease, and Mount Desert Island, Maine, home to Acadia National Park, currently is affected by a high Lyme disease burden. Ticks have many natural predators, including ants, although no previous studies have investigated interactions between these two species. To test the hypothesis that the presence of M. rubra alters I. scapularis abundance, we collected ticks by drag-sampling at eight ant-infested sites and eight uninfested control sites in Acadia National Park. We found that nymph density was significantly higher at ant-infested sites, while larval density was significantly higher at control sites. In addition, we conducted a laboratory bioassay to measure M. rubra aggression against I. scapularis larvae, nymphs, and adults and Dermacentor variabilis adults, and found that ant aggression was significantly higher against D. variabilis adults than I. scapularis adults. Our findings support the hypothesis that M. rubra has divergent effects across I. scapularis life stages, and we discuss possible ecological mechanisms, including optimal microclimate and predation, that could promote density of nymphs while inhibiting density of larvae.
黑腿蜱（Ixodes scapularis）和入侵的欧洲红火蚁（Myrmica rubra）都在其新英格兰沿海的共生范围内扩张。黑腿蜱是伯氏疏螺旋体（Borrelia burgdorferi）的主要传播媒介，伯氏疏螺旋体是莱姆病的病原体，而缅因州的芒特迪瑟特岛（Mount Desert Island）是阿卡迪亚国家公园（Acadia National Park）的所在地，目前正受到莱姆病高负担的影响。蜱有许多天敌，包括蚂蚁，尽管以前没有研究调查过这两个物种之间的相互作用。为了检验红火蚁的存在是否会改变黑腿蜱的丰度的假设，我们在阿卡迪亚国家公园的 8 个蚂蚁滋生地和 8 个未受干扰的对照地用拖曳采样法收集了蜱。我们发现，在蚂蚁滋生地，若虫密度明显更高，而在对照地，幼虫密度明显更高。此外，我们进行了实验室生物测定，以测量红火蚁对黑腿蜱幼虫、若虫和成虫以及黑脚硬蜱（Dermacentor variabilis）成虫的攻击性，发现红火蚁对黑脚硬蜱成虫的攻击性明显高于黑腿蜱成虫。我们的发现支持了这样一种假设，即红火蚁对黑腿蜱的各个生命阶段有不同的影响，我们讨论了可能的生态机制，包括最佳微气候和捕食，这可能会促进若虫的密度，同时抑制幼虫的密度。
