Inferences on population history of a seed chalcid wasp: invasion success despite a severe founder effect from an unexpected source population

Abstract

Most invasive species established in E urope originate from either A sia or N orth A merica, but little is currently known about the potential of the A natolian P eninsula ( A sia M inor) and/or the N ear E ast to constitute invasion sources. Mediterranean forests are generally fragile ecosystems that can be threatened by invasive organisms coming from different regions of the M editerranean B asin, but for which historical data are difficult to gather and the phylogeographic patterns are still poorly understood for most terrestrial organisms. In this study, we characterized the genetic structure of M egastigmus schimitscheki , an invasive seed‐feeding insect species originating from the Near East, and elucidated its invasion route in S outh‐eastern F rance in the mid 1990s. To disentangle the evolutionary history of this introduction, we gathered samples from the main native regions ( T aurus M ountains in T urkey, L ebanon and C yprus) and from the invaded region that we genotyped using five microsatellite markers and for which we sequenced the mitochondrial C ytochrome O xidase I gene. We applied a set of population genetic statistics and methods, including approximate Bayesian computation. We proposed a detailed phylogeographic pattern for the N ear E ast populations, and we unambiguously showed that the French invasive populations originated from C yprus, although the available historical data strongly suggested that T urkey could be the most plausible source area. Interestingly, we could show that the introduced populations were founded from an extremely restricted number of individuals that realized a host switch from C edrus brevifolia to C . atlantica . Evolutionary hypotheses are discussed to account for this unlikely scenario.

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