Raw data: Wildbee Monitoring along two elevational gradients in Germany

Global warming is assumed to restructure mountain insect communities in
space and time. Theory and observations along climate
gradients predict that insect abundance and richness, especially of
small-bodied species, will increase with increasing
temperature. However, the specific responses of single species to
rising temperatures, such as spatial range shifts, may weaken such
prediction, asking for intensive monitoring of real-world communities over
time. Here, we examined the temporal and spatial change in wild bee
communities and its drivers along two largely well-protected elevational
gradients (alpine grassland vs. prealpine forest), each resampled within
the last decade. Along both gradients, we detected clear upward shifts in
bee communities, with cold-adapted bumblebee
species reacting particularly sensitive, demonstrating the speed
with which mobile organisms can respond to climatic changes. Mean annual
temperature (MAT) was identified as the main driver of species richness in
both regions. Accordingly, and in large overlap with expectations under
climate warming, we detected an increase in bee richness and abundance,
and an increase of small-bodied species in low- and mid-elevations along
the grassland gradient. While changes in upward shifts, species richness,
abundance and body size in the prealpine forest gradient were partly
consistent with the alpine grassland system, they were generally weaker,
which could be due to a much less severe warming trend than in the alpine
grassland system or due to the variable and possibly confounding effect of
canopy cover. Our study highlights the use of accurate
assessed abundance data revealing rapid changes in bee communities over
only one decade. We conclude, that in well-protected temperate regions,
small-bodied bees may initially profit from warming temperatures, by
getting more abundant and diverse.