Cataloging the alien flora of Portugal: New findings and updates

Abstract
During recent fieldwork in Portugal—mainly in the regions of Estremadura and Ribatejo in the autumn of 2024, but also earlier and elsewhere in the country—many interesting non-indigenous taxa were recorded. The following 25 taxa were not yet known from Portugal: Amaranthus blitum subsp. pseudogracilis, Amaranthus palmeri, Bassia indica, Cardiospermum grandiflorum, Casuarina cunninghamiana, Chloris gayana, Crepis bursifolia, Cyperus papyrus, Elatine ambigua, Eleocharis obtusa, Eragrostis mexicana, E. pectinacea, Guizotia abyssinica, G. schimperi, Hedera algeriensis, Hydrocotyle bowlesioides, H. sibthorpioides, Ipomoea hederacea, Megathyrsus maximus, Nassella tenuissima, Physalis angulata, Sida spinosa, Solanum bonariense, Vitis riparia and V. ×ruggerii. Among these, Hydrocotyle bowlesioides is particularly noteworthy as this record represents the first confirmed occurrence on the European mainland, extending the known non-native range of the species. In addition, several other taxa were recorded for the first time in particular regions, especially Estremadura and Ribatejo.
Most newly recorded species belong to Poaceae and Asteraceae, families that dominate alien floras in Mediterranean regions. Biogeographically, they originate mainly from tropical and subtropical America and Africa, reflecting both climatic affinity and strong anthropogenic dispersal. Regional analyses highlight contrasting patterns: Estremadura, with its urban and coastal environments, acts as a primary entry zone linked to horticultural and transport activities, whereas Ribatejo—especially along the Tagus valley—functions as a linear dispersal corridor for riparian and agricultural invaders. Several taxa are clearly naturalized, and some show local dominance, underlining an accelerating transition from casual to established status. These findings illustrate the ongoing dynamism of Portugal’s alien vascular flora under the combined influence of globalization, urbanization, and climate change, and emphasize the need for continued monitoring and documentation through coordinated fieldwork and digital biodiversity platforms, particularly in light of the high invasive potential demonstrated by many of the species involved.

Cite as
Verloove, F. & Alves, P (in press). Cataloging the alien flora of Portugal: New findings and updates. Perspectives in Biosecurity, 11(1).