Importance of endogenous feedback controlling the long-term abundance of tropical mosquito species

Mosquitoes are a major vector for tropical diseases, so understanding aspects that modify their population dynamics is vital for their control and protecting human health. Maximising the efficiency of control strategies for reducing transmission risk requires as a first step the understanding of the intrinsic population dynamics of vectors. We fitted a set of density-dependent and density-independent models to the long-term time series of six tropical mosquito species from northern Australia. The models’ strength of evidence was assessed using Akaike’s Information Criterion (AIC_c), Bayesian Information Criterion (BIC) and jack-knifed cross-validation (C-V). Density dependence accounted for more than 99% of the model weight in all model-selection methods, with the Gompertz-logistic (Cushing model) being the best-supported model for all mosquito species (negative density feedback expressed even at low densities). The second-most abundant species, Aedes vigilax (a saline breeder), showed no spatial heterogeneity in its density-dependent response, but the remaining five species had different intrinsic growth rates across 11 study sites. Population densities of saline species were high only during the late dry to early wet season following the highest tides of the month or early flood rains when swamps were mostly saline, whereas those of freshwater species were highest during the mid-wet and mid-dry seasons. These findings demonstrate remarkably strong density dependence in mosquito populations, but also suggest that environmental drivers, such as rainfall and tides, are important in modifying seasonal densities. Neglecting to account for strong density feedback in tropical mosquito populations will clearly result in less effective control.