Genetic stability of Aedes aegypti populations following invasion by wMel Wolbachia

Abstract

Background: Wolbachia wMel play a major role in mosquito rear and release strategies that aim to inhibit the transmission of arboviruses such as dengue, Zika, Chikungunya and yellow fever. However, the long-term establishment of wMel in natural populations of the dengue mosquito Aedes aegypti raises concerns that interactions between Wolbachia wMel and Ae. aegypti may lead to changes in the host genome, which could affect useful attributes of Wolbachia that allow it to invade and suppress disease transmission. Results: We applied an evolve-and-resequence approach to study genome-wide genetic changes in Ae. aegypti from the Cairns region, Australia, where Wolbachia wMel was first introduced more than 10 years ago. Mosquito samples were collected at three different time points in Gordonvale, Australia, covering the phase before (2010) and after (2013 and 2018) Wolbachia releases; an additional three locations where Wolbachia replacement happened at different times across the last decade were also sampled in 2018. We found that in general, the genome of mosquito populations mostly remained stable after Wolbachia release, with any population differences tending to reflect the geographic location of the populations rather than Wolbachia infection status. Whereas on the other hand, outlier analysis suggested that Wolbachia may have had an influence on some genes related to immune response, development, recognition and behaviour. Conclusions: In general, Ae. aegypti populations remained geographically distinct after Wolbachia releases in North Australia despite their Wolbachia infection status. Whereas at some specific genomic loci, we found signs of selection associated with Wolbachia, suggesting potential evolutionary impacts can happen in the future and further monitoring is warranted.

A decade of stability for wMel Wolbachia in natural Aedes aegypti populations

“…Comparisons of mosquito genomes prior to wMel release in Gordonvale and seven years post-release point to limited changes [38], but further work with replicated populations is required to confirm any changes due to Wolbachia infection.…”

“…We extend this timeframe by including pre-release material from 2010 and field collections from Gordonvale and Yorkeys Knob in 2020. We also include a dataset from a previous whole genome sequencing study of individuals collected from Gordonvale in 2013 and 2018 and Yorkey's Knob in 2018 [38]. Little evidence of change was observed among the analysed wMel genomes, for which we achieved ≥ 99.99% coverage.…”

“…Whole Ae. aegypti [38] and Wolbachia [39,40] genome sequencing studies show limited genomic changes after wMel has been established in Cairns for at least 7 years.…”

Wolbachiainhibits ovarian formation and increases blood feeding rate in femaleAedes aegypti

“…As a result, Wolbachia field release and establishment in new populations can be useful for studying evolutionary changes in Wolbachia given that the invasion history of the population is known [17][18][19].…”