Biogeographical kinetics on an island volcano (Capelinhos, Azores): fast colonisation rates and dominance of arthropod exotic species

. 1. The aim of this paper was to investigate the arthropod colonisation of a recently erupted volcano in the framework of a general model of colonisation kinetics. 2. We analysed the diversity of arthropod communities at three locations on Faial Island (Azores) using a well-defined disturbance gradient: (i) a site that is new land added by the eruption of Capelinhos Volcano of 1957; (ii) a site moderately affected by this eruption; and (iii) a pristine site not affected. We calculated the recolonisation times at the disturbed sites using species richness at the undisturbed site as an equilibrium value (last erupted 9001000 years ago). 3. Species with different distributional ranges (endemic, native non-endemic and introduced) have different colonisation kinetics. Introduced exotic species were particularly rapid in colonising the erupted volcano, reaching a number of species greater than that observed in the undisturbed area. By contrast, native non-endemic species had more difficulty in recolonising the erupted area, and no endemic has reached it. The volcano community is dominated by a few species with high abundance and shows low richness and strong dominance in comparison with the undisturbed community. The moderately disturbed site supports a rich and well-balanced arthropod community. 4. Although the erupted volcano has a species richness even slightly higher than the undisturbed site, this is a consequence of the high colonisation ability of introduced species, and its arthropod community is strongly disharmonic.