Aedes albopictus is one of the world's most invasive species and a vector of arboviruses that cause important human diseases.
Despite many published studies on the introduction and establishment of Ae. albopictus into new areas of the globe, the process of initial spread following introduction is poorly understood as observing this process is fraught with challenges. Models offer a way to address some of these challenges. Simulation of the dynamics of introduced populations sheds light on the chain of events that eventually results in the invasion of a species in new areas.
The goal of this study was to develop a model which accounts for the reproduction, development, survival and movement of Ae. albopictus in complex urban landscapes. We blended a fitted statistical model for landscape suitability with a dynamical model for population processes. The resulting model was used to understand the effect of year-to-year and seasonal variability on introductions due to climate fluctuations, and the effect of the mosquito life stage introduced on the invasion process. The study area included two cities located in eastern Los Angeles, California that have been foci of Ae. abopictus surveillance and detection since its discovery there in 2011.
Results/Conclusions
We found that the probability to observe a successful introduction in the study area was low, and eggs and immatures introduced in spring were the only successful introduction scenarios. The age structure of the population was often dominated by eggs, with adults never representing more than 5%. However, this pattern was disrupted by adverse climatic conditions, and just before extinction. The spread of introduced populations was also low, with populations never dispersing more than 600 m from the location of introduction, in agreement with Ae. albopictus ecology, and sedentary behavior in urban areas.
Overall, results indicated that the introduction of eggs or larvae during spring months were the most likely events underpinning Ae. albopictus invasion in the study area. However, our results also suggested that any successfully introduced population would have remained localized in space and at low density for some time thus were difficult to discover. This finding may also support the hypothesis that the introduction of Ae. albopictus in the study area occurred years before its discovery, as this species could have remained in low undetectable densities. The developed integrative model is a flexible tool to investigate the Ae. albopictus invasion, that can bring important advances in knowledge to improve control actions.