U.S. Forest Service Northern Research Station, 180 Canfield Street, Morgantown, West Virginia 26505, USA.
Ecology. 2013 Jun;94(6):1217-22. doi: 10.1890/12-1329.1.
Population cycles in forest Lepidoptera often result from recurring density-dependent epizootics of entomopathogens. While these systems are typically dominated by a single pathogen species, insects are often infected by multiple pathogens, yet little is known how pathogens interact to affect host dynamics. The apparent invasion of northeastern North America by the fungal entomopathogen Entomophaga maimaiga some time prior to 1989 provides a unique opportunity to evaluate such interactions. Prior to the arrival of E. maimaga, the oscillatory dynamics of host gypsy moth, Lymantria dispar, populations were apparently driven by epizootics of a nucleopolyhedrovirus. Subsequent to its emergence, E. maimaiga has caused extensive mortality in host populations, but little is known about how it has altered multigenerational dynamics of the gypsy moth and its virus. Here we compared demographic data collected in gypsy moth populations prior to vs. after E. maimaiga's invasion. We found that the recently invading fungal pathogen virtually always causes greater levels of mortality in hosts than does the virus, but fungal mortality is largely density independent. Moreover, the presence of the fungus has apparently not altered the gypsy moth-virus density-dependent interactions that were shown to drive periodic oscillations in hosts before the arrival of the fungus.
森林鳞翅目昆虫的种群周期通常是由反复发生的、依赖密度的昆虫病原物流行病引起的。虽然这些系统通常由单一的病原体物种主导，但昆虫通常会被多种病原体感染，但人们对病原体如何相互作用影响宿主动态知之甚少。真菌性昆虫病原物嗜虫霉属在 1989 年之前侵入美国东北部，为评估这种相互作用提供了一个独特的机会。在嗜虫霉属到来之前，舞毒蛾宿主的振荡动态显然是由核多角体病毒的流行病驱动的。在它出现之后，嗜虫霉属导致了宿主舞毒蛾种群的大量死亡，但人们对它如何改变舞毒蛾及其病毒的多代动态知之甚少。在这里，我们比较了在嗜虫霉属入侵前后收集的舞毒蛾种群的人口数据。我们发现，最近入侵的真菌病原体几乎总是在宿主中引起比病毒更高水平的死亡率，但真菌死亡率在很大程度上是与密度无关的。此外，真菌的存在显然没有改变舞毒蛾-病毒的密度依赖相互作用，这种相互作用在真菌到达之前被证明是导致宿主周期性振荡的原因。
