Although biological invasions are a major component of global environmental change, with profound ecological and economic impacts, processes underlying the spatial patterns of invasive species are still not fully understood. Here, we describe a novel dissimilarity framework to analyse spatial patterns of species diversity, illustrated with alien plant invasions in Northern Portugal. We tested the hypothesis that patterns of alien invasive plant species richness and composition are differently affected by differences in climate, land use and landscape connectivity (geographic distance and objects that facilitate dispersal such as roads and rivers) between pairs of localities at the regional scale. Additionally, we tested the role of life strategies (C-S-R Grime classification) and residence time of alien species in driving such patterns. Results showed that dissimilarity in species richness was more influenced by environmental distance (particularly climate), whereas geographic distance was more important to explain composition. Only minor differences were found in the responses of the three C-S-R strategies. Some effect of residence time was found, but only for dissimilarity in species richness. Our findings suggest that environmental conditions (e.g. climate conditions) limit the number of alien species invading a given site, but the presence of dispersal corridors determines the paths of invasion and therefore the pool of species reaching each site. Therefore, alien species management should include the mitigation of dispersal pathways along linear infrastructures.