KU Leuven, Interdisciplinary Research Facility Life Sciences, KULAK, Campus Kortrijk, Etienne Sabbelaan 53, Kortrijk, B-8500, Belgium.
Department of Computer Science, KU Leuven, Celestijnenlaan 200A, Leuven, B-3001, Belgium.
Ecology. 2017 Nov;98(11):2784-2798. doi: 10.1002/ecy.1994.
Changes in food quality can play a substantial role in the vulnerability of hosts to infectious diseases. In this study, we focused on the genetic differentiation of the water flea Daphnia magna towards food of different quality (by manipulating C:N:P ratios) and its impact on the interaction with a virulent infectious disease, "White Fat Cell Disease (WFCD)". Via a resurrection ecology approach, we isolated two Daphnia subpopulations from different depths in a sediment core, which were exposed to parasites and a nutrient ratio gradient in a common garden experiment. Our results showed a genetic basis for sensitivity towards food deprivation. Both fecundity and host survival was differently affected when fed with low-quality food. This strongly impacted the way both subpopulations interacted with this parasite. A historical reconstruction of nutrient changes in a sediment core reflected an increase in organic material and phosphorus concentration (more eutrophic conditions) over time in the studied pond. These results enable us to relate patterns of genetic differentiation in sensitivity towards food deprivation to an increasing level of eutrophication of the subpopulations, which ultimately impacts parasite virulence effects. This finding was confirmed via a dynamic energy budgets (DEB), in which energy was partitioned for the host and the parasite. The model was tailored to our study by integrating (1) increased growth and a fecundity shift in the host upon parasitism and (2) differences of food assimilation in the subpopulations showing that a reduced nutrient assimilation resulted in increased parasite virulence. The combination of our experiment with the DEB model shows that it is important to consider genetic diversity when studying the impact of nutritional stress on species interactions, especially in the context of changing environments and emerging infectious diseases.
食物质量的变化可能在宿主对传染病的易感性方面起着重要作用。在本研究中，我们专注于水蚤（Daphnia magna）对不同质量食物（通过操纵 C:N:P 比）的遗传分化及其对与一种致命传染病（“白脂肪细胞病（WFCD）”）相互作用的影响。通过复苏生态学方法，我们从沉积物核心的不同深度分离出两个水蚤亚种群，并在一个共同花园实验中使它们暴露于寄生虫和营养比梯度下。我们的研究结果表明，水蚤对食物匮乏的敏感性具有遗传基础。当喂食低质量食物时，繁殖力和宿主存活率都受到不同程度的影响。这强烈影响了两个亚种群与这种寄生虫相互作用的方式。沉积物核心中营养变化的历史重建反映了研究池塘中有机物质和磷浓度（富营养化条件）随时间的增加。这些结果使我们能够将对食物匮乏的敏感性的遗传分化模式与亚种群富营养化程度的增加联系起来，这最终会影响寄生虫的毒力效应。这一发现通过动态能量预算（DEB）得到了证实，其中能量在宿主和寄生虫之间进行了分配。该模型通过整合（1）寄生后宿主的生长和繁殖力增加以及（2）亚种群中食物同化的差异进行了调整，表明营养同化减少导致寄生虫毒力增加。我们的实验与 DEB 模型的结合表明，在研究营养压力对物种相互作用的影响时，特别是在环境变化和新发传染病的背景下，考虑遗传多样性非常重要。
