Although management programs for invasive species are generally intended at a regional or national level, physical intervention generally takes place in smaller management units. The ability to predict how local habitat variation will affect the dispersal of invasive species is an essential tool for the efficient targeting of resources to manage the spread of an invasive species. Here we describe a coupled map lattice model for the local spread of a recently discovered devastating pest of Fraxinus spp. in North America, the Emerald Ash Borer, Agrilus planipennis. The model is based on field estimates of population growth, dispersal, larval consumption rates, and developmental thresholds and is designed to be able to incorporate site specific spatially explicit resource variation. We present the functionality of this model by using it to investigate the influence of resource distribution on the spread of A. planipennis, and the relative importance of oviposition site foraging behavior assumptions on the local spread of A. planipennis.
Results/Conclusions
Simulations performed in environments varying in the spatial distribution of resources indicated that the local spread was strongly dependent on both resource distribution and quantity. In particular, a decrease in resource quantity lead to a small increase in the spread rate, while greater resource heterogeneity can lead to either an increase or a decrease in the spread rate. Simulations also indicated that resource consumption rate and a density dependent variation in developmental rate (1 or 2 year larval stages) exhibited by A. planipennis are likely to be key components of this species spread rate. Differences in resource distribution, in environments containing identical quantities of resources, also had a strong impact on the local population size. In addition, the simulations indicated that foraging behavior assumptions, built on top of dispersal estimates from homogeneous sites, can lead to large differences in both the spread rate and population sizes. Together these results illustrate 1) the need to incorporate habitat heterogeneity when considering potential management options, and 2) the importance of considering behavior in the population dynamics of invasive insect species.
