Tourism disassembles patterns of co-occurrence and weakens responses to environmental conditions of spider communities on small lake islands
2010
Ulrich, W. | Zalewski, M. | Hajdamowicz, I. | Stańska, M. | Ciurzycki, W. | Tykarski, P.
The impact of disturbance on animal and plant assemblages has been described mainly in terms of aggregate community properties like species richness, abundance, or productivity. However, the question how disturbance acts on species interactions, particularly on patterns of co-occurrence, has received much less attention. Here we use a large pitfall trap sample of spiders from two complexes of lake islands in Northern Poland to show how disturbance by tourist visits affects species richness, composition and co-occurrence. On the pristine and protected islands of Lake Wigry, species co-occurrence was significantly segregated. Further, island species richness and abundances could be predicted from environmental correlates, particularly from island area, soil fertility and humidity. In turn, on the lake islands that are frequently visited by tourists, species co-occurrences were random and environmental correlates other than island area failed to predict species richness and abundances. However, species composition, α-, β-, and γ-diversities, as well as average local spider abundances did not significantly differ between both island complexes. Our results show that disturbance disassembles the structure of spider communities prior to visible richness and abundance effects. This result has implications for biological conservation. The detection of community disassembly might be an early sign for factors that act negatively on ecosystem functioning.
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