Data from: Parasites driving host diversity: incidence of disease correlated with Daphnia clonal turnover

According to the Red Queen hypothesis, clonal diversity in asexual populations could be maintained by negative frequency-dependant selection by co-evolving parasites. If common clones are selected against and rare clones gain a concomitant advantage, we expect that clonal turnover should be faster during parasite epidemics than between them. We tested this hypothesis exploring field data of the Daphnia – Caullerya host-parasite system. The clonal make-up and turnover of the Daphnia host population was tracked with high temporal resolution from 1998 until 2013, using first allozyme markers and later microsatellite markers. Significant differences in the clonal composition between random and infected sub-samples of Daphnia populations were detected on six of seven tested occasions, confirming genetic specificity of the host-parasite interaction in this system. We used time series analysis to compare the rates of host clonal turnover to the incidence of parasitism, and found that Caullerya prevalence was significantly associated with microsatellite-based clonal turnover. As alternate hypotheses, we further tested whether turnover was related to a variety of biotic, abiotic, and host demographic parameters. Other significant correlates of turnover were cyanobacterial biomass and (weakly) temperature. Overall, parasitism seems to be a strong driver of host clonal turnover, in support of the Red Queen hypothesis.

根据红皇后假说（Red Queen hypothesis），协同进化的寄生虫可通过负频率依赖选择（negative frequency-dependent selection）维持无性繁殖种群的克隆多样性。若常见克隆受到负向选择，而稀有克隆获得相应生存优势，则可预期：寄生虫流行期间的克隆更替率（clonal turnover）应快于非流行阶段。
我们以蚤状溞（Daphnia）- 凯伦虫（Caullerya）宿主-寄生虫系统的野外观测数据为基础，对该假说展开验证。
1998年至2013年间，研究团队先后采用同工酶标记（allozyme markers）与微卫星标记（microsatellite markers），以高时间分辨率追踪了宿主蚤状溞种群的克隆组成与更替动态。在7次检测中，有6次检测到蚤状溞种群的随机采样分组与感染采样分组的克隆组成存在显著差异，证实了该系统中宿主与寄生虫互作的遗传特异性。
我们通过时间序列分析（time series analysis）对比了宿主克隆更替率与寄生虫感染发生率，发现凯伦虫的感染率与基于微卫星标记的克隆更替率显著相关。
作为备择假说，我们进一步检验了克隆更替与各类生物、非生物及宿主种群统计参数的关联，结果显示克隆更替的其他显著关联因素包括蓝藻生物量，以及（弱相关的）环境温度。
整体而言，寄生虫感染是驱动宿主克隆更替的关键因素，这一发现支持红皇后假说。