Diversity and assemblage filtering in ground-dwelling spiders (Araneae) along an urbanisation gradient in Denmark

Abstract

We studied the effects on spiders of a three-step rural-urban urbanisation gradient near a Danish town embedded in a historically forested landscape. Using pitfall traps set in forested habitat patches, we collected a total of 3075 adult spiders of 80 species; the habitats under different degrees of urbanisation had 45–47 species. We found support for Gray’s Increasing Disturbance Hypothesis: the species richness trap−1 was significantly higher in the rural habitat than in any other one, and decreased from the rural forest to forest fragments dominated by non-native trees in the urban park. The number of forest specialist species also decreased along the urbanisation gradient. Neither the presence of generalists nor light-preferring species increased under more urbanised conditions, but web builders and hygrophilous species were more species-rich in the rural habitat than elsewhere. Using indicator values, we identified Coelotes atropos, Walckenaeria corniculans, Walckenaeria cucullata, and Pachygnatha listeri as species linked to the rural and suburban habitats; Trochosa terricola, Saaristoa abnormis, Robertus lividus as characteristic of the rural habitat; and Gongylidium rufipes and Diplocephalus latifrons as urban habitat specialists.