Abstract

Four Utah populations of Drosophila pseudoobscura from the Wasatch Mountains in Utah were sampled and characterized for third chromosome gene arrangements. The original samples in this area were taken in 1940 and 1950. At that time the populations were essentially monomorphic for the Arrowhead arrangement, with small percentages of Pikes Peak and Chiricahua also found. The current samples show these populations to contain eight third chromosome arrangements; seven previously described (AR, PP, CH, ST, TL, OL, EP) and a newly discovered endemic arrangement (American Fork, AF), with breakpoints 63E and 70D. The frequency of AR had decreased to 25% in certain areas; the highest frequency found being 63%. The observed array of arrangements is very similar to the Rocky Mountain populations of Colorado, and repeated sampling from one of the Utah localities seems to show a seasonal variation of the AR chromosome resembling that of the Colorado area. Due to the diversity and extent of the changes observed it is improbable that any one mechanism or event could account for these changes.

Degree

College and Department

Life Sciences; Plant and Wildlife Sciences

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