种群行为对疾病空间传播动态的影响

Effects of species behavior on the spatial dynamics of epidemic transmission

依据基于个体的空间模拟模型,文章构建了食饵感染疾病的一类捕食-食饵系统,并从特征调节的食饵偏好、寄生导致的宿主繁殖率下降以及捕食者对食饵资源的转换等方面研究种群行为的改变对疾病空间传播动态与生物控制的影响。其中,文章采用了无标度网络、小世界网络、随机网络以及规则格子等四种空间网络结构来明确网络异质性对疾病空间动态的影响。模拟结果显示,特征调节的捕食种群对食饵偏好的改变以及对食饵资源的转换行为显著影响了疾病的流行与捕食者的数量。不同网络结构下,疾病的流行与捕食者的数量之间均呈现显著的负相关性,这也说明捕食者对疾病的生物控制有不可忽视的作用;而寄生调节的宿主生长率对疾病的传播和捕食者数量产生较为微弱的影响。另外,空间网络拓扑结构的异质性对疾病的流行率也产生显著影响,网络结构异质性的增加将不利于局部感染作用的发生,从而抑制疾病的空间传播。最后,斑块发生率的模拟结果揭示,虽然网络节点的度越高越有利于局部相互作用的发生,但是已感染食饵为了权衡感染与捕食风险的正负作用,其斑块发生率呈现先增加后减弱的趋势。总之,种群的行为与网络空间结构的异质性均可作为控制疾病传播的有效策略,具有一定的研究意义。

Network structure and population behavior are two important factors affecting host dynamics and thus entail profound effects on spatial transmission of disease. Through the individual-based model, we here present a spatial model of a predator-prey/host-parasite system on four complex networks. Population behaviors are indicated by trait-mediated indirect effect on predator’s prey preference, parasite-induced reduction in reproduction rate and predator switching.Predator individuals can avoid infected ones and choose other susceptible host by switching effects. The significant difference of the four networks is their topological structures and heterogeneity. Results have shown that the spatial transmission of parasite on complex networks depends obviously on both the predator’s prey preference and predator switching. And parasite prevalence is always negatively correlated with predator abundance under the four various network structures. The result is consistent with previous studies and indicates that the enhanced predation pressure can impede the disease transmission. But parasite-induced reduction in reproduction rate has weak effects on the parasite prevalence and predator abundance. Meanwhile, the heterogeneity in network topological structures also influences the disease prevalence significantly. Parasite prevalence declines generally with the heterogeneity of the network, with scale-free networks having the lowest prevalence. Finally, we explore the mechanisms underlying such results by relating a node’s incidence with its degree. Because there are trade-offs between local infection and the predation interaction, the patch incidence of infected host increases firstly and then declines with its node’s degree. This work reveals that parasite transmission depends on both population behavior and the topology of networks. Therefore, the two factors can provide as the ecological strategy for controlling disease transmission.