Spatial population genetic structure of a bacterial parasite in close coevolution with its host

Knowledge of a species’ population genetic structure can provide insight into fundamental ecological and evolutionary processes including gene flow, genetic drift, and adaptive evolution. Such inference is of particular importance for parasites, as an understanding of their population structure can illuminate epidemiological and coevolutionary dynamics. Here we describe the population genetic structure of the bacterium Pasteuria ramosa, a parasite that infects planktonic crustaceans of the genus Daphnia. This system has become a model for investigations of host-parasite interactions and represents an example of coevolution via negative frequency-dependent selection (a.k.a. ‘Red Queen’ dynamics). To sample P. ramosa, we experimentally infected a panel of Daphnia hosts with natural spore banks from the sediments of 25 ponds throughout much of the species range in Europe and Western Asia. Using 12 polymorphic VNTR loci, we identified substantial genetic diversity both within and among loca...解析物种种群的遗传结构，可为基因流（gene flow）、遗传漂变（genetic drift）与适应性进化（adaptive evolution）等核心生态与进化过程提供重要洞察。此类推断对于寄生生物而言尤为关键，因为明晰其种群结构能够阐明流行病学与共进化动态。本研究报道了枝芽孢杆菌（Pasteuria ramosa）的种群遗传结构——该寄生细菌可感染溞属（Daphnia）浮游甲壳动物。这一研究体系已成为宿主-寄生虫互作（host-parasite interactions）研究的经典模型，并代表了通过负频率依赖选择（negative frequency-dependent selection，又称"红皇后"动态）实现共进化的典型范例。为采集枝芽孢杆菌样本，我们利用覆盖该物种在欧洲与西亚的大部分分布范围的25个池塘沉积物中的自然孢子库，对一组溞属宿主开展了实验感染。借助12个多态可变数目串联重复序列（VNTR）位点，我们在采样地点内部及地点之间均检测到了显著的遗传多样性……