Tuesday, May 19, 2009
230

Species loss and exotic introduction: Effects on ecosystem function

Susanna E. Scott, Corey Pray, Weston H. Nowlin, and Yixin Zhang. Department of Biology, Texas State University, 601 University Drive, San Marcos, TX 78666

Biodiversity and ecosystem functioning are closely linked to determine community dynamics and species interactions. The loss or addition of species to a community can have substantial impacts on ecosystem functions including production, respiration, nutrient retention, and decomposition. We hypothesized that native and non-native consumers differently influence ecosystem processes and benthic community assemblages via biotic and abiotic interactions. To test this hypothesis, we performed a 2 x 2 factorial experiment using Macrobrachium carcinus (Decapoda: Palemoides), a native species whose population is declining, and the non-native armored sucker-mouth catfish (Hypostomus sp., Loricariidae), as our model species. These experiments were performed in artificial stream channels designed to mimic conditions in the San Marcos River, Texas.  Hypostomus catfishes showed a significant influence on ecosystem functioning by decreasing periphyton abundance and facilitating leaf breakdown.  Presence of Hypostomus sp. reduced collector gatherer abundances in leaf packs and produced ecosystem engineering effects by increasing sediment movement through the benthos. Macrobrachium carcinus decreased periphyton concentration on tiles, and interfered with periphyton consumption by Hypostomus. Invasive species pose a critical threat to aquatic ecosystems by significantly impacting community structure and ecosystem functioning. This study shows that invasive Hypostomus catfishes can alter biodiversity and ecosystem processes in the experimental streams.


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