Eawag, Aquatic Ecology, Dübendorf, Switzerland & IBZ, ETH-Zürich, Switzerland.
J Evol Biol. 2010 Nov;23(11):2370-6. doi: 10.1111/j.1420-9101.2010.02097.x. Epub 2010 Sep 6.
Natural populations often show genetic variation in parasite resistance, forming the basis for evolutionary response to selection imposed by parasitism. We investigated whether previous epidemics selected for higher resistance to novel parasite isolates in a Daphnia galeata-microparasite system by comparing susceptibility of host clones from populations with varying epidemic history. We manipulated resource availability to evaluate whether diet influences Daphnia susceptibility as epidemics are common in nutrient-rich lakes. Exposing clones from 10 lakes under two food treatments to an allopatric protozoan parasite, we found that Daphnia originating from lakes (mainly nutrient rich) with previous epidemics better resist infection. Despite this result, there was a tendency of higher susceptibility in the low food treatment, suggesting that higher resistance of clones from populations with epidemic background is not directly caused by lake nutrient level. Rather, our results imply that host populations respond to parasite-mediated selection by evolving higher parasite resistance.
自然种群中经常表现出寄生虫抗性的遗传变异，这为寄生虫寄生选择压力下的进化反应提供了基础。我们通过比较具有不同流行病史的宿主克隆的易感性，调查了先前的流行病是否选择了对新型寄生虫分离株更高的抗性，在一种 galeata 枝角类动物-微生物寄生虫系统中。我们操纵资源的可利用性，以评估饮食是否会影响枝角类动物的易感性，因为流行疾病在营养丰富的湖泊中很常见。我们将来自 10 个湖泊的克隆暴露于两种食物处理下的一种异域原生动物寄生虫中，发现来自先前流行疾病的湖泊（主要是营养丰富的湖泊）的枝角类动物更好地抵抗感染。尽管有这样的结果，但在低食物处理中存在更高易感性的趋势，这表明具有流行背景的种群的克隆的更高抗性不是直接由湖泊营养水平引起的。相反，我们的结果表明，宿主种群通过进化出更高的寄生虫抗性来应对寄生虫介导的选择。
