Multiple introductions of the dengue vector, Aedes aegypti, into California

Abstract

The yellow fever mosquito Aedes aegypti inhabits much of the tropical and subtropical world and is a primary vector of dengue, Zika, and chikungunya viruses. Breeding populations of A. aegypti were first reported in California (CA) in 2013. Initial genetic analyses using 12 microsatellites on collections from Northern CA in 2013 indicated the South Central US region as the likely source of the introduction. We expanded genetic analyses of CA A. aegypti by: (a) examining additional Northern CA samples and including samples from Southern CA, (b) including more southern US populations for comparison, and (c) genotyping a subset of samples at 15,698 SNPs. Major results are: (1) Northern and Southern CA populations are distinct. (2) Northern populations are more genetically diverse than Southern CA populations. (3) Northern and Southern CA groups were likely founded by two independent introductions which came from the South Central US and Southwest US/northern Mexico regions respectively. (4) Our genetic data suggest that the founding events giving rise to the Northern CA and Southern CA populations likely occurred before the populations were first recognized in 2013 and 2014, respectively. (5) A Northern CA population analyzed at multiple time-points (two years apart) is genetically stable, consistent with permanent in situ breeding. These results expand previous work on the origin of California A. aegypti with the novel finding that this species entered California on multiple occasions, likely some years before its initial detection. This work has implications for mosquito surveillance and vector control activities not only in California but also in other regions where the distribution of this invasive mosquito is expanding.

Wolbachia pipientis occurs in Aedes aegypti populations in New Mexico and Florida, USA

“…aegypti into which the bacterium has been artificially transinfected(Ant, Herd, Geoghegan, Hoffmann, & Sinkins, 2018). aegypti populations from Las Cruces, New Mexico, Houston, Texas, and four locations of Florida are genetically distinct(Pless et al, 2017). aegypti samples in our study.…”

“…It has been shown that Ae. aegypti populations from Las Cruces, New Mexico, Houston, Texas, and four locations of Florida are genetically distinct(Pless et al, 2017). Further studies are needed to tease out the roles of these potential drivers of Wolbachia presence and abundance in Ae.…”

Effective population sizes of a major vector of human diseases, Aedes aegypti

“…We estimated N e with two different temporal methods that are robust to the potential bias introduced by overlapping generations (Luikart et al., ; Waples, ). We combined datasets previously generated in our laboratory at Yale University (Brown et al., ; Gloria‐Soria et al., ; Gloria‐Soria, Ayala, et al., ; Gloria‐Soria, Kellner, et al., ; Monteiro et al., ; Pless et al., in review) with newly genotyped mosquitos. The final microsatellite dataset included 12 loci from an average of 46.7 individuals per time point sampled (Table ).…”

Population structure of a vector of human diseases: Aedes aegypti in its ancestral range, Africa

“…While populations outside Africa (largely conforming to Aaa) have been well-studied and strong genetic structure among and within continents have been documented [e.g., (Bosio et al, 2005;Bracco, Capurro, Lourenço-de-Oliveira, & Sallum, 2007;Brown et al, 2011Brown et al, , 2014Gloria-Soria et al, 2016;Gonçalves da Silva et al, 2012;Kotsakiozi, Gloria-Soria, Schaffner, Robert, & Powell, 2018;Kotsakiozi, Gloria-Soria et al, 2017;Mousson, Dauga, Garrigues, & Schaffner, 2005;Pless et al, 2017;Rašić et al, 2015;Scarpassa, Cardoza, & Cardoso, 2008)], the ancestral populations in Africa have been understudied. Even Ae.…”