Around the world in 500 years: Inter?regional spread of alien species over recent centuries

Aim The number of alien species has been increasing for centuries world-wide, but temporal changes in the dynamics their inter-regional spread remain unclear. Here, we analyse rate and extent over time how these vary among major taxonomic groups. Location Global. Time period 1500–2010. Major taxa studied Vascular plants, mammals, birds, fishes, arthropods other invertebrates. Methods Our analysis is based on Alien Species First Record Database, which comprises >60,000 entries describing year when an was first recorded a region (mostly countries large islands) where it later established as species. Based distribution records, calculated metrics between regions, termed “inter-regional spread”, conducted statistical analyses to assess variations across Results Almost all (>90%) introduced before 1700 are found more than one today. Inter-regional often took ongoing many intensity increased time, with particularly steep increases after 1800. Rates peaked plants late 19th century, birds invertebrates 20th remained largely constant mammals fishes. individual showed hump-shaped patterns, highest rates at intermediate range sizes. Approximately 50% widespread signs declines rates. Main conclusions results show that, although have declined species, entire groups they tended increase continuously time. numbers that currently observed only single anticipated be regions future.