Steven White (Centre for Ecology and Hydrology), 2 Nov. 2016:

Predicting species spread in heterogeneous landscapes

Characterising the spread of biological populations is crucial in responding to both species and disease invasions, and the shifting of habitat under climate change. Predicting the spreading speeds of such invasions can be studied through mathematical models such as the discrete-time integro-difference equation (IDE) framework. The usual approach in implementing such models has been to ignore spatial variation in the demographic and dispersal parameters and to assume that these are spatially homogeneous. On the other hand, real landscapes are rarely spatially uniform with environmental variation being very important in determining biological spread. In this talk I will demonstrate two new analytical methods for approximating the wavespeed of species invasion for different types of heterogeneous landscapes, which depend on landscape and dispersal scales. Then, I will show a new efficient simulation technique for predicting species spread in 2D heterogeneous landscapes. The technique, an adaptive algorithm, leads to an order of magnitude improvement in computational efficiency (RAM and CPU) over non-adaptive algorithms. I will demonstrate the user-friendly interface which is adaptable to many types of large scale species spread problems. Finally, I will present a case study on the spread of Xylella fastidiosa, a bacterial disease of olive trees which is spreading throughout the Italian region of Apulia. I will demonstrate how the control measures currently being implemented in the region might reduce the impact of the disease.