Effect of urbanization on vegetation-dwelling spiders in the Nagyerdő Forest, in Debrecen City, Hungary
Abstract
The effect of urbanization on vegetation-dwelling spider assemblages was studied along a ruralsuburban-urban forest gradient in Debrecen city and in the neighboring Forest Reserve Area. Sweepnetting was used for the collecting of spiders from the middle of April to the end of October in every fourth week. The following hypotheses were tested: increasing disturbance hypothesis (species richness is decreasing by disturbance), matrix species hypothesis (the richness of open-habitat species is increasing by disturbance), opportunistic species hypothesis (the richness of generalist species is increasing by disturbance), and habitat specialist hypothesis (the number of the forest specialist species is decreasing by disturbance). Urban forest patches were usually drier and more open than rural and suburban ones; because of the park management the shrub and herb layer were sparse. It was assumed that the number of xerophilous and light-preferring species is increasing from the rural sites towards the urban ones, and the number of web-building species is decreasing along the gradient. Our findings revealed that the overall species richness decreased significantly towards the urban habitat, supporting the increasing disturbance hypothesis. Both the matrix and opportunistic species hypotheses failed, as the number of open-habitat species was the lowest in the suburban sites and the number of generalist species was higher in the rural habitat, than in the urban and in the suburban ones. Species richness of the forest specialist spiders was significantly higher in the rural sites. The species richness of both the xerophilous and light-preferring species was the highest in the urban area, supporting the xerophilous and the light-preferring species hypotheses. The number of orbweaving species was the highest in the rural area supporting the web-building species hypothesis.
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