The hitchhiker's guide to becoming invasive: exotic mosquitoes spread across a US state by human transport not autonomous flight

Abstract

Not all exotic species establish and expand aggressively (i.e. become invasive). As potential vectors of disease agents, invasive mosquitoes can have considerable impact on public health, livestock and wildlife; therefore, understanding the species characteristics and ecological circumstances promoting their invasiveness is important. The mosquito Aedes japonicus japonicus, originally from north-east Asia, was introduced at least two separate times to the north-eastern USA, as surmised from the initial existence of two populations with distinct nuclear and mitochondrial genetic signatures that later intermixed. Since these original introductions in the late 1990s, Ae. j. japonicus has expanded across 31 US states, two Canadian provinces and five European countries. Although some of the expanded range was due to other independent introductions, to understand what drove the postintroduction expansion of Ae. j. japonicus within the north-eastern USA, we performed a high-resolution landscape genetic analysis of 461 specimens collected across Virginia, a state south of the original introductions. All specimens were genotyped at seven pre-optimized microsatellite loci, and a subsample was sequenced at one mitochondrial locus. We concluded that throughout Virginia this species has primarily expanded in association with humans: genetic distance and distance along roads remained correlated after controlling for geographic distance, and proximity to I-95, a major interstate highway, strongly predicted nuclear ancestry. In contrast, there was very limited evidence of diffusion even at distances potentially suitable for autonomous mosquito flight. This implies that its association with humans (rather than innate species characteristics) is the single most important determinant of invasiveness in this mosquito.

The genetic diversity and population structure of domestic Aedes aegypti (Diptera: Culicidae) in Yunnan Province, southwestern China

“…Most species can be transported to a new geographical area via human activities but either fail to establish or maintain their population with minimal impact [51]. By definition, the progress of one exotic species to the level of a biological invasion involves a significant increase within its new territory [52].…”

Population genomics of the Asian tiger mosquito, Aedes albopictus: insights into the recent worldwide invasion

“…albopictus, two life-history traits are particularly important to ecological adaptations during the range expansion of this species. First, its affinity to human-made containers and environments allowed this species to quickly expand its range within and among continents due to regional and global trade among distant geographic regions (Medley, Jenkins, & Hoffman, 2015;Tatem, Hay, & Rogers, 2006) as has been observed in other Aedes species as well (Damal, Murrell, Juliano, Conn, & Loew, 2013;Egizi, Kiser, Abadam, & Fonseca, 2016). Second, the capacity for facultative photoperiodic diapause (Hawley, 1988;Mori, Oda, & Wada, 1981;Urbanski, Benoit, Michaud, Denlinger, & Armbruster, 2010) is largely responsible for the capacity of this mosquito to adapt to a temperate climate, enabling its range expansion into regions at higher latitudes in North America and North Europe (Armbruster, 2016;Becker et al, 2013;Flacio, Engeler, Tonolla, & Müller, 2016;Urbanski et al, 2010).…”

Fine-Scale Population Genetic Structure of Dengue Mosquito Vector, Aedes aegypti and its Association to Local Dengue Incidence

“…aegypti by human-mediated transportation. It is believed that mosquito vectors occasionally travel in long distances by taking advantage human-aided transportation routes via land, sea or air [52,53,54] as Ae. aegypti eggs, larvae and adults have been found in commercial trucks and ships through tire importation [55,56].…”