Shrestha Sourya, Bjørnstad Ottar N, King Aaron A
Department of Ecology & Evolutionary Biology, University of Michigan, Ann Arbor, MI 48109, USA.
Department of Entomology and Biology, Pennsylvania State University, University Park, PA 16802, USA.
Theor Ecol. 2014 Aug 1;7(3):299-311. doi: 10.1007/s12080-014-0219-7.
Classical life-history theory predicts that acute, immunizing pathogens should maximize between-host transmission. When such pathogens induce violent epidemic outbreaks, however, a pathogen's short-term advantage at invasion may come at the expense of its ability to persist in the population over the long term. Here, we seek to understand how the classical and invasion-persistence trade-offs interact to shape pathogen life-history evolution as a function of the size and structure of the host population. We develop an individual-based infection model at three distinct levels of organization: within an individual host, among hosts within a local population, and among local populations within a metapopulation. We find a continuum of evolutionarily stable pathogen strategies. At one end of the spectrum-in large well-mixed populations-pathogens evolve to greater acuteness to maximize between-host transmission: the classical trade-off theory applies in this regime. At the other end of the spectrum-when the host population is broken into many small patches-selection favors less acute pathogens, which persist longer within a patch and thereby achieve enhanced between-patch transmission: the invasion-persistence tradeoff dominates in this regime. Between these extremes, we explore the effects of the size and structure of the host population in determining pathogen strategy. In general, pathogen strategies respond to evolutionary pressures arising at both scales.
经典的生活史理论预测，急性免疫病原体应使宿主间传播最大化。然而，当此类病原体引发剧烈的疫情爆发时，病原体在入侵时的短期优势可能会以其长期在种群中持续存在的能力为代价。在此，我们试图理解经典权衡与入侵 - 持久性权衡如何相互作用，从而根据宿主种群的规模和结构塑造病原体的生活史进化。我们在三个不同的组织层次上开发了一个基于个体的感染模型：在单个宿主体内、在当地种群中的宿主之间以及在集合种群中的当地种群之间。我们发现了一系列进化稳定的病原体策略。在频谱的一端——在大型充分混合的种群中——病原体进化得更加急性，以最大化宿主间传播：经典的权衡理论适用于这种情况。在频谱的另一端——当宿主种群被分成许多小斑块时——选择有利于不太急性的病原体，这些病原体在一个斑块内持续时间更长，从而实现斑块间传播的增强：入侵 - 持久性权衡在这种情况下占主导地位。在这些极端情况之间，我们探讨了宿主种群的规模和结构在决定病原体策略方面的影响。一般来说，病原体策略会对两个尺度上产生的进化压力做出反应。
