Data from: Urban bumblebees are smaller and more phenotypically diverse than their rural counterparts

1. With urbanization identified as being one of the key drivers of change
in global land use, and the rapid expansion of urban areas worldwide, it
is relevant to evaluate how novel ecological conditions in cities shape
species functional traits, which are essential for how species interact
with their environments and with each other. 2. Despite the many
comparative studies on organisms living in urban and non-urban areas our
knowledge on species responses to urban environments remains limited. For
one, much of the ecological research has assumed that the environment
changes in a linear fashion from the city core to the city edges, whereas
in reality the environments within the cities are highly heterogeneous.
Furthermore, studies on species responses to these highly variable
ecosystems are often based on interspecific mean trait values, which
ignore the potential for high levels of intraspecific variation among
individuals in key functional traits. 3. The current study investigated
intraspecific functional trait differences for four functional traits
associated with body size, mobility, and resource selection among rural
and urban populations of two common bumblebee species, Bombus pascuorum
and Bombus lapidarius, in urban centers and adjacent rural areas in
Switzerland. 4. We document shifts in functional traits towards smaller
individuals and higher multidimensional trait variation in urban
populations compared to rural conspecifics of both species. This shows
that urban individuals for both species are on average smaller sized but
populations are distinctively different from rural population by
increasing their trait richness and diversifying their trait combinations.
In addition, we found bimodality in tongue length within urban B.
pascuorum populations. 5. Our results suggest that urban and rural
populations possibly experience differential selection pressures resulting
in trait differences across and among populations. We argue that
variations in the respective foraging landscapes in cities leads to
smaller-sized but phenotypically more diverse populations, and drive
functional trait divergence.