Non-native species in the vascular flora of highlands and mountains of Iceland

The highlands and mountains of Iceland (defined here as areas located above 400 m a.s.l) are one of the largest remaining wilderness areas in Europe. The present study provides the first comprehensive and up-to-date data on non-native plant species from these wilderness areas. Overall, 16 non-native vascular plant specieswere detected, including 11 casuals and 5 naturalised taxa (1 invasive). Results showed that the central highlands are most vulnerable to non-native plant colonisation, while other mountain and highland areas in Iceland seem to be far less impacted by non-native plants. Clear hotspots of alien flora are evident, especially in popular tourist areas in the highlands and mountains such as hot springs, geothermal areas, mountain huts and shelters, as well as main roads and tracks. Temporal trends characterizing non-native plant colonization show that the process is still in its initial phase. This research suggests that human-mediated dispersal is the main driving force increasing the risk of invasion in Icelandic highlands and mountain areas.