@article{CorneliusLeingaertnerHoissetal.2013,
  author    = {Cornelius, Christine and Leing{\"a}rtner, Annette and Hoiss, Bernhard and Krauss, Jochen and Steffan-Dewenter, Ingolf and Menzel, Annette},
  title     = {Phenological response of grassland species to manipulative snowmelt and drought along an altitudinal gradient},
  series = {Journal of Experimental Botany},
  volume    = {64},
  journal   = {Journal of Experimental Botany},
  number    = {1},
  doi       = {10.1093/jxb/ers321},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-126888},
  pages     = {241-251},
  year      = {2013},
  abstract  = {Plant communities in the European Alps are assumed to be highly affected by climate change, as the temperature rise in this region is above the global average. It is predicted that higher temperatures will lead to advanced snowmelt dates and that the number of extreme weather events will increase. The aims of this study were to determine the impacts of extreme climatic events on flower phenology and to assess whether those impacts differed between lower and higher altitudes. In 2010, an experiment simulating advanced and delayed snowmelt as well as a drought event was conducted along an altitudinal transect approximately every 250 m (600-2000 m above sea level) in the Berchtesgaden National Park, Germany. The study showed that flower phenology was strongly affected by altitude; however, there were few effects of the manipulative treatments on flowering. The effects of advanced snowmelt were significantly greater at higher than at lower sites, but no significant difference was found between both altitudinal bands for the other treatments. The response of flower phenology to temperature declined through the season and the length of flowering duration was not significantly influenced by treatments. The stronger effect of advanced snowmelt at higher altitudes may be a response to differences in treatment intensity across the gradient. Consequently, shifts in the date of snowmelt due to global warming may affect species more at higher than at lower altitudes, as changes may be more pronounced at higher altitudes. These data indicate a rather low risk of drought events on flowering phenology in the Bavarian Alps.},
  language  = {en}
}
@article{HolzschuhDormannTscharntkeetal.2013,
  author    = {Holzschuh, Andrea and Dormann, Carsten F. and Tscharntke, Teja and Steffan-Dewenter, Ingolf},
  title     = {Mass-flowering crops enhance wild bee abundance},
  series = {Oecologia},
  volume    = {172},
  journal   = {Oecologia},
  number    = {2},
  doi       = {10.1007/s00442-012-2515-5},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-132149},
  pages     = {477-484},
  year      = {2013},
  abstract  = {Although agricultural habitats can provide enormous amounts of food resources for pollinator species, links between agricultural and (semi-)natural habitats through dispersal and foraging movements have hardly been studied. In 67 study sites, we assessed the interactions between mass-flowering oilseed rape fields and semi-natural grasslands at different spatial scales, and their effects on the number of brood cells of a solitary cavity-nesting bee. The probability that the bee Osmia bicornis colonized trap nests in oilseed rape fields increased from 12 to 59 \% when grassland was nearby, compared to fields isolated from grassland. In grasslands, the number of brood cells of O. bicornis in trap nests was 55 \% higher when adjacent to oilseed rape compared to isolated grasslands. The percentage of oilseed rape pollen in the larval food was higher in oilseed rape fields and grasslands adjacent to oilseed rape than in isolated grasslands. In both oilseed rape fields and grasslands, the number of brood cells was positively correlated with the percentage of oilseed rape pollen in the larval food. We show that mass-flowering agricultural habitats—even when they are intensively managed—can strongly enhance the abundance of a solitary bee species nesting in nearby semi-natural habitats. Our results suggest that positive effects of agricultural habitats have been underestimated and might be very common (at least) for generalist species in landscapes consisting of a mixture of agricultural and semi-natural habitats. These effects might also have—so far overlooked—implications for interspecific competition and mutualistic interactions in semi-natural habitats.},
  language  = {en}
}
@article{HolzschuhDormannTscharntkeetal.2013,
  author    = {Holzschuh, Andrea and Dormann, Carsten F. and Tscharntke, Teja and Steffan-Dewenter, Ingolf},
  title     = {Mass-flowering crops enhance wild bee abundance},
  series = {Oecologia},
  volume    = {172},
  journal   = {Oecologia},
  number    = {2},
  doi       = {dx.doi.org/10.1007/s00442-012-2515-5},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-126852},
  pages     = {447-484},
  year      = {2013},
