Species abundance distributions (SADs) in different trophic groups across archipelagos

Abstract

The observation that ecological systems contain a small number of very abundant species and numerous relatively rare species is often described as one of only a few universal ecological laws. In this contribution we use standardized arthropod and vascular plant datasets from the Azores, Madeira, Canary Islands and La Reunion to investigate the impact island characteristics in species abundance distributions (SADs). We found that in Azores a large number of communities are bimodal, comprising very rare species (i.e. with low abundances) and relatively common species. Satellite taxa, introduced species and species that are more adapted to anthropogenic land surrounding the native forest tend to be found in lower abundances. More generally for all the archipelagos, we also found that SADs change as a function of species rarity and island age. In this respect, island identity is more important than trophic group in the properties of SADs. The consistent observed differences in the shape and parameters of island SAD models demonstrate that the study of relative species abundances is potentially useful in island biogeography