Patterns and drivers of range filling of alien mammals in Europe

Biological invasions are major drivers of biodiversity change. Alien mammals are par-ticularly concerning in Europe, where their expansion remains unabated, though thedriving factors are still unclear. Well-documented introductions and distributions inthis continent provide a unique opportunity to understand how human activities influ-enced this expansion. We modelled the potential alien ranges of 46 established alienmammals in Europe using species’ introduction localities, residence time, dispersalability, generation length and climatic suitability. We compared potential and observedranges through three range indices: range filling (portion of potential distributionoccupied), overfilling (portion of observed distribution unexpectedly occupied), andunfilling (portion of potential distribution currently unoccupied), and we investigatedthe effects of native range size, introduction pathways (species’ sum of the knownpathways of introduction across the European alien range, spanning 1492–2020), andsocio-economic variables (spanning 1980–2017) on uncovered patterns. We show thatthe median range overfilling value was high (22%), suggesting that alien mammals aresubstantially spreading outside expected distribution areas. Conversely, median valuesof range filling (14%) and unfilling (17%) were lower, suggesting recorded introduc-tions inadequately explain alien mammals’ distributions. Range patterns were stronglyshaped by human population density, which positively influenced all three range indi-ces, driving range patterns and influencing alien mammals’ introduction and establish-ment. In contrast, roads and railways were negatively related to range overfilling andunfilling, as was the number of introduction pathways to range filling and overfill-ing. Ultimately, the role of these socio-economic factors depends on human behav-iour rather than environmental characteristics or species’ ecology. We confirm human agency as an important driver of alien mammals’ distribution and spread in Europe, highlighting that modifying humanattitudes and regulations towards these taxa is key to limiting further spread.

Keywords

Biological invasions Introduction pathways Mammals, potential range Propagule pressure Range filling Socio-economic variables

URI

http://hdl.handle.net/10400.5/102499

Citation

Tedeschi, L., Lenzner, B., Schertler, A., Wessely, J., Biancolini, D., Capinha, C., Melone, B., Soria, C.D., Rondinini, C. & Essl, F. (2025), Patterns and drivers of range filling of alien mammals in Europe. Oikos, [online first], e11388. https://doi.org/10.1002/oik.11388