Global Expansion of Ponto‐Caspian Aquatic Invaders: Drivers, Trends and Taxonomic Biases in a Changing World

Biological invasions pose major threats to ecosystems, with aquatic habitats particularly vulnerable due to high connectivity and biodiversity. The Ponto‐Caspian region is widely recognised as a major source of highly invasive non‐native aquatic species, yet a global synthesis of their spatial, taxonomic and temporal invasion patterns has been lacking. Here, we provide the first global review of the taxonomic diversity of non‐native aquatic Ponto‐Caspian species from published literature and biodiversity records, including information on invasion pathways, spatial distribution and temporal reporting trends. Our analysis of 146 non‐native aquatic Ponto‐Caspian species revealed a strong taxonomic bias, with arthropods (53%) and fishes (23%) accounting for over three‐quarters of recorded taxa, while crustaceans (Malacostraca) were markedly over‐represented relative to global non‐native aquatic taxa. Canal‐mediated connectivity among European waterbodies remained the dominant invasion pathway, whereas ballast water has been the primary pathway to North America. Geographically, invasions were concentrated in Europe and the Laurentian Great Lakes, with few records from other continents. From a temporal perspective, reporting showed fluctuating trends associated with canal construction, management actions and growing scientific attention. Overall, our findings suggest that invasion risks from Ponto‐Caspian species are largely context‐dependent, mainly affecting Europe and North America, but increasing trends highlight the need for strengthened prevention, control and international cooperation under ongoing environmental change.