EPPO Global Database

EPPO Reporting Service no. 03 - 2023 Num. article: 2023/074

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