Evolution of plant defenses during a plant invasion

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Biological invasions are an increasing global problem, with dramatic ecological and economic consequences. To manage current invaders and prevent future invasions it is critical to understand the processes underlying successful biological invasions. For instance, we know that successful invasive species often rapidly evolve and adapt to their novel environments, in particular to altered enemy pressures. The precise mechanisms, from genome to plant phenotypes and biotic interactions, are however rarely understood. Moreover, a true understanding of an invasive species requires a cross-continental perspective, and the comparison of its ecology and evolution in the native versus introduced range. Here, we propose an integrative and cross-continental study of the aggressive plant invader Japanese knotweed (Reynoutria japonica), which experiences drastic changes in herbivore pressure in its introduced range. To understand the evolutionary processes during this invasion, and its underlying mechanisms, we have assembled a German-Chinese team of leading invasion biologists with complementary expertises. Our project takes advantage of an ongoing global survey and molecular analysis of 200 invasive knotweed populations from across the native (China/Japan) and invasive (USA/Europe) range. We will build on the resources of this project and examine herbivory and plant herbivore resistance on a global scale, and how these are associated with underlying variation in plant secondary chemistry, as well as with (epi-)genomic and transcriptome variation. To achieve this, we will combine field observation with common-garden and experimental approaches, and with metabolomic and genomic methods. Our project will be unique in its combination of geographic scale and biological depth, and it will provide important insights about one of the world’s worst invasive species. We hope that it will become a model for successful cross-continental collaboration.