Degree Type


Date of Award


Degree Name

Doctor of Philosophy




The breeding structure of natural populations is a consequence of mating patterns in subpopulations and the amount of gene flow among subpopulations. This dissertation is a study of seasonal changes in the breeding structure of natural populations of the house fly, Musca domestica L;Allozyme frequencies were estimated at nine enzymatic loci in flies collected for two years at six farms. Allozymes were resolved by vertical polyacrylamide gel electrophoresis. Allelic and genotypic frequencies were studied in four adult age groups. Farms differed in the quality of breeding resources they offered reproducing flies, presenting the possibility of local adaptation;No consistent departures from random mating were detected. No consistent linkage disequilibrium was observed. Allele frequencies were homogeneous among sexes and age groups. Mating patterns in subpopulations were entirely random and did not influence population breeding structure;Allele frequencies at farms were initially divergent, converged in midsummer, and then progressively diverged in each of two years. In spring, allele frequencies were heterogeneous among farms due to genetic drift during winter. This differentiation diminished rapidly in June and flies were panmictic until November. However, allele frequencies in young flies (0-3 days old) became divergent in mid-August when fly populations were large. Variation in allele frequencies in young flies at adjacent farms accounted for a large proportion of the variance in allele frequencies among all farms. These observations were consistent with the hypothesis that allele frequencies in young flies reflected the habitat in which they matured as larvae;The population biology and genetics of house flies surviving indoors during winter was studied in three swine farrowing sheds. Adult age structure was monitored and compared with the age structure normally found among flies in summer. A larger proportion of flies were gravid during winter. The other age structure indices were homogeneous with those found among summer flies. There were major shifts in allele frequencies associated with the founding of indoor populations in autumn and the founding of outdoor populations in spring. During winter, allele frequencies were temporally homogeneous.



Digital Repository @ Iowa State University,

Copyright Owner

William Cormack Black, IV



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106 pages

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Entomology Commons