Interactions between consumer and resource diversity under changing environmental conditions

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There has been a long debate whether producer diversity is controlled by the presence of consumers (top-down regulation) or by the availability of resources (bottom-up regulation). Only recently, syntheses on existing studies via meta-analyses suggested an interaction of both these factors in regulating producer diversity. This project investigates the role of consumer species diversity on the species diversity of a prey community. The effects of the consumers on the prey diversity are expected to not only depend on the diversity of the consumer community, but also on the species identity and feeding type of the consumers and other environmental factors. These potentially complex interactions between consumers and other environmental factors on the prey community will be investigated under controlled laboratory conditions and in mesocosm and field experiments using periphyton as resource community and freshwater benthic invertebrates (gastropods, isopods, trichoptera, ephemeroptera) as consumers. Furthermore, the diversity of the prey community is hypothesized to have impacts on the nutritional quality of the (mixed) prey assemblage for the consumers when different prey species contribute differently (with respect to important nutritional constituents) to the consumers’ diet. Since the nutritional quality of the resource often determines the trophic transfer efficiency in food webs, it is expected that more diverse prey assemblages enhance the trophic transfer efficiency and the productivity on the consumer level. Hence, this project combines important and fundamental questions on the relations between biodiversity and ecosystem structure with the innovative and new methodological approach of using molecular tools for the assessment of periphyton community diversity.