School of Biological Sciences, Victoria University of Wellington, PO Box 600, Wellington, New Zealand.
Department of Animal Biology, University of Illinois, Urbana, Illinois, 61801, USA.
Ecology. 2017 Mar;98(3):861-874. doi: 10.1002/ecy.1714.
Biological invasions are a threat to global biodiversity and provide unique opportunities to study ecological processes. Population bottlenecks are a common feature of biological invasions and the severity of these bottlenecks is likely to be compounded as an invasive species spreads from initial invasion sites to additional locations. Despite extensive work on the genetic consequences of bottlenecks, we know little about how they influence microbial communities of the invaders themselves. Due to serial bottlenecks, invasive species may lose microbial symbionts including pathogenic taxa (the enemy release hypothesis) and/or may accumulate natural enemies with increasing time after invasion (the pathogen accumulation and invasive decline hypothesis). We tested these alternate hypotheses by surveying bacterial communities of Argentine ants (Linepithema humile). We found evidence for serial symbiont bottlenecks: the bacterial community richness declined over the invasion pathway from Argentina to New Zealand. The abundance of some genera, such as Lactobacillus, also significantly declined over the invasion pathway. Argentine ants from populations in the United States shared the most genera with ants from their native range in Argentina, while New Zealand shared the least (120 vs. 57, respectively). Nine genera were present in all sites around the globe possibly indicating a core group of obligate microbes. In accordance with the pathogen accumulation and invasive decline hypothesis, Argentine ants acquired genera unique to each specific invaded country. The United States had the most unique genera, though even within New Zealand these ants acquired symbionts. In addition to our biogeographic sampling, we administered antibiotics to Argentine ants to determine if changes in the micro-symbiont community could influence behavior and survival in interspecific interactions. Treatment with the antibiotics spectinomycin and kanamycin only slightly increased Argentine ant interspecific aggression, but this increase significantly decreased survival in interspecific interactions. The survival of the native ant species also decreased when the symbiotic microbial community within Argentine ants was modified by antibiotics. Our work offers support for both the enemy release hypothesis and that invasive species accumulate novel microbial taxa within their invaded range. These changes appear likely to influence invader behavior and survival.
生物入侵对全球生物多样性构成威胁，同时也为研究生态过程提供了独特的机会。种群瓶颈是生物入侵的一个常见特征，随着入侵物种从初始入侵地点传播到其他地点，这些瓶颈的严重程度可能会加剧。尽管人们对瓶颈的遗传后果进行了广泛的研究，但我们对它们如何影响入侵物种本身的微生物群落知之甚少。由于连续的瓶颈，入侵物种可能会失去微生物共生体，包括病原体分类群（敌人释放假说），或者随着入侵后时间的增加，可能会积累自然天敌（病原体积累和入侵衰退假说）。我们通过调查阿根廷蚂蚁（Linepithema humile）的细菌群落来检验这些替代假说。我们发现了连续共生体瓶颈的证据：细菌群落丰富度在从阿根廷到新西兰的入侵途径中下降。一些属的丰度，如乳酸杆菌，也在入侵途径中显著下降。来自美国种群的阿根廷蚂蚁与它们在阿根廷的原生范围的蚂蚁共享最多的属，而新西兰则共享最少（分别为 120 和 57）。九个属存在于全球所有地点，可能表明存在一个核心的必需微生物群。根据病原体积累和入侵衰退假说，阿根廷蚂蚁获得了每个特定入侵国家特有的属。美国拥有最多的特有属，尽管在新西兰，这些蚂蚁也获得了共生体。除了我们的生物地理采样，我们还对阿根廷蚂蚁使用抗生素，以确定微生物共生体群落的变化是否会影响种间相互作用中的行为和生存。用抗生素大观霉素和卡那霉素处理，仅略微增加了阿根廷蚂蚁的种间攻击性，但这种增加显著降低了种间相互作用中的生存能力。当用抗生素改变阿根廷蚂蚁体内共生微生物群落时，本地蚂蚁物种的生存能力也会下降。我们的工作为敌人释放假说和入侵物种在其入侵范围内积累新的微生物分类群提供了支持。这些变化可能会影响入侵物种的行为和生存。
