Transmission Dynamics Of Parasitic Infections In Spatially Heterogeneous Environment

Parasitic infection plays an important role in ecosystems.Parasites can regular the dynamics of host populations,and can affect significantly species interactions as well as stability of ecological systems.Moreover,habitat loss and spatial clustering of lost patches are one of the key factors for species extinction.Here,we have explored effects of transmission path and trade-offs on disease dynamics and virulence evolution under spatially heterogeneous environment.In the thesis we have mainly discussed five chapters.In Chapter 1,we summarize the concept,theory and research status of parasitic infection in spatial heterogeneous environment.In Chapter 2,the related theory and several simple models of infectious disease have been discussed.In Chapter 3,we have established an infectious disease model with spatial heterogeneity and have discussed the impacts of the transmission mode,i.e.,horizontal transmission and vertical transmission,on the disease invasion and transmission dynamics under spatially heterogeneous landscapes.In Chapter 4,based on the spatial heterogeneity of infectious disease models,we have explored the effects of various trade-off forms between virulence and reproduction rate of infected hosts on the evolution of parasitic virulence.In the last Chapter,we have illustrated the summary and outlook.According to simulations of spatial host-parasite model,we mainly obtained the following results:(1)The horizontal and vertical transmissions have asymmetric effects on host-parasitic population dynamics;(2)In the heterogeneous environment,the more fragmented landscape(high amount of habitat loss and/or low clustering of lost patches)can enhance the importance of vertical transmission in disease invasion;(3)In contrast to homogeneous landscape,the vertical transmission is even proved to be a determinant role in disease invasion as facing a severe habitat loss;(4)Spatially stochastic simulation predicts that the occupancy of host populations displays different responses to heterogeneous resource quality and habitat loss,which may be because the habitat patch with low resource quality can still hold the reproduction of host individuals;(5)Distinct trade-off forms between the fecundity of infected host and transmission rate of the disease lead to differences in evolutionarily stable(ES)virulence.