Monday, December 10, 2007 - 8:05 AM

M versus F: Is it really a battle of the sexes?

Ronda L. Hamm,, Cornell University, Entomology, 6142 Comstock Hall, Ithaca, NY and Jeffrey G. Scott,, Cornell University, Department of Entomology, 6134 Comstock Hall, Ithaca, NY.

In the house fly, Musca domestica L., sex is determined by a dominant factor, M, located on the Y chromosome.  However, there are "autosomal male" (AM) strains in which the M factor is located on one or more of the five autosomes (I-V) or even on X.  The appearance of autosomal males is not random. Latitudinal clines exist in Europe and the United States.  It is unknown whether the frequency of AM versus YM males is stable in populations over time.  Populations that contain males with multiple M factors (IIIM and YM for example) or males homozygous for an AM factor contain an F factor to produce females. 

The linkage of sex determination under two different environmental conditions was studied in the house fly.  We compared the linkage of M in North Carolina populations after a four year period in the laboratory or the field.  In 2002 male house flies were 77.65% YM, 20% IIIM, and 2.35% with both IIIM and YM.  After 4 years in the laboratory, the frequency had changed to include homozygous males and had eliminated autosomal males.  The frequencies in the field were similar to that of 4 years ago with the addition of the XMYM genotype.  The presence of homozygous M males offered the opportunity to evaluate the frequency of the female determining F factor.  F was found to be present in both the lab and field populations, but frequencies varied. 

Species 1: Diptera Muscidae Musca domestica (house fly)