Molecular Barcoding Uncovers Hidden Invasive Plant Threat in South Georgia's Seed Banks

South Georgia, a remote sub-Antarctic island, faces significant ecological challenges from invasive species, compounded by the impacts of climate change. With 41 introduced vascular plant species compared to only 24 native ones, the island's biodiversity is at risk. To combat this, the South Georgia Non-Native Plant Management Strategy was initiated, and this research aimed to understand which non-native species persist in the soil seed bank and contribute to seed dispersal, crucial for effective long-term management.

Using an innovative molecular barcoding approach, the researchers optimized a high-throughput Angiosperms353 sequencing pipeline. They created a comprehensive reference library of all native and non-native species on the island, then applied this to identify species from 1,498 emergent seedlings grown from soil samples and 737 wind-trapped seeds. This method successfully identified 21 distinct species, comprising 10 non-native and 11 native plants.

The findings revealed a striking imbalance. As lead author Viruel notes in the paper, "Strikingly, 84% of emergent seedlings were non-native, with Class III invasive species (Cerastium fontanum, Poa annua, Taraxacum officinale) dominating across most sites and in all wind traps." These dominant Class III invasive species highlight a significant challenge. While management efforts have successfully reduced the spread of Class I and II invasive species, the study confirmed that viable seeds from these plants still persist within the soil, posing a continued threat.

This research underscores the critical importance of persistent seed banks as a reservoir for dominant invaders, even after active management interventions. The molecular barcoding framework developed here offers a powerful tool for ongoing biosecurity and restoration efforts, not just in South Georgia but also in other vulnerable island ecosystems globally. It provides a robust method for monitoring invasive plant populations and informing future strategies to protect unique biodiversity under increasing environmental pressures.