Molecules and models for tracking invasion processes: Tetranychus evansi as an emerging pest

By combining genetic variation information based on molecular markers (microsatellite loci) and recent developments in Approximate Bayesian Computation (ABC), we investigated the invasion process of the red tomato spider mite Tetranychus evansi which has emerged in the last 10 years as a new destructive pest of solanaceous crops worldwide. By distinguishing among alternative colonization pathways and estimating the timing of introductions, our study identified the routes of the expansion of the mite. Data unravelled that multiple introductions occurred from the origin area of the mite in South America to Africa and Europe, and that subsequent recent admixture of two invading lineages occurred. Because when shifting their geographic range, species may respond to new environments by adapting locally to new conditions, we also modeled current distributions of T. evansi and under different scenarios of climate change. While molecules helped to trace the historical reconstruction of the invasion and explain the present distribution, models provided information to predict future potential range expansion of the mite. Combining information from molecules and models helps not only to understand invasion biology but also to refine management strategies and to prevent further spread of an emerging pest.