Capaul Marc, Ebert Dieter
Zoologisches Institut, Universität Basel, Rheinsprung 9, 4051 Basel, Switzerland.
Evolution. 2003 Feb;57(2):249-60. doi: 10.1111/j.0014-3820.2003.tb00260.x.
It has been suggested that parasites are a strong selecting force for their hosts and therefore may alter the outcome of competition among host genotypes. We tested the extent to which parasite-mediated selection by different parasite species influenced competition among clones of the cyclic parthenogen Daphnia magna. We monitored clone frequency changes in laboratory microcosm populations consisting of 21 D. magna clones. Parasite treatments (two microsporidians, Glugoides intestinalis and Ordospora colligata) and a parasite-free control treatment were followed over a nine-month period. A further treatment with the bacterium Pasteuria ramosa failed. We found significant differences in clonal success among the treatments: the two parasite treatments differed from the control treatment and from each other. Additionally, we measured the clone-specific population carrying capacity, competitive ability against tester clones, and reproductive success of infected and uninfected females to test whether they correlate with clonal success in the microcosms. The clone-specific competitive ability was a good predictor of clonal success in the microcosms, but clonal carrying capacity and host reproductive success were not. Our study shows that parasite-mediated selection can strongly alter the outcome of clonal competition. The results suggest that parasites may influence microevolution in Daphnia populations during periods of asexual reproduction.
有人认为，寄生虫对其宿主是一种强大的选择力量，因此可能会改变宿主基因型之间的竞争结果。我们测试了不同寄生虫物种通过寄生虫介导的选择对周期性孤雌生殖的大型溞克隆之间竞争的影响程度。我们监测了由21个大型溞克隆组成的实验室微观种群中克隆频率的变化。在九个月的时间里，跟踪了寄生虫处理（两种微孢子虫，肠道格鲁吉亚虫和鄂尔多斯孢虫）以及无寄生虫的对照处理。用ramosa巴斯德氏菌进行的进一步处理失败了。我们发现各处理之间克隆成功率存在显著差异：两种寄生虫处理与对照处理不同，且彼此也不同。此外，我们测量了克隆特异性种群承载能力、对测试克隆的竞争能力以及受感染和未受感染雌性的繁殖成功率，以测试它们是否与微观世界中的克隆成功率相关。克隆特异性竞争能力是微观世界中克隆成功率的良好预测指标，但克隆承载能力和宿主繁殖成功率不是。我们的研究表明，寄生虫介导的选择可以强烈改变克隆竞争的结果。结果表明，寄生虫可能会在无性繁殖期间影响大型溞种群的微进化。
