Differences in flower visitation networks between an oceanic and a continental island

Abstract

Two important biological differences between oceanic and continental islands are that the former usually have lower species richness and a higher degree of taxonomic disharmony than the latter. Although there is some evidence of less complex interaction networks on oceanic islands, only a few studies have compared island communities with each other or with mainland communities. Here, we analyse the species composition and structural properties of quantitative flower visitation networks in two communities of each of two different island systems: the Canary Islands (oceanic origin) and the Balearic Islands (continental origin). We compared different network parameters to inform us about their vulnerability in the face of different types of disturbance. The number of species was greater in the Balearic than in the Canarian networks but, contrary to expectations, the total number and diversity of interactions did not differ between them. Moreover, a greater number of opportunistic species and the presence of super-generalist species on the oceanic island led to significantly higher values of quantitative connectance and nestedness relative to those on the continental island. Given that these two parameters are associated with network stability, our findings support the hypothesis that oceanic island communities are less vulnerable to perturbations than are those of continental islands, although further studies with a network approach are needed to determine whether this is a general pattern. © 2014 The Linnean Society of London.