Population genomics of two invasive mosquitoes (Aedes aegyptiandAedes albopictus) from the Indo-Pacific
Authors: Schmidt Thomas L , Chung Jessica , Honnen Ann-Christin , Weeks Andrew R , Hoffmann Ary A 
Published: March 2020

The arbovirus vectorsAedes aegypti(yellow fever mosquito) andAe. albopictus(Asian tiger mosquito) are both common throughout the Indo-Pacific region, where 70% of global dengue transmission occurs. ForAe. aegyptiall Indo-Pacific populations are invasive, having spread from an initial native range of Africa, while forAe. albopictusthe Indo-Pacific includes invasive populations and those from the native range: putatively, India to Japan to Southeast Asia. This study analyses the population genomics of 480 of these mosquitoes sampled from 27 locations in the Indo-Pacific. We investigated patterns of genome-wide genetic differentiation to compare pathways of invasion and ongoing gene flow in both species, and to compare invasive and native-range populations ofAe. albopictus. We also tested landscape genomic hypotheses that genetic differentiation would increase with geographical distance and be lower between locations with high connectivity to human transportation routes, the primary means of dispersal at these scales. We found that genetic distances were generally higher inAe. aegypti, with Pacific populations the most highly differentiated. The most differentiatedAe. albopictuspopulations were in Vanuatu, Indonesia and Sri Lanka, the latter two representing potential native-range populations and potential cryptic subspeciation respectively. Genetic distances inAe. aegyptiincreased with geographical distance, while inAe. albopictusthey decreased with higher connectivity to human transportation routes. Contrary to the situation inAe. aegypti, we found evidence of long-distanceAe. albopictuscolonisation events, including colonisation of Mauritius from East Asia and of Fiji from Southeast Asia. These direct genomic comparisons indicate likely differences in dispersal ecology in these species, despite their broadly sympatric distributions and similar use of human transport to disperse. Our findings will assist biosecurity operations to trace the source of invasive material and for biocontrol operations that benefit from matching genetic backgrounds of released and local populations.

Author Summary

The mosquitoesAe. aegyptiandAe. albopictusare highly invasive and transmit dengue and other arboviruses. This study investigates the genetics of these mosquitoes in the Indo-Pacific region, where 70% of global dengue transmission occurs and where both species have established widespread invasions by hitch-hiking on human transport vessels. We compared patterns of genetic differentiation to determine the pathways these species have taken while spreading through the Indo-Pacific, and to better understand how they disperse. We sequenced DNA from 480 mosquitoes sampled from 27 locations in the Indo-Pacific, and found many genetic differences between the two species. Populations ofAe. aegypti, which is not native to the region, tended to be genetically different from each other, and populations in the Pacific Ocean were particularly divergent.Aedes albopictuspopulations were generally more similar to each other, though genetically different populations in Sri Lanka and Indonesia point to these having a different history to other populations. Genetic differences betweenAe. aegyptipopulations were larger when populations were geographically distant, while differences betweenAe. albopictuspopulations were larger when populations likely had limited access to human transportation. These results will help improve strategies for controlling these species and stopping their spread around the world.