Incursion pathways of the Asian tiger mosquito (Aedes albopictus) into Australia contrast sharply with those of the yellow fever mosquito (Aedes aegypti)

Abstract

BACKGROUNDUnderstanding pest incursion pathways is critical for preventing new invasions and for stopping the transfer of alleles that reduce the efficacy of local control methods. The mosquitoes Aedes albopictus (Skuse) and Ae. aegypti (Linnaeus) are both highly invasive disease vectors, and through a series of ongoing international incursions are continuing to colonise new regions and spread insecticide resistance alleles among established populations. This study uses high-resolution molecular markers and a set of 241 reference genotypes to trace incursion pathways of Ae. albopictus into mainland Australia, where no successful invasions have yet been observed. We contrast these results with incursion pathways of Ae. aegypti, investigated previously.RESULTSAssignments successful identified China, Japan, Singapore and Taiwan as source locations. Incursion pathways of Ae. albopictus were entirely different to those of Ae. aegypti, despite broad sympatry of these species throughout the Indo-Pacific region. Incursions of Ae. albopictus appeared to have come predominantly along marine routes from key trading locations, while Ae. aegypti was mostly linked to aerial routes from tourism hotspots.CONCLUSIONThese results demonstrate how genomics can help decipher otherwise cryptic incursion pathways. The inclusion of reference genotypes from the Americas may help resolve some unsuccessful assignments. While many congeneric taxa will share common incursion pathways, this study highlights that this is not always the case, and incursion pathways of important taxa should be specifically investigated. Species differences in aerial and marine incursion rates may reflect the efficacy of ongoing control programs such as aircraft disinsection.

Population genomics of two invasive mosquitoes (Aedes aegypti and Aedes albopictus) from the Indo-Pacific

“…albopictus occurred at a time when international shipping routes more closely resembled the 2004 routes analysed here. Although dispersal by aircraft may be less common than by shipping in this species [ 25 ], it is worth noting that much of the material used in this study was collected near to international airports, which may exaggerate the influence of the aerial dispersal network. Also, as the metric for aerial connectivity was derived from the activity of nearby airports, aerial connectivity scores may correlate closely with other untested variables that could influence regional genetic structure, such as economic activity.…”

“…albopictus found more frequently at seaports and Ae . aegypti at airports [ 25 ]. The most common source of Ae .…”

“…described here has implications for biosecurity and biocontrol. Recently, genomics has been used to identify source locations of Aedes incursions into Australia and New Zealand [ 20 , 25 ]; these incursions threaten not only the arrival of species themselves but also the introduction of insecticide resistance alleles [ 24 ]. The genomic patterns identified here can help in identifying biosecurity threats in both species, both by revealing likely pathways of gene flow and demonstrating that long-distance marine incursions may be more likely in Ae .…”

“…populations can spread advantageous alleles that reduce the efficacy of local control programs [ 24 ]. Incursions of these species are frequently linked to vessels such as ships and planes [ 19 , 20 , 25 ], and when source locations can be identified they are often far from the point of collection [ 20 , 25 ].…”

Molecular relationships of introducedAedes japonicus(Diptera: Culicidae) populations in British Columbia, Canada using mitochondrial DNA

“…Genetic diversity characterization allows us to monitor new arrivals of invasive species by identifying genetic variations between and within populations. Determining genetic relationships depends on the presence of high‐quality genetic material, reliable and comprehensive reference datasets with comparable genetic sequences, as well as wide geographical survey range (Casiraghi et al 2010, Schmidt et al 2020). Over the last decade, mitochondrial DNA (mtDNA) sequences have been used extensively in population genetic studies.…”