Document Type



Vertebrates, Community Ecology, Ecosystem Simplification, Coralville Reservoir in Iowa, Cone Marsh in Iowa


The vertebrates in communities comprising a habitat with unpredictable water levels (the Coralville Reservoir) were compared to those present in communities comprising a habitat without severely fluctuating water levels (Cone Marsh). From data on the species of vertebrates and their relative abundance, it was determined that extensive ecosystem simplification had occurred in communities along the Coralville Reservoir. The major characteristics of this simplification were the following: 1) several species with similar modes of feeding were present at Cone Marsh but only species with generalized food habits were present along the Coralville Reservoir; 2) species at the top of food chains often were very rare or absent in communities along the Coralville Reservoir flood plain, and 3) food chains that were dominant at Cone Marsh often were less important on the Coralville Reservoir flood plain. On these characteristics is based the following hypothesis of ecosystem simplification: 1) a massive trophic simplification and reduction in the number of species present; 2) alterations in the trophic structure so that major food chains are different; 3) the replacement of specialized species by more generalized species capable of adapting to the environmental stresses imposed; and 4) severe reductions in, or elimination of, top trophic levels, which eliminates a mechanism for binding together communities in the same habitat.

Publication Date

September 1973

Journal Title

Proceedings of the Iowa Academy of Science





First Page


Last Page



©1973 Iowa Academy of Science, Inc.



File Format




To view the content in your browser, please download Adobe Reader or, alternately,
you may Download the file to your hard drive.

NOTE: The latest versions of Adobe Reader do not support viewing PDF files within Firefox on Mac OS and if you are using a modern (Intel) Mac, there is no official plugin for viewing PDF files within the browser window.