扬州大学生物数学讨论班

2017年6月3日8：30

数学科学学院报告厅

报告题目与摘要

报告人：Magnus Lindh瑞典龙德大学

报告题目：Evolutionary modelling: from trees to bumble bees

报告摘要：Our understanding of evolution has advanced significantly since the theory of natural selection was first formulated by Wallace and Darwin in 1858. Although we cannot predict major events such as adaptive radiation and mass extinction, we can predict for example the evolutionary response to environmental change, and the conditions for evolutionary branching. New mathematical tools were developed in the 1990s, introducing simple graphical representations to understand the complex process of evolution. Adaptive dynamics is based on the idea of separation between ecological and evolutionary timescales, and the separation of common residents and rare mutants. In this talk I will go through the basic theory, and give examples from my own research.

报告人：Peter Fransson瑞典于默奥大学

报告题目：Model-based investigation on the effects of spatial evenness, and size selection in thinning of Norwegian spruce stands

报告摘要：Size- and spatial distribution of trees are important for forest stand growth, but it has rarely been documented to what degree they matter in thinning operations, in terms of wood production and stand economy. Here we investigate how the choice of spatial evenness and tree-size distribution of residual trees will impact wood production and stand economy. A spatially explicit individual-based growth model was used, in conjunction with empirical cost functions for harvesting and forwarding, to calculate net production and net present value for different thinning operations in Norway spruce stands in Northern Sweden. The in silico thinning operations are defined by three variables: 1) spatial evenness after thinning, 2) tree size preference for harvesting, and 3) basal area reduction.

报告人：Prince Harvim江苏大学

报告题目：Transmission dynamics and control mechanisms of vector-borne diseases with active and passive mobilities between rural towns and urban cities

报告摘要：A metapopulational model, which includes vector-borne and sexual transmission of an epidemic disease with passive and active movements between an urban city and a rural town, is formulated and analysed. The basic reproduction number includes both sexual transmission and vector transmission thresholds. The sensitivity analyses reveal that the disease propagation is mainly through the vector-borne compare to the sexual activity transmission. The optimal control simulation results show that mobility leads to the spread of the disease in the receiving city while there is a reduction of infection in the home city. The population size of the city has a significant role in the spread of the disease. It shows from the simulation results that the rural town with the smaller population size has most of its infected population reduce during the control case compare to the control case in the urban city with larger population size. The disease is not eliminated under the case of control, but it only stabilises for a significant amount of time, which implies that the restriction of movement will reduce the spread of the disease for some time but can not lead to the elimination of the disease.

报告人：张弘 江苏大学

报告题目：Mathematical analysis and optimal strategies for the control of Aedes aegypti mosquito

报告摘要：In this talk, first of all, we introduce a delayed model for the dynamics of a mosquito population which is subject to an integrated strategy that includes pesticide release, the use of mechanical controls and the use of the sterile insect technique (SIT). The existence of positive equilibria is characterized in terms of two threshold quantities, being observed that the ‘richer’equilibrium (with more mosquitoes in the aquatic phase) has better chances to be stable, while a longer duration of the aquatic phase has the potential to destabilize both equilibria. It is also found that the stability of the trivial equilibrium appears to be mostly determined by the value of the maturation rate from the aquatic phase to the adult phase. Secondly, A nonstandard finite difference (NSFD) scheme is devised to preserve the positivity of the approximating solutions and to keep consistency with the continuous model. The resulting discrete model is transformed into a delay-free model by using the method of augmented states, a necessary condition for the existence of optimal controls then determined. The particularities of different control regimes under varying environmental temperature are investigated by means of numerical simulations. Finally, it is observed that a combination of all three controls has the highest impact upon the size of the aquatic population. While at higher environmental temperatures, the oviposition rate has the most prominent influence upon the outcome of the control measures.

报告人：葛静 淮阴师范学院

报告题目：The spatial-temporal risk index and spreading dynamics for a time-periodic diffusive WNv model

报告摘要：In this talk, we will consider a simplified epidemic model for West Nile virus in a heterogeneous time-periodic environment. Using the model, we will investigate the impact of spatial heterogeneity of environment and temporal periodicity on the persistence and eradication of West Nile virus. The free boundary is employed to represent the moving front of the infected region. The basic reproduction number $R_0^D$ and the spatial-temporal risk index $R_0^F(t)$, which depend on spatial heterogeneity, temporal periodicity and spatial diffusion, are defined by considering the associated linearized eigenvalue problem. Sufficient conditions for the spreading and vanishing of West Nile virus are presented for the spatial dynamics of the virus.

报告人：张来 扬州大学

报告题目：Biodiversity loss through speciation collapse: mechanisms, warning signals, and possible rescue

报告摘要：Speciation is the process that generates species diversity. While this process normally adds species to the global species pool, recent empirical findings show that it can also be interrupted, leading to the collapse of speciation. Here, we elucidate the mechanisms behind speciation collapse using a stochastic individual-based model with explicit genetics. We investigate the impact of two types of environmental disturbance: deteriorated visual conditions, which reduce foraging ability as well as impede mate choice, and environmental homogenization, which restructures ecological niches. We find: (1) Species pairs can collapse into a variety of forms including a hybrid swarm, monomorphic or polymorphic generalists, or single specialists. Notably, a hybrid swarm may be a transient stage to a monomorphic population; (2) Restoring the environment makes it possible for species pairs to re-emerge from single generalist forms, but not from single specialist forms; (3) Speciation collapse is up to 4 orders of magnitude faster than speciation, while the re-emergence of species pairs can be as slow as de novo speciation; (4) Demographic, phenotypic, and genetic signals are compared in terms of their usefulness for predicting speciation collapse, yielding that phenotypic signals can be taken as general and robust warning signals for speciation collapse.