Abstract
The role of the northward expansion of Culicoides imicola Kieffer in recent and unprecedented outbreaks of Culicoides-borne arboviruses in southern Europe has been a significant point of contention. We combined entomological surveys, movement simulations of air-borne particles, and population genetics to reconstruct the chain of events that led to a newly colonized French area nestled at the northern foot of the Pyrenees. Simulating the movement of air-borne particles evidenced frequent wind-transport events allowing, within at most 36 hours, the immigration of midges from north-eastern Spain and Balearic Islands, and, as rare events, their immigration from Corsica. Completing the puzzle, population genetic analyses discriminated Corsica as the origin of the new population and identified two successive colonization events within west-Mediterranean basin. Our findings are of considerable importance when trying to understand the invasion of new territories by expanding species.
Highlights
Long-distance dispersal, most importantly their ability to diapause at egg stages that allows survival of periods of desiccation, and the exploitation of ephemeral water sources
Rapid expansions in distribution associated with global trade have not generally been reported for the genus Culicoides Latreille (Diptera: Ceratopogonidae)[7,8], this has been hypothesized for C. jamaicensis Edwards[9] and C. belkini (Wirth and Arnaud)[10]
This study reports a second incursion of C. imicola in continental France beyond the apparent northern edge of the species distribution
Summary
Long-distance dispersal, most importantly their ability to diapause at egg stages that allows survival of periods of desiccation, and the exploitation of ephemeral water sources. Within Europe, it has been hypothesized that changes in the northern limits of C. imicola Kieffer in the Mediterranean basin have occurred and coincided with an unprecedented expansion of BTV in this region[13,14,15]. This hypothesis is challenged by recent genetic analyses that supported a long-time presence of C. imicola in the Mediterranean basin[16,17]. In the Iberian Peninsula, the first recorded BTV outbreaks occurred in the 1960’s but confirmed presence of C. imicola populations was first reported in 1983 in Spain[26] and soon afterwards in Portugal[27]. There, the local expansion of the species distribution was estimated as 14.5 km/year and thought to be restricted by physical barriers and the limitation of both suitable larval habitats and suitable hosts for blood-feeding[13]
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