"Dynamics of community assembly, disassembly, and reassembly in a neotropical floodplain river"

Essay by emiliojapHigh School, 12th gradeB+, January 2003

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The research seminar was about the Neotropical Floodplain River, a biogeography region of the New World that stretches southward from the Tropic of Cancer and includes southern Mexico, Central and South America, and the West Indies. Specifically, the study site was conduced in the most southern part of Venezuela; the Cinaruco River which contains an enormous variety of fish. Some examples of the fish living in the river are the "electric" fish, sling rays, cat fish, manati, caveman, and venezuelan crocodile.

The objective of the research was to evaluate the effects of the colonization rate on local community richness. There were seven beaches in the main channel and fish depended on environmental changes and its ecosystem. For example, the natural environment diversity of water level and fish stimulus changed from month to month. In January of 1999, the concentration of water is low, in May the water starts to rise, through July to September there is a high concentration of water and finally in November, the water starts to fall again.

The researcher found approximately 268 samples of fish and later he formulized his hypothesis that stated that the fish were randomly assembled. Later it was discovered that 97% of the fish were non-random and only 2 species (3%) were random therefore the hypothesis was not valid. Neotropical Floodplain Rivers are composed of local communities arranged around habitats of differing structural complexity and community structure was significantly assembled among environmental factors.

The researcher evaluated the rate of actual species in isolated local habitat patches and evaluated also the assemblage organization (co-occurrence patterns) as local patches are colonized. At the end, the total number of species collected from sixty five block samples was forty four fish and eight invertebrates.

The Standardized C-score in the research meant the number of chekered...