Migration and dispersal may drive to high genetic variation and significant genetic mixing: the case of two agriculturally important, continental hoverflies ( E pisyrphus balteatus and S phaerophoria scripta )

Abstract Population structure of pests and beneficial species is an important issue when designing management strategies to optimize ecosystem services. In this study, we investigated for the first time the population structure at a continental scale of two migratory species of hoverflies providing both pest regulation and pollination services [ E pisyrphus balteatus and S phaerophoria scripta (Diptera: Syrphidae)]. To achieve this objective, we used two sets of 12 species‐specific microsatellite markers on a large‐scale sampling from all over E urope. Our findings showed a high level of genetic mixing resulting in a lack of genetic differentiation at a continental scale and a great genetic diversity in the two species. All the pairwise F ST values between European localities were less 0.05 in the two species. These low values reflect a large‐scale genetic mixing probably caused by the existence of frequent migratory movements in the two species. M antel tests revealed isolation‐by‐distance pattern on the E ast– W est axis, but not on the N orth– S outh axis. This isolation‐by‐distance pattern confirms the existence of N orth– S outh migratory movements in both directions and suggests an important step by step dispersal. Population features shown by this study are common in invasive species and pests, but are not often observed in beneficial species. They reflect great colonization abilities and a high adaptive potential when dealing with a changing environment. Our results highlight the two studied species as particularly interesting beneficial insects for pollination and pest predation in the current context of global change.