Urban population structure and dispersal of an Australian mosquito (Aedes notoscriptus) involved in disease transmission

Abstract

Successful species management is reliant upon understanding key ecological features of the target species and the environment. Dispersal is a critical factor to assess when designing control measures as it determines the rate of migration out of or into controlled areas and influences the risk of human exposure to the species and its pathogens. This study uses spatial population genomics to investigate the movement ecology of Aedes notoscriptus, an important disease transmitting mosquito, at the Mornington Peninsula, Australia. We sampled Ae. notoscriptus eggs from the Mornington Peninsula at a single time point, and generated genomic data from 240 individuals from different locations. We also produced a draft genome assembly for this clade of Ae. notoscriptus. We used genomic data to detect close kin dyads, and the locations of dyads showed that specific acts of movement in the previous generation had occurred over distances >1 km. We also investigated isolation by distance patterns from the spatial autocorrelation of genetic distances. Significant genetic dissimilarity in Ae. notoscriptus began to be observed at >4 km separation, a fourfold higher distance than in a comparable sample of the dengue mosquito Ae. aegypti. These findings are evidence that the high mobility of Ae. notoscriptus influenced the success of a 2021 mosquito control trial at the Mornington Peninsula, because the dispersal ability of Ae. notoscriptus was likely to have exceeded the size of the intervention zones which were designed around ecological knowledge of Ae. aegypti. Further sampling within the same area was used to obtain counts of Ae. notoscriptus eggs at two timepoints 6 and 12 months after initial sampling. We found egg counts to be consistent across timepoints, and spatial variation in egg counts was found to covary with spatial variation in neighbourhood size (NS). As NS increases linearly with population density, this is evidence that egg counts may be useful for estimating relative density in Ae. notoscriptus. The overall results of this study draw attention to the importance of acquiring species-specific data when planning control measures, and contribute to the fundamental ecological understanding of this important vector species.