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Traits leading to invasion: how did the tomato spider mite Tetranychus evansi colonize Europe?
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National audience. What allows a species or population to invade once a propagule arrives to a new geographical area, remains poorly understood. There ismuch research focused on differences in the traits possessed by invasive species relative to non-invasive introduced species. However, thedifferent evolutionary histories of the species, and often differences in the environments they invade, make difficult to know which traitsplay a large role in invasion. We are studying the invasion history and biology of the tomato spider mite, Tetranychus evansi, a mite thatoriginates from South America and has recently emerged as a new threat to solanaceous crops in Africa and in the Mediterranean basin.Our research has revealed that two main lineages are present in Europe. Differences in their geographical distribution and populationdynamics suggest that they differ dramatically in invasive potential. This provides an excellent opportunity to evaluate what biological traitsdiffer between more invasive and less invasive lineage. We investigate two biological traits that appear likely to be key for the success ofthe invasion of T. evansi in newly colonized temperate climates: cold tolerance and host range. The species is not able to diapause, thus itsinvasion of a temperate environment is likely to rely upon its ability to tolerate cold. Additionally, though considered to be a specialist, as withmany herbivorous insects, and its ability to exploit different species of plants is not equal, and the range of plants in the new environmentlikely differs from the native area. We experimentally compare life-history parameters of mites from the more and less invasive lineages andsubmitted them to different temperatures and host plants. We find that the more invasive lineages is more cold tolerant and has a broaderhost range. This supports the idea that ‘general purpose genotypes’ are particularly suited to invasion.
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