BackgroundWild 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.Methodology/Principal FindingsOver 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/SignificanceWe 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.

Most bees display an array of strategies for building their nests, and the availability of nesting resources plays a significant role in organizing bee communities. Although urbanization can cause local species extinction, many bee species persist in urbanized areas. We studied the response of a bee community to winter-installed humanmade nesting structures (bee hotels and soil squares, i.e. 0.5 m deep holes filled with soil) in urbanized sites. We investigated the colonization pattern of these structures over two consecutive years to evaluate the effect of age and the type of substrates (e.g. logs, stems) provided on colonization. Overall, we collected 54 species. In the hotels, two gregarious species, Osmia bicornis L. and O. cornuta Latr. dominated the community (over 87 % of the data). Over 2 years, the age of the soil squares did not affect their level of colonization and the same was true for the hotels with respect to O. bicornis and 'other species'. However, O. cornuta occurred less often and raised fewer descendants in 1-year old hotels than in new ones. Bee nesting was not affected by the soil texture and, among above-ground nesting bees, only O. bicornis showed a preference for some substrates, namely Acer sp. and Catalpa sp. In a context of increasing urbanization and declining bee populations, much attention has focused upon improving the floral resources available for bees, while little effort has been paid to nesting resources. Our results indicate that, in addition to floral availability, nesting resources should be taken into account in the development of urban green areas to promote a diverse bee community. Keywords Wild bees Á Nesting resource availability Á Nest-site fidelity Á Phylopatry Á Nest-site selection Á Substrate quality Á Human-made nesting structures Á Urban area This work is dedicated in memoriam of Robert Fonfria.

Establishment of a bee collection (Hymenoptera, Apoidea) as part of a biodiversity study. In the framework of the European ALARM project, we used sampling methods to assess pollinator diversity (bees and syrphid flies) and abondance, and therefore started reference collections. Identification required killing, pinning, and adequate preparation of the insects sampled. We present a set of guidelines for the preparation of bee specimens and a protocol for processing specimens caught in liquid media. We also provide recommendations to fill out labels for collection purposes. Finally, we suggest some techniques that can help keeping a well-curated bee collection.

Wild bees are declining, mainly due to the expansion of urban habitats that have led to land-use changes. Effects of urbanization on wild bee communities are still unclear, as shown by contrasting reports on their species and functional diversities in urban habitats. To address this current controversy, we built a large dataset, merging 16 surveys carried out in 3 countries of Western Europe during the past decades, and tested whether urbanization influences local wild bee taxonomic and functional community composition. These surveys encompassed a range of urbanization levels, that were quantified using two complementary metrics: the proportion of impervious surfaces and the human population density. Urban expansion, when measured as a proportion of impervious surfaces, but not as human population density, was significantly and negatively correlated with wild bee community species richness. Taxonomic dissimilarity of the bee community was independent of both urbanization metrics. However, occurrence rates of functional traits revealed significant differences between lightly and highly urbanized communities, for both urbanization metrics. With higher human population density, probabilities of occurrence of above-ground nesters, generalist and small species increased. With higher soil sealing, probabilities of occurrence of above-ground nesters, generalists and social bees increased as well. Overall, these results, based on a large European dataset, suggest that urbanization can have negative impacts on wild bee diversity. They further identify some traits favored in urban environments, showing that several wild bee species can thrive in cities.

Depuis plusieurs centaines de millions d'années, les insectes et les plantes entretiennent d'étroites relations ; avec l'apparition des fleurs, les butineurs se sont grandement diversifiés et jouent un rôle important dans le transport du pollen. Cette co-évolution est maximale entre les abeilles et les plantes à fleurs, dont l'activité de nourrissage des unes dépend la pollinisation des autres. Le terme «abeilles» correspond aux Apoidea Apiformis, représentés par près de 1000 espèces en France, dont une seule est élevée dans les ruches. Or le déclin des pollinisateurs qui touche de plein fouet les abeilles sauvages et domestiques est de plus en plus préoccupant. La majorité de nos plantes sauvages et cultivées dépendent, pour leur reproduction, de l'activité pollinisatrice des insectes et particulièrement des abeilles. Aussi, la faune d'abeilles de Rhône-Alpes et de France est encore largement méconnue, faute de références et de spécialistes... Il est pourtant nécessaire de faire progresser nos connaissances, pour mieux comprendre et appréhender les impacts anthropiques, et limiter cette perte préoccupante du vivant. Cet article tente de donner sommairement les premiers éléments pour entrer dans le vaste monde des abeilles.