Abstracts (first author)
Post-introduction evolutionary rescue
Invasive mosquitoes have caused inordinate human suffering because they are very abundant in their exotic ranges and can drive local or exotic disease evolution and epidemics. Invasive mosquitoes often exploit domestic environments, and the resulting extensive overlap with humans significantly enhances their effectiveness as vectors of human diseases. It is unclear, however, whether domestication was a pre-condition for invasiveness or instead a consequence of it. To understand factors that deter or promote invasiveness we studied Aedes japonicus japonicus, a mosquito native to East Asia that has become invasive in some parts of its new range in North America and Europe. We traced the source of all exotic populations to central Japan, where we found high genetic diversity but homogeneity across populations indicating ongoing gene flow. Spatiotemporal analyses of exotic populations revealed that (1) populations across the exotic range had very different genetic signatures; (2) genetic diversity declined precipitously outward from introduction points; (3) the spatial extent of local infestations correlated strongly with genetic diversity but at different scales in the US and in Europe; (4) all broadly expanding populations (=invasive) had genetic signatures resulting from admixture of separate introductions. We propose that human-assisted rapid movement of specimens across the exotic range “rescued” self-limiting introductions by mixing locally differentiated genotypes. We propose that invasiveness is not a required pre-existing trait in invasive mosquitoes, but instead can evolve in the exotic range leading inexorably to dangerous human disease vectors.