title: Decreasing abundance, increasing diversity and changing structure of the wild bee community (Hymenoptera: Anthophila) along an urbanization gradient.
abstract: BACKGROUND
  Wild bees are important pollinators that have declined in diversity and abundance during the last decades. Habitat destruction and fragmentation associated with urbanization are reported as part of the main causes of this decline. Urbanization involves dramatic changes of the landscape, increasing the proportion of impervious surface while decreasing that of green areas. Few studies have investigated the effects of urbanization on bee communities. We assessed changes in the abundance, species richness, and composition of wild bee community along an urbanization gradient.
  
  
  RESULTS
  Over two years and on a monthly basis, bees were sampled with colored pan traps and insect nets at 24 sites located along an urbanization gradient. Landscape structure within three different radii was measured at each study site. We captured 291 wild bee species. The abundance of wild bees was negatively correlated with the proportion of impervious surface, while species richness reached a maximum at an intermediate (50%) proportion of impervious surface. The structure of the community changed along the urbanization gradient with more parasitic species in sites with an intermediate proportion of impervious surface. There were also greater numbers of cavity-nesting species and long-tongued species in sites with intermediate or higher proportion of impervious surface. However, urbanization had no effect on the occurrence of species depending on their social behavior or body size.
  
  
  CONCLUSIONS
  We found nearly a third of the wild bee fauna known from France in our study sites. Indeed, urban areas supported a diverse bee community, but sites with an intermediate level of urbanization were the most speciose ones, including greater proportion of parasitic species. The presence of a diverse array of bee species even in the most urbanized area makes these pollinators worthy of being a flagship group to raise the awareness of urban citizens about biodiversity.
authors.affiliation: INRA, UR 406 Abeilles et Environnement, Avignon, France.
authors.forename: Laura
authors.initials: L
authors.lastname: Fortel
authors.affiliation: INRA, UR 406 Abeilles et Environnement, Avignon, France; UMT Protection des Abeilles dans l'Environnement, Avignon, France.
authors.forename: Mickaël
authors.initials: M
authors.lastname: Henry
authors.affiliation: INRA, UR 406 Abeilles et Environnement, Avignon, France.
authors.forename: Laurent
authors.initials: L
authors.lastname: Guilbaud
authors.affiliation: INRA, UR 406 Abeilles et Environnement, Avignon, France.
authors.forename: Anne Laure
authors.initials: AL
authors.lastname: Guirao
authors.affiliation: Department of Life Sciences, Natural History Museum, London, United Kingdom.
authors.forename: Michael
authors.initials: M
authors.lastname: Kuhlmann
authors.affiliation: Arthropologia, Ecocentre du Lyonnais, La Tour de Salvagny, France.
authors.forename: Hugues
authors.initials: H
authors.lastname: Mouret
authors.affiliation: UMT Protection des Abeilles dans l'Environnement, Avignon, France; ACTA, Site Agroparc, Avignon, France.
authors.forename: Orianne
authors.initials: O
authors.lastname: Rollin
authors.affiliation: INRA, UR 406 Abeilles et Environnement, Avignon, France; UMT Protection des Abeilles dans l'Environnement, Avignon, France.
authors.forename: Bernard E
authors.initials: BE
authors.lastname: Vaissière
mesh_terms: D000818:Animals; D001516:Bees / Q000235:genetics / Q000502:physiology*; D044822:Biodiversity; D002947:Cities; D017753:Ecosystem; D005602:France; D016014:Linear Models; D011157:Population Dynamics; D013045:Species Specificity; D014507:Urbanization