Side effects of urbanization such as habitat fragmentation and ensuing edge effects lead to loss of biodiversity and weakening of important functional groups such as decomposers in urban and sub-urban natural communities. A recurring question is how resistant to the effects of urbanization the species composing functional groups are, and what factors, if any, mitigate changes caused by urbanization. We studied the effects of urbanization on carrion beetles (silphids) that use small vertebrate carcasses for feeding and reproduction, thus providing the important ecosystem service of carrion removal and recycling. In particular we asked how regional land use and differences in soil characteristics, such as soil moisture, compaction, or composition, affected silphid abundances in multiple natural areas along an urban-rural gradient. We specified 12 sampling sites with different land uses by drawing a 1km diameter square around multiple sites and estimating amount of developed, residential, and undeveloped area within. We then sampled silphids at each site over a four week period in July of 2016 using non-lethal pitfall traps and concurrently sampling multiple soil metrics such as compaction, moisture, and composition.
Results/Conclusions
We found that silphid abundance decreases from less developed rural sites to more developed urban sites although residential sites with intermediate levels of development did not have intermediate abundances of silphids. Soil characteristics were either not correlated to abundance (composition, percent gravel) or weakly correlated (temperature, compaction) partly because of high variation between sites within a particular land use category. The strongest correlation to silphid abundance came from the amount of permeable (i.e. unpaved/not built on) land surface available to silphids within a 1km area around a sampling site; suggesting that although soil characteristic may play a role in silphid habitat choice and abundance these are overshadowed by regional availability of suitable habitat.