Hõrak P, Saks L, Karu U, Ots I
Institute of Zoology and Hydrobiology, Tartu University, Tartu, Estonia.
J Evol Biol. 2006 Jan;19(1):277-88. doi: 10.1111/j.1420-9101.2005.00988.x.
The question why different host individuals within a population differ with respect to infection resistance is of fundamental importance for understanding the mechanisms of parasite-mediated selection. We addressed this question by infecting wild-caught captive male greenfinches with intestinal coccidian parasites originating either from single or multiple hosts. Birds with naturally low pre-experimental infection retained their low infection status also after reinfection with multiple strains, indicating that natural infection intensities confer information about the phenotypic ability of individuals to resist novel strains. Exposure to novel strains did not result in protective immunity against the subsequent infection with the same strains. Infection with multiple strains resulted in greater virulence than single-strain infection, indicating that parasites originating from different host individuals are genetically diverse. Our experiment thus demonstrates the validity of important but rarely tested assumptions of many models of parasite-mediated selection in a wild bird species and its common parasite.
在一个种群中,不同宿主个体在感染抗性方面存在差异的原因,对于理解寄生虫介导的选择机制至关重要。我们通过用源自单个或多个宿主的肠道球虫寄生虫感染野生捕获的圈养雄性绿翅雀来解决这个问题。实验前自然感染率低的鸟类在再次感染多种菌株后仍保持低感染状态,这表明自然感染强度提供了有关个体抵抗新菌株表型能力的信息。接触新菌株并未产生针对随后感染相同菌株的保护性免疫。感染多种菌株比单菌株感染导致更大的毒力,这表明源自不同宿主个体的寄生虫在基因上是多样的。因此,我们的实验证明了许多寄生虫介导的选择模型中重要但很少被检验的假设在一种野生鸟类及其常见寄生虫中的有效性。