EPPO Global Database

Riparian invasive alien plants in Portugal

Continental Portugal harbors at least 3 314 vascular plant species, of which at least 772 are alien and 113 are listed as invasive species in the Portuguese law. To assess the current status of riparian invasive alien plant species in Portugal, data was collected between 2003 and 2006 in 404 sites located in 29 river basins in continental Portugal. The data was collected during field work for the implementation of the Water Framework Directive (EU). This data was compared to habitat variables from where the vegetation data were collected. Habitat variables included ecological features as well land use change. All data were entered into a model to predict the future distribution of riparian invasive alien plants in Portugal. A total of 960 plant species were found in riparian ecosystems of continental Portugal. In 382 sites, 97 alien species were found and of these 34 are invasive alien plant species (Table 1). The highest number of alien species found in a single site was 15, and the highest number of invasive alien species was 10. Of the 382 sites, invasive plants were recorded in 297 sites. Bidens frondosa (207 sites), Conyza bonariensis (131 sites) and Arundo donax (83 sites) were the most frequently recorded invasive alien plants. The model suggested that the species richness of invasive alien plant species is positively associated with the size of the upstream catchment and the percentage of urban areas. The model predicts that there is a higher diversity of invasive alien plant species in the central and northwestern, lowland, regions of continental Portugal. Low species richness values were predicted for river sections in inland regions, regions south of Lisbon, and for mountainous areas. The model predicts that for 43.1% of river sections of Continental Portugal there are one to two invasive plant species, for 11.5% there are three to five, and for 2.2% there are five or more invasive plant species. 

Table 1. Thirty-four invasive alien plant species identified on rivers in Portugal (EPPO List of IAP = EPPO List of Invasive Alien Plants)

Species	Family	EPPO status	Origin
Acacia dealbata	Fabaceae	EPPO List IAP	Australia
Acacia longifolia	Fabaceae		Australia
Acacia melanoxylon	Fabaceae		Australia
Acer negundo	Sapindaceae		N America
Ailanthus altissima	Simaroubaceae	EPPO List IAP	Asia
Amaranthus albus	Amaranthaceae		N America
Amaranthus blitoides	Amaranthaceae		Americas
Amaranthus blitum subsp. emarginatum	Amaranthaceae		Americas
Amaranthus hybridus	Amaranthaceae		Americas
Amaranthus powellii	Amaranthaceae		N & Central America
Amaranthus retroflexus	Amaranthaceae		N & Central America
Amaranthus viridis	Amaranthaceae		S & Central America
Arundo donax	Poaceae		Asia
Symphyotrichum squamatum	Asteraceae		S America
Azolla filiculoides	Salviniaceae	EPPO List IAP	Americas
Bidens frondosa	Asteraceae	Observation List	N America
Erigeron bonariensis	Asteraceae		Americas
Erigeron canadensis	Asteraceae		N America
Erigeron sumatrensis	Asteraceae	EPPO List IAP	S America
Cortaderia selloana	Poaceae	EPPO List IAP	S America
Datura stramonium	Solanaceae		N America
Pontederia crassipes	Pontederiaceae	EPPO A2 List	S America
Elodea canadensis	Hydrocharitaceae		N America
Erigeron karvinskianus	Asteraceae		Americas
Eryngium pandanifolium	Apiaceae		S America
Galinsoga parviflora	Asteraceae		Americas
Gleditsia triacanthos	Fabaceae		N America
Myriophyllum aquaticum	Haloragaceae	EPPO List IAP	S America
Nicotiana glauca	Solanaceae		S America
Oxalis pes-caprae	Oxalidaceae	EPPO List IAP	S Africa
Phytolacca americana	Phytolaccaceae		N America
Robinia pseudoacacia	Fabaceae		N America
Tradescantia fluminensis	Commelinaceae		S America

Sources

Pabst R, Dias FS, Borda-de-Água L, Rodríguez-González PM, Capinha C (2022) Assessing and predicting the distribution of riparian invasive plants in continental Portugal. Frontiers in Ecology and Evolution 10, 875578. https://doi.org/10.3389/fevo.2022.875578