  abstract  = {Although agricultural habitats can provide enormous amounts of food resources for pollinator species, links between agricultural and (semi-)natural habitats through dispersal and foraging movements have hardly been studied. In 67 study sites, we assessed the interactions between mass-flowering oilseed rape fields and semi-natural grasslands at different spatial scales, and their effects on the number of brood cells of a solitary cavity-nesting bee. The probability that the bee Osmia bicornis colonized trap nests in oilseed rape fields increased from 12 to 59 \% when grassland was nearby, compared to fields isolated from grassland. In grasslands, the number of brood cells of O. bicornis in trap nests was 55 \% higher when adjacent to oilseed rape compared to isolated grasslands. The percentage of oilseed rape pollen in the larval food was higher in oilseed rape fields and grasslands adjacent to oilseed rape than in isolated grasslands. In both oilseed rape fields and grasslands, the number of brood cells was positively correlated with the percentage of oilseed rape pollen in the larval food. We show that mass-flowering agricultural habitats—even when they are intensively managed—can strongly enhance the abundance of a solitary bee species nesting in nearby semi-natural habitats. Our results suggest that positive effects of agricultural habitats have been underestimated and might be very common (at least) for generalist species in landscapes consisting of a mixture of agricultural and semi-natural habitats. These effects might also have—so far overlooked—implications for interspecific competition and mutualistic interactions in semi-natural habitats.},
  language  = {en}
}
@article{HendriksmaKuetingHaerteletal.2013,
  author    = {Hendriksma, Harmen P. and K{\"u}ting, Meike and H{\"a}rtel, Stephan and N{\"a}ther, Astrid and Dohrmann, Anja B. and Steffan-Dewenter, Ingolf and Tebbe, Christoph C.},
  title     = {Effect of Stacked Insecticidal Cry Proteins from Maize Pollen on Nurse Bees (Apis mellifera carnica) and Their Gut Bacteria},
  series = {PLoS ONE},
  volume    = {8},
  journal   = {PLoS ONE},
  number    = {3},
  doi       = {10.1371/journal.pone.0059589},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-131025},
  pages     = {e59589},
  year      = {2013},
  abstract  = {Honey bee pollination is a key ecosystem service to nature and agriculture. However, biosafety research on genetically modified crops rarely considers effects on nurse bees from intact colonies, even though they receive and primarily process the largest amount of pollen. The objective of this study was to analyze the response of nurse bees and their gut bacteria to pollen from Bt maize expressing three different insecticidal Cry proteins (Cry1A.105, Cry2Ab2, and Cry3Bb1). Naturally Cry proteins are produced by bacteria (Bacillus thuringiensis). Colonies of Apis mellifera carnica were kept during anthesis in flight cages on field plots with the Bt maize, two different conventionally bred maize varieties, and without cages, 1-km outside of the experimental maize field to allow ad libitum foraging to mixed pollen sources. During their 10-days life span, the consumption of Bt maize pollen had no effect on their survival rate, body weight and rates of pollen digestion compared to the conventional maize varieties. As indicated by ELISA-quantification of Cry1A.105 and Cry3Bb1, more than 98\% of the recombinant proteins were degraded. Bacterial population sizes in the gut were not affected by the genetic modification. Bt-maize, conventional varieties and mixed pollen sources selected for significantly different bacterial communities which were, however, composed of the same dominant members, including Proteobacteria in the midgut and Lactobacillus sp. and Bifidobacterium sp. in the hindgut. Surprisingly, Cry proteins from natural sources, most likely B. thuringiensis, were detected in bees with no exposure to Bt maize. The natural occurrence of Cry proteins and the lack of detectable effects on nurse bees and their gut bacteria give no indication for harmful effects of this Bt maize on nurse honey bees.},
  language  = {en}
}
@article{KellerGrimmerSteffanDewenter2013,
  author    = {Keller, Alexander and Grimmer, Gudrun and Steffan-Dewenter, Ingolf},
  title     = {Diverse Microbiota Identified in Whole Intact Nest Chambers of the Red Mason Bee Osmia bicornis (Linnaeus 1758)},
  series = {PLoS One},
  journal   = {PLoS One},
  doi       = {10.1371/journal.pone.0078296},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-97305},
  year      = {2013},
  abstract  = {Microbial activity is known to have profound impact on bee ecology and physiology, both by beneficial and pathogenic effects. Most information about such associations is available for colony-building organisms, and especially the honey bee. There, active manipulations through worker bees result in a restricted diversity of microbes present within the colony environment. Microbial diversity in solitary bee nests remains unstudied, although their larvae face a very different situation compared with social bees by growing up in isolated compartments. Here, we assessed the microbiota present in nests and pre-adults of Osmia bicornis, the red mason bee, by culture-independent pyrosequencing. We found high bacterial diversity not comparable with honey bee colonies. We identified a variety of bacteria potentially with positive or negative interactions for bee larvae. However, most of the other diverse bacteria present in the nests seem to originate from environmental sources through incorporated nest building material and stored pollen. This diversity of microorganisms may cause severe larval mortality and require specific physiological or symbiotic adaptations against microbial threats. They may however also profit from such a diverse environment through gain of mutualistic partners. We conclude that further studies of microbiota interaction in solitary bees will improve the understanding of fitness components and populations dynamics.},
  language  = {en}
}