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Bryon A. Daley from the University of Michigan, will be giving a seminar on Monday, May 22, as a part of the
NOAA & University of Michigan Great Lakes Seminar Series.

Please find details of his talk listed below.

Speaker: Bryon A. Daley, School of Natural Resources and Environment, University of Michigan, Ann Arbor

Title: Food web structure and the importance of species interactions in a Venezuelan stream

Date: Monday, May 22

Time: 3:00 PM

Location: Great Lakes Environmental Research Laboratory, 2205 Commonwealth Blvd., Ann Arbor, MI, 48105

Interactions among species can have important impacts on ecological processes, ranging from individual behavior to ecosystem function. However, there is a growing recognition that the importance of species interactions is context-dependent; organisms that are functionally important under one set of abiotic and biotic conditions may have little or no effect under another. Consequently, our ability to predict how changes in biodiversity will influence ecological processes depends on identifying factors underlying the importance of species interactions across space and taxa. Using a combination of descriptive and experimental approaches, I examined the direct and indirect effects of species interactions across riffle and run habitats in an Andean piedmont stream. In addition, I experimentally contrasted the relative effects of an herbivorous fish and a substantially smaller invertebrate grazer on algal and invertebrate assemblages. Specifically, I tested the prediction that large-bodied herbivores have a greater impact on algal and invertebrate assemblages compared to their smaller counterparts.

The direct and indirect effects of species interactions varied across habitats. Both the sedentary, invertebrate herbivore, /Petrophila /sp. (Pyralidae), and the grazing armored catfish, /Chaetostoma milesi/ (Loricariidae), significantly reduced algal biomass in riffles, but had no effect on algal biomass in runs. This variation was likely due to discrepancies in invertebrate settlement rates and differences in the composition of fish assemblages across habitats, as well as the different environmental conditions in the two habitats (e.g., water depth, current velocity, and dissolved oxygen concentration). Surprisingly, results of the second experiment did not support the prediction that large-bodied herbivores have a greater impact on algal and invertebrate assemblages relative to small-bodied herbivores. The effect of the invertebrate herbivore, /Petrophila /sp., on algal and invertebrate assemblages was equal to the effects of the grazing catfish, /Chaetostoma milesi/. In addition, /Petrophila /had a significantly greater per biomass effect on algal biomass compared to /Chaetostoma./

In an effort to reduce the impact of biodiversity loss on community and ecosystem processes, ecologists have stressed the importance of identifying strong interactors. Some authors have proposed that conservation efforts should focus on non-redundant species that perform essential ecosystem functions. Results from my experiments suggest that species interactions in a diverse stream system vary across habitats, and that an understanding of the biotic and abiotic contexts is important in identifying strong interactors. Furthermore, a full understanding of functional redundancy in natural systems may require an examination of a wider range of taxonomic and morphologically different species than is generally recognized.

If you have any questions or concerns, please email me at kanika.suri@noaa.gov; or call 734-741-2147.

For more information about the seminar series, please visit our website at http://www.glerl.noaa.gov/news/seminars/


Kanika Suri
Center of Excellence for Great Lakes and Human Health (CEGLHH)
2205 Commonwealth Blvd.
Ann Arbor, MI

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