Mountains on oceanic islands offer unique opportunities to contribute to global understanding of native and non-native species range expansions due to their island-specific attributes, such as isolation, small area, confined species pool, low species richness, high endemicity, and relative youth. Altitudinal gradients on islands differ from those on mainlands by e.g. precipitation pattern and distribution of anthropogenic settlement. Currently, mountains on islands are observed to experience increasing rates of colonization by invasive species and rapid spread. Here, we present plant species diversity patterns (richness of endemic, native and alien plants, recorded following the global MIREN protocol) on roadsides, trailsides and in native vegetation along with microclimate, soil temperature and soil moisture data. Our data represents four elevation gradients, covering each aspect of the cone-shaped mountain, tradewind effected versus dry, from sea-level up to 2300 m a.s.l. in La Palma (Canary Islands, Spain). We evaluate the effect of elevation (macroclimate and ecosystem type) as well as microclimate offset (between native vegetation and anthropogenic disturbance) on species distributions and range size dynamics, thereby integrating data from 3 field-resurveys since 2013. Our findings suggest that alien species richness peaks at mid-elevation and is best explained by microclimate offset between disturbed and undisturbed habitat, while variation in native and endemic species richness is explained by macroclimatic pattern across elevation. However, contrary to expectations, community weighted specifc leaf area was lower at disturbed sites than in native vegetation, and generally highest at mid-elevation. Roads more so than trails contribute to the redistribution of non-native species along the elevational gradient.