@article{GebertSteffan‐DewenterKronbachetal.2022,
  author    = {Gebert, Friederike and Steffan-Dewenter, Ingolf and Kronbach, Patrick and Peters, Marcell K.},
  title     = {The role of diversity, body size and climate in dung removal: A correlative and experimental approach},
  series = {Journal of Animal Ecology},
  volume    = {91},
  journal   = {Journal of Animal Ecology},
  number    = {11},
  doi       = {10.1111/1365-2656.13798},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-293907},
  pages     = {2181 -- 2191},
  year      = {2022},
  abstract  = {The mechanisms by which climatic changes influence ecosystem functions, that is, by a direct climatic control of ecosystem processes or by modifying richness and trait compositions of species communities, remain unresolved. This study is a contribution to this discourse by elucidating the linkages between climate, land use, biodiversity, body size and ecosystem functions. We disentangled direct climatic from biodiversity-mediated effects by using dung removal by dung beetles as a model system and by combining correlative field data and exclosure experiments along an extensive elevational gradient on Mt. Kilimanjaro, Tanzania. Dung removal declined with increasing elevation, being associated with a strong reduction in the richness and body size traits of dung beetle communities. Climate influenced dung removal rates by modifying biodiversity rather than by direct effects. The biodiversity-ecosystem effect was driven by a change in the mean body size of dung beetles. Dung removal rates were strongly reduced when large dung beetles were experimentally excluded. This study underscores that climate influences ecosystem functions mainly by modifying biodiversity and underpins the important role of body size for dung removal.},
  language  = {en}
}
@article{KohlSteffan‐Dewenter2022,
  author    = {Kohl, Patrick L. and Steffan-Dewenter, Ingolf},
  title     = {Nectar robbing rather than pollinator availability constrains reproduction of a bee-flowered plant at high elevations},
  series = {Ecosphere},
  volume    = {13},
  journal   = {Ecosphere},
  number    = {6},
  doi       = {10.1002/ecs2.4077},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-287141},
  year      = {2022},
  abstract  = {Abiotic factors are generally assumed to determine whether species can exist at the extreme ends of environmental gradients, for example, at high elevations, whereas the role of biotic interactions is less clear. On temperate mountains, insect-pollinated plant species with bilaterally symmetrical flowers exhibit a parallel elevational decline in species richness and abundance with bees. This suggests that the lack of mutualistic interaction partners sets the elevational range limits of plants via a reduction in reproductive success. We used the bee-pollinated mountain plant Clinopodium alpinum (Lamiaceae), which blooms along a continuous 1000-m elevational gradient and has bilaterally symmetrical flowers, as a model to test the predicted parallel elevational decline in flower visitation and seed production. Although the community of flower visitors changed with elevation, the flower visitation rate by the most frequent visitors, bumble bees (33.8\% of legitimate visits), and the overall rate of flower visitation by potential pollinators did not vary significantly with elevation. However, we discovered that nectar robbing by bumble bees and nectar theft by ants, two interactions with potentially negative effects on flowers, sharply increased with elevation. Seed set depended on pollinators across elevations and followed a weak hump-shaped pattern, peaking at mid-elevations and decreasing by about 20\% toward both elevational range edges. Considering the mid- and high elevations, elevational variation in seed production could not be explained by legitimate bee visitation rates but was inversely correlated with the frequency of nectar robbing. Our observations challenge the hypothesis that a decrease in the availability of pollinators limits seed production of bee-flowered plants at high elevations but suggest that an increase in negative interactions (nectar robbing and larceny) constrains reproductive success.},
  language  = {en}
}