The Impact of Stream Modification on the Distribution of Riverine Turtles in Iowa
VanDeWalle, Terry J.
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Comparisons were made of turtle populations in Red Rock Reservoir, the Des Moines River, and other rivers of the Mississippi River drainage system in Iowa. In addition, comparisons were made of turtle populations in rivers of the Missouri River drainage system in Iowa. Of the inland rivers of the Mississippi drainage examined in this study, the Des Moines River has undergone the greatest amount of modification. Number of turtle species ranged from five in the Des Moines River to 11 in the Mississippi River, but only three species were found in Red Rock Reservoir. In the Missouri drainage, number of turtle species ranged from three in both the Little Sioux and Nishnabotna rivers to five in the Missouri River. Stream modification appears to lower the diversity of riverine turtles by eliminating intolerant species. The mechanism for this elimination is probably a reduction in habitat diversity, creating a more uniform and simplified environment. False map (Graptemys pseudogeographica), smooth soft-shell (Trionyx muticus), and Blanding's turtles (Emydoidea blandingi) appear to be most affected by modification. Turtle diversity was lower in Red Rock Reservoir than in the Des Moines River, possibly due to the great fluctuation in the water level of the reservoir.
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