Species pool structure determines the level of generalism of island parasitoid faunas

Geographical variations in biological diversity are known to be driven by a number of biotic and abiotic factors. These include environmental gradients (climate and habitat) and the physical characteristics of each site or region (e.g. area, isolation, habitat diversity and topographic and landscape heterogeneity), in addition to regional processes and historical events, which determine the characteristics and evolutionary history of the species present in the regional pool (e.g. Ricklefs, 1987, 2007; Rahbek & Graves, 2001; Hawkins et al., 2003; Hortal et al., 2008). However, most current knowledge on diversity gradients is based on the study of variations in species richness and, to a lesser extent, a few morphological and ecological Division of Biology, Imperial College London, Silwood Park Campus, Ascot, Berkshire SL5 7PY, UK, Departamento de Ciências Agrárias – CITA-A (Azorean Biodiversity Group), Universidade dos Açores, Rua Capitão João de Ávila, 9700-042 Angra do Heroı́smo, Portugal, Department of Entomology, Natural History Museum, Cromwell Road, London SW7 5BD, UK, Centre for Population Biology, Imperial College London, Silwood Park Campus, Ascot, Berkshire SL5 7PY, UK, Departamento de Biodiversidad y Biologı́a Evolutiva, Museo Nacional de Ciencias Naturales (CSIC), C/José Gutiérrez Abascal 2, 28006 Madrid, Spain