Bark or crown? Spiders (Araneae) and beetles (Coleoptera) on trees in a city centre

Rapid urbanisation during the last century caused declines in species diversity. Cities encompass only a limited number of highly fragmented natural habitats and thus trees remain an important key factor for survival of local invertebrates. In 2021, we surveyed spider and beetle assemblages inhabiting trees in Pilsen city (Czech Republic). We selected 18 deciduous trees in the surroundings of the city centre and sampled bark species using corrugated cardboard bands, and crown species using a sweep net. The recorded species were evaluated using their functional traits such as habitat and humidity preferences, body size, and feeding guilds - i.e., the methods of spiders' feeding strategies. Altogether, we recorded 35 spider species/295 individuals, and 43 beetle species/265 individuals. We observed significant differences between the number of species and individuals inhabiting bark and tree crowns. Spiders tended to inhabit bark, while beetles inhabited tree crowns. The trees frequently contained species with different functional traits and with opposite requirements.