Different levels of disturbance influence the distributional patterns of native but not exotic plant species on New Zealand small islands

Abstract

Disturbances of oceanic origin can severely affect plant communities on islands, but it is unclear whether they promote or deter biological invasions. Here, I collected floristic data from 97 small islands subject to different levels of ocean-borne disturbances (i.e. inside and outside Wellington Harbour, New Zealand). First, I tested how relationships between the richness of native and exotic species and island characteristics (e.g. area, isolation, height, distance from nearest dwelling) changed depending on island location. Next, I assessed compositional differences on inner and outer islands for both native and exotic species, and• While results for natives might reflect differences in disturbance levels, those for exotics may be related to lack of coastal specialists in the species pool, invasion timelags and non-equilibrium dynamics.