Body size of ground beetles (Coleoptera: Carabidae) decreases with urbanization

Urbanization influences biodiversity and shapes the functional traits of local biota. While many cities expand, some have experienced significant population decreases resulting in an abundance of vacant greenspace following the demolition of residential structures. These vacant lots may provide suitable habitats for arthropods. Given habitat fragmentation in urban areas, The Equilibrium Theory of Island Biogeography (ETIB) can be applied to cities wherein rural areas act as mainlands and greenspaces within the city are islands surrounded by concrete that pose barriers to species movement. Within isolated greenspaces, ETIB predicts lower species richness due to colonization limitations. For arthropods such as ground beetles, dispersal ability is often related to body size, suggesting smaller species will be more likely to colonize urban islands because they are more commonly macropterous. This is important, as body size impacts fitness via female fecundity and male mating success, both of which typically increase with increased beetle size. We measured the body size of four species of ground beetles, Scarites vicinus, Poecilus lucublandus, P. chalcites, and Chlaenius tricolor across 40 greenspaces in Cleveland, OH, USA, and surrounding Cuyahoga County, to test whether urbanization poses barriers to carabid assemblages. We applied a functional trait-based approach to ETIB, predicting body size would decrease with increased isolation from rural surroundings. Specimens were collected using unbaited pitfall traps in five treatments including vacant lots mown monthly, urban pocket prairies seeded with wildflowers, urban and rural agroecosystems, and metro park forests. Preliminary results from June 2018 revealed clear habitat associations for these abundant carabid species, suggesting their populations are not ubiquitous among urban and rural greenspaces, although all were capable of flight. Body size of beetles was greater in rural environments, as the larger species S. vicinus and P. lucublandus were abundant in ...