Molecular confirmation of Myriophyllum rubricaule in Great Britain
Myriophyllum rubricaule (Haloragaceae: EPPO Alert List) is an amphibious or aquatic species, with only female plants observed in the introduced range. It occurs in slow moving water bodies including rivers, irrigation channels, ponds, lakes, canals and damp ditches. Potential impacts are likely to be similar to that of M. aquaticum, although the plant is of more modest dimensions. Dense mats of M. rubricaule could block sunlight which may alter the quality of the water body by reducing oxygen levels. This can have a negative impact on invertebrates and plant species in the invaded habitat. Ecosystem services can be negatively affected, for example by reducing access to the water body or blocking irrigation channels.
In the EPPO region, M. rubricaule is known in Belgium and the Netherlands, where it has escaped from cultivation into the natural environment. It has also been reported from Hungary, and recent iNaturalist records provide locations for Austria, Denmark and Great Britain (EPPO RS 2025/162).
Molecular research was conducted to confirm the identity of field-collected plant samples in England and Wales, and a nursery in Scotland, resembling M. rubricaule. Phylogenetic analyses of the Myriophyllum samples using combined datasets of four regions (rDNA-ITS, rbcL, trnH-psbA and matK coding-region) and five regions (the rDNA-ITS, rbcL, trnH-psbA, trnK-matK and trnL-trnF) were undertaken using a maximum likelihood method. The results showed that two field-collected samples and one sample from an aquatic plant nursery were identical to M. rubricaule, confirming the occurrence of the species in the natural environment in Great Britain.
Sources
Kurose D, Tilling AE, Varia S, Pratt CF (2026) First report of field occurrence of Myriophyllum rubricaule in Great Britain confirmed through molecular analyses. CABI Agriculture and Bioscience 7(1), 0050. https://doi.org/10.1079/ab.2026.0050