GLIN==> UPCOMING SEMINAR

[Kanika Suri <Kanika.Suri@noaa.gov>]

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

Abstract:
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
48105

734-741-2147
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