Body size and biomass distributions of carrion visiting beetles: do cities host smaller species?

The question how animal body size changes
along urban–rural gradients has received much attention
from carabidologists, who noticed that cities harbour
smaller species than natural sites. For Carabidae this
pattern is frequently connected with increasing disturbance
regimes towards cities, which favour smaller
winged species of higher dispersal ability. However,
whether changes in body size distributions can be generalised
and whether common patterns exist are largely
unknown. Here we report on body size distributions of
carcass-visiting beetles along an urban–rural gradient in
northern Poland. Based on samplings of 58 necrophages
and 43 predatory beetle species, mainly of the families
Catopidae, Silphidae, and Staphylinidae, we found
contrary patterns of necrophages and predatory beetles.
Body sizes of necrophages decreased towards the city
centre and those of predators remained unchanged.
Small necrophages and large predators dominated in
abundance in the city centre. Necrophage body sizes
appeared to be more regularly spaced in the city centre
than expected from a random null model and in comparison
to the rural pattern, pointing to increased
competition.