Does increasing density stress favour invasive Does increasing density stress favour invasive amphipod species in Central European streams? Evidence from a lab experiment

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Abstract

As globalisation and climate change progress, invasive species emerge as serious threat to regional diversity worldwide. Increasing water scarcity combined with decreasing resources including available space may promote invasion, resulting in density stress amongs populations. This hypothesis was applied to the amphipod Echonogammarus berilloni currently replacing the native G. pulex in Central European streams. In a laboratory experiment G. pulex populationsby creating three different density levels simulating low, moderate and high population density. The parameters locomotion, ingestion, glycogen content and mortality were analysed to detect a potential stress response in G. pulex. This was tested for G. pulex solely and for approaches with E. berilloni in a similar, smaller and greater individual number. The combination of both population density effects and the presence of E. berilloni demonstrated that G. pulex is actually affected by the invasive species. Increased activity, a reduced ingestion, higher mortality and a low glycogen content are the results. In populations with solely G. pulex an increased density level was observed to result in a reduction of activity and ingestion as well as in a high glycogen content indicating that G. pulex prefers moderate up to high population densities. Our findings conribute to explain possible reasons for the successful progression of E. berilloni, and species invasions in general.

Speakers from the University of Münster

Meyer, Elisabeth Irmgard	Department of Limnology
Riss, Hans-Wolfgang	Department of Limnology