寄生入侵对循环竞争系统动态的影响

Effects of parasite invasion on the dynamics of cyclic competition

寄生感染能够通过调节宿主种群的种间竞争关系影响种群动态,进而干扰整个竞争群落的稳定性与物种多样性。通过构建寄生物种干扰下的循环竞争系统,探讨不同时间尺度上的种群动态与物种续存对寄生特征的响应机制。模拟结果显示,寄生物种的入侵是影响循环竞争系统不稳定性的重要驱动因素之一。首先,寄生的入侵能够显著改变种群周期振荡模式,导致寄生调节的竞争系统在大时间尺度上呈现群落水平上的周期振荡,小时间尺度上呈现单种群的周期振荡。同时,种群生物量的时间序列自相关性和偏自相关性分析显示,大时间尺度上的群落周期振荡和小时间尺度上的种群周期振荡动态均是平稳的时间序列。其次,寄生入侵可导致阶段性平衡动态下的两物种灭绝,续存单物种的周期振荡动态,而局部稳定状态下,寄生入侵可引起循环竞争系统中三物种呈现完全一致的周期性振荡。同时,寄生循环竞争系统在达到平稳的过程中,产生生态系统中的瞬时动态行为,即两种动力学行为上突然转变的现象。此外,寄生物种的三个主要特征参数(传播率,脱落率以及致死率)均被证实能够改变大时间尺度或小时间尺度上的周期大小以及对应的物种丰富度。总之,寄生物种的入侵能够显著地改变竞争群落的稳定性与物种多样性,具有一定的研究意义。

Parasite can alter the dynamics and diversity of competitive communities indirectly.Here,we firstly constructed a cyclic competition system with three species mediated by a free-living parasite.Subsequently,we explored the effects of parasite traits on the transient dynamics of three host species,as well as the stability and species richness of the competitive community at different time-scales.Simulation results reveal that the invasion of parasite is a key factor in inducing the community unstability.Parasite traits and interspecific competition are likely crucial in structuring communities and disease dynamics.In particularly,parasite invasion can transform the classically periodic oscillation of cyclic community into more complex dynamics,such as periodic oscillation of the community at a large time scale,and periodic oscillation of a single species at a small time scale.Additionally,analysis of the autocorrelation function and partial autocorrelation function analysis for time series of species’biomass in the cyclic competition system indicate that the time series of species’biomass at both large and small time scales are stationary.Furthermore,as parasites invade the initial stage equilibrium dynamics of cyclic competition system,pathogenic infection can induce to the extinction of two species,leaving only one species to persist and undergo periodic oscillation.In cases of initial local stability,pathogenic infection can cause all three species to undergo periodic oscillation coincidently.Moreover,the observed transient dynamics of cyclic communities,including the timing of sudden switches in dynamics and other characteristics of transients,occur during the process of parasite invasion.Finally,three parasite traits(transmission rate,shedding rate and virulence)can alter the periodicity and corresponding species richness of cyclic competition.In short,parasite invasion can dramatically change community stability and species diversity.