title: Functional homogenization of flower visitor communities with urbanization.
abstract: Land-use intensification and resulting habitat loss are put forward as the main causes of flower visitor decline. However, the impact of urbanization, the prime driver of land-use intensification in Europe, is poorly studied. In particular, our understanding of whether and how it affects the composition and functioning of flower visitor assemblages is scant, yet required to cope with increasing urbanization worldwide. Here, we use a nation-wide dataset of plant-flower visitor (Coleoptera, Diptera, Hymenoptera, Lepidoptera) interactions sampled by citizen scientists following a standardized protocol to assess macroecological changes in richness and composition of flower visitor communities with urbanization. We measured the community composition by quantifying the relative occurrence of generalist and specialist flower visitors based on their specialisation on flowering plant families. We show that urbanization is associated with reduced flower visitor richness and a shift in community composition toward generalist insects, indicating a modification of the functional composition of communities. These results suggest that urbanization affects not only the richness of flower visitor assemblages but may also cause their large-scale functional homogenization. Future research should focus on designing measures to reconcile urban development with flower visitor conservation.
authors.affiliation: Department of Environmental Science, Policy, and Management University of California Berkeley California; MNHN-CNRS-UPMC UMR 7204 CESCO Muséum National d'Histoire Naturelle Paris France.
authors.forename: Nicolas
authors.initials: N
authors.lastname: Deguines
authors.affiliation: MNHN-CNRS-UPMC UMR 7204 CESCO Muséum National d'Histoire Naturelle Paris France.
authors.forename: Romain
authors.initials: R
authors.lastname: Julliard
authors.affiliation: Office Pour les Insectes et leur Environnement (OPIE) Guyancourt France.
authors.forename: Mathieu
authors.initials: M
authors.lastname: de Flores
authors.affiliation: MNHN-CNRS-UPMC UMR 7204 CESCO Muséum National d'Histoire Naturelle Paris France.
authors.forename: Colin
authors.initials: C
authors.lastname: Fontaine
keywords: Biotic homogenization; citizen science; flower visitor assemblages; macroecology; pollination; specialisation