Vallisneria spiralis and Egeria densa (Hydrocharitaceae) in arctic and subarctic Iceland

Abstract

Abstract We report the spread of two aquatic invasive plants, Vallisneria spiralis L. and Egeria densa Planch., into geothermal ponds in Iceland. These species are effective invaders due to their efficient dispersal, vegetative reproduction, high biomass production, and popularity in the aquarium trade. V. spiralis and E. densa were found in 2013 in a man-made pond near Husavik in northern Iceland. E. densa also occurs, at least since 2004, in southern Iceland, in Opnur Springs. Both species were confirmed by DNA sequencing. Our results indicate that V. spiralis and E. densa have established self-sustaining populations in Iceland, representing to date the northern-most confirmed occurrences of both species. These Icelandic populations extend the northern limit of E.densa and V. spiralis by at least 1000 km and, to our knowledge, are the first records of non-native invasive aquatic plants in the arctic and subarctic. Our study shows that geothermally heated water bodies can further facilitate the spread of aquatic invasive plants into arctic and subarctic areas.