Some insects like mosquitoes are characterized by a complex life cycle, where different developmental stages not only vary in their demographic rates, but rather inhabit distinct habitats. Accurately predicting the dynamics of such populations requires developing stage-structured population models, also incorporating habitat spatial structure and heterogeneity. We developed a spatial and stage-structured model aiming to test for the consequences of spatial heterogeneity in larval development rate combined with varying management regimes and dispersal kernels on the population persistence on two mosquito species: Aedes albopictus (short-dispersing species) and Culex quinquefasciatus (long-dispersing species). We simulated two different environments, homogenous and heterogeneous, while keeping the average per patch asymptotic growth rate equal. Specifically, in the homogeneous environment, the quality of all aquatic habitats was the same, leading to consistent larval developmental times and to spatial synchrony in adult emergence. In the heterogeneous environment, half of the aquatic habitats were characterized by shorter larval developmental time and lower adult survival and fecundity, while the inverse pattern occurred in the other half. Doing so generated spatial asynchrony in adult emergence. Considering the management regime, we systematically increased the temporal variation in per patch extinction probability, while keeping the mean extinction rate constant.
Results/Conclusions
Population size and explosion probability were lower in the homogeneous than in the heterogeneous environment. As expected, these differences were moderated as the tail of the dispersal kernel became thicker. We suggest that spatial heterogeneity triggered asynchrony in adult emergence, thus increasing regional persistence via the rescuing of aquatic habitats that undergone local extinction. Moreover, population persistence of both species decreased with increased temporal variation in per patch extinction probability. Again, this effect weakened as the tail of the dispersal kernel became thicker, especially in the long-dispersing species. We thus suggest that efficiently controlling these mosquitoes requires dividing the same total management effort over few events, simultaneously exterminating as many as possible sub-populations, rather than frequently exterminating only a few of them. For instance, spraying pesticide (e.g., Bacillus thuringiensis israelensis), exterminating the larvae in the aquatic habitats, is more efficient when all aquatic habitats are sprayed every X days, rather than randomly spraying only half of them every X/2 days or quarter of them every X/4 days. This study represents a rare attempt to integrate processes affecting the persistence of stage-structured mosquito populations at multiple spatial scales, serving as a precondition for developing efficient mosquito control programs.