Abstract
Aim The continuous spread of invasive species is attributed to demographic processes and high dispersal rates. Both can change and evolve during range expansion, eventually accelerating spread dynamics. Here, we document such an accelerated spread for one of the most invasive spiders in Europe, the dwarf spider Mermessus trilobatus , and test whether dispersal, reproduction or competitive ability is at the source of this pattern. Location Europe. Time period 1981–2021. Major taxon studied Mermessus trilobatus (Arachnida: Araneae: Linyphiidae). Methods First, we collected records from 21 countries across Europe to document the speed of progression of the invasion front over the last 40 years. Second, we collected live individuals from populations in the longest and more recently invaded areas and compared the dispersal propensity of offspring raised under standardized conditions. Third, we compared the reproduction and competitive ability of females derived from the populations of long‐invaded areas against areas with more recent establishment. Results The progression of the invaded range increased from about 150 km in the 1980s to some 400 km between 2010 and 2020. Dispersal‐related behaviour was nearly twice as frequent in offspring from invasion front populations compared to the core area. By contrast, we found no differences in reproduction or competitive ability among the studied populations. Further, neither joint inheritance nor trade‐offs of dispersal, reproduction or competitive ability were identified. Main conclusion As high dispersal is recessively inherited in M. trilobatus , our results suggest that the accelerated invasion is due to the accumulation of dispersive but not more reproductive or competitive genotypes in newly colonized areas. Given the high climatic amplitude of the species in North America, we expect it to spread over the remaining parts of Europe and large parts of Asia in the coming decades. Accelerated range expansion through the evolution of dispersal behaviour could play a role in numerous arthropod invasions worldwide.