Sex-specific distribution and classification of Wolbachia infections and mitochondrial DNA haplogroups in Aedes albopictus from the Indo-Pacific

Abstract

The arbovirus vectorAedes albopictus(Asian tiger mosquito) is common throughout the Indo-Pacific region, where most global dengue transmission occurs. We analysed population genomic data and tested for cryptic species in 160Ae.albopictussampled from 16 locations across this region. We found no evidence of crypticAe.albopictusbut found multiple intraspecific COI haplotypes partitioned into groups representing three Asian lineages: East Asia, Southeast Asia and Indonesia. Papua New Guinea (PNG), Vanuatu and Christmas Island shared recent coancestry, and Indonesia and Timor-Leste were likely invaded from East Asia. We used a machine learning trained on morphologically sexed samples to classify sexes using multiple genetic features and then characterized thewAlbA andwAlbBWolbachiainfections in 664 other samples. ThewAlbA andwAlbB infections as detected by qPCR showed markedly different patterns in the sexes. For females, most populations had a very high double infection incidence, with 67% being the lowest value (from Timor-Leste). For males, the incidence of double infections ranged from 100% (PNG) to 0% (Vanuatu). Only 6 females were infected solely by thewAlbA infection, while rare uninfected mosquitoes were found in both sexes. ThewAlbA andwAlbB densities varied significantly among populations. For mosquitoes from Torres Strait and Vietnam, thewAlbB density was similar in single-infected and superinfected (wAlbA andwAlbB) mosquitoes. There was a positive association betweenwAlbA andwAlbB infection densities in superinfectedAe.albopictus. Our findings provide no evidence of cryptic species ofAe.albopictusin the region and suggest site-specific factors influencing the incidence ofWolbachiainfections and their densities. We also demonstrate the usefulness of ddRAD tag depths as sex-specific mosquito markers. The results provide baseline data for the exploitation ofWolbachia-induced cytoplasmic incompatibility (CI) in dengue control.