Quantifying Aedes aegypti dispersal in space and time: a modeling approach

The dispersal of the invasive mosquito Aedes aegypti in urbanized areas has received attention due to the hazard that this species poses to human health. However, we know little about this process at temperate latitudes, especially in recently colonized semi-arid regions of the southwestern United States that differ ecologically from more typical habitats in the tropics. We collected data on Ae. aegypti dispersal through a mark-release-recapture (MRR) study in Central California. We employed stable isotopes of carbon and nitrogen to mark released mosquitoes. We characterized Ae. aegypti dispersal capacity using both traditional measures of central tendency and dispersal kernel theory coupled with space-time models, allowing for effects of environmental factors to provide more reliable dispersal estimates. Dispersal of Ae. aegypti was similar between females and males, and we found the mean distances traveled to be 224-240 m from the release location when estimated by conventional methods. Model-based inference allowed for a more nuanced interpretation, with even greater dispersal distances possible depending on direction and environmental context. Our results showed that experimental conditions, such as spatial arrangement of traps and duration of the recapture period, as well as environmental conditions, such as wind speed and direction, altered the probability of recapturing marked mosquitoes, and therefore the observed dispersal pattern. This represents the first assessment of Ae. aegypti dispersal in the semi-arid southwestern United States, which is unique among published studies in that the period of peak annual Ae. aegypti abundance coincides with cumulative precipitation close to zero. Results show that this species dispersed on average farther than commonly documented for other areas of the world. Our findings provide information for defining spatial control strategies, such as incompatible insect technique, which rely on a clear understanding of dispersal rates among neighboring areas.