Ragweeds in Europe: What makes a successful plant invader?

Three ragweed species arrived in Europe at roughly the same time, but one has spread aggressively while the others have barely gained a foothold—and researchers want to know why. This matters because invasive species are the second biggest threat to global biodiversity, and ragweed in particular causes severe hay fever and cuts crop yields when it invades farmland. Current prevention efforts are hampered by a lack of understanding of what makes some introductions succeed while others fail. The team will analyse historical herbarium specimens to track the invaders’ genetic changes over time, and examine the microbes living on and inside the plants’ leaves and roots to see whether beneficial or pathogenic microbes influence invasion success. If this hologenomic approach works, it could reveal the genomic and microbial markers that predict whether a newly introduced species will become invasive. That knowledge would help biosecurity officials prioritise which species to monitor and where to intervene, potentially reducing the spread of ragweed and other harmful invaders. The research is fundamental science—it asks how evolution and microbial partnerships shape invasion—but similar work on invasive species has previously informed practical strategies for containment and eradication.