MadSci Network: Evolution

Re: Why fresh water life is common to all lakes yet separated by lots of land

Date: Mon Aug 17 11:58:46 1998
Posted By: Neala MacDonald, Grad Student, MSc in Zoology, University of Western Ontario
Area of science: Evolution
ID: 901520417.Ev


You have a very good, thoughtful question with heavy duty evolution! I had to consult with two benthic-oriented graduate students who study invertebratest for this answer (see signature for their names).

All/most of the freshwater lakes in North America were formed around the same geologic time (post glaciation), hence the fauna will tend to be macroscopically similar. Furthermore, very few lakes are completely isolated. Most are connected via streams/rivers, and flora and fauna can be transported with any current. Even if there is no perceived "real" connection, fauna in many life stages can be transported - for example by webbed duck feet, or on algae strands that are transported via other animals. On a more microscopic note (in terms of benthic creatures), these organisms rely on particular conditions (in terms of temp, O2, pH, substrate size, etc). Hence, if similar water conditions exist in several lakes (which tends to be the case in most eco-geographic regions), they will yield similar benthic communities.

Hope this helps.

- Iwona Ciesielka & Kellie White
Graduate Students of Ecology & Evolution
University of Western Ontario

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