Universität zu Köln

Biermann, Erich (2014). Arthropod food-webs on man-made lake islands. PhD thesis, Universität zu Köln.

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Abstract

Food webs are the dynamic structure of natural ecosystems. Island biogeographical and meta-community perspectives have aided food web research in spatially delimiting and opening the the studied object at the same time. While islands and habitat fragments have become empirical representations of spatially delimited focal habitat patches and their dynamics, considering the dispersal of organisms between them has opened new perspectives on community assembly and the maintenance of biodiversity. Furthermore, the spillover of organisms between adjacent habitats has been integrated into studying the dynamics of local ecosystem processes. These ‘spatial subsidies’ can generate strong interdependencies between the food webs of adjoined habitats, as different as terrestrial and aquatic ones. When studying the effects of ecosystem size and spatial subsidies on community and food web properties, islands have a prominent role in testing appropriate ecological hypotheses. In this study, the effect of ecosystem size in determining the food chain length of arthropod communities was investigated on young man-made lake islands of restored lakes in the Lower Rhine area. Moreover, it was analyzed how the importance of spatial subsidies for local food webs varied with island area and which role dispersal and adaptations to local conditions have in determining the community composition of large and small islands. Food chain length and spatial subsidies were tracked with a stable isotope approach. A strong relationship between food chain length and island area could be shown, while the importance of spatial subsidies, which was restricted to a few species, decreased with island size. It could be shown, that the species richness of spiders and ground beetles tracked an increasing spatial heterogeneity with increasing island size and arthropods were significantly assorted to spatially varying environmental conditions.