Abstract
RONDA L. HAMM, TOSHIO SHONO, AND JEFFREY G. SCOTT
Department of Entomology, Comstock Hall, Cornell University, Ithaca, NY 14853
J. Econ. Entomol. 98(1): 171-176 (2005)
Abstract: Geographic variation in the chromosomal location of the male sex-determining factor (M) was studied in four house fly, Musca domestica L., populations from the eastern United States. We found a strong clinal trend (29° 41’ latitude in Florida to 44° 2’ in Maine) in which the percentage of standard XYM males increased with increasing latitude. In Florida, 100% of the males possessed the M factor on the third autosome (III M). North Carolina had 20% IIIM males and 2.35% with both YM and IIIM. Fewer IIIM males were found in New York (4.35%). Populations from Maine contained 100% XYM males. In two of three standard laboratory-susceptible strains, all males carried M on an autosome (“autosomal males” or A M): CS (IIIM) and SRS (VM). Insecticide bioassays of four field-collected strains led us to conclude that resistance is not correlated with sex determination over a broad range of insecticides. For example, high levels of resistance to permethrin (86-99% survival at a diagnostic concentration) were found in all four field-collected strains. The five other insecticides evaluated showed varying levels of resistance among field strains. We conclude that a cline is present in house fly populations from the eastern United States with 100% IIIM males in the south and entirely YM males in the north and that insecticide resistance is not a key factor influencing the evolution or linkage of M.
Factors responsible for the North-South cline in III versus Y sex determinants in the house fly
The sex determining mechanisms in the housefly vary based on latitude in the eastern United States, Japan, and Europe. There has been a selective sweep in Florida where 100% of the population has become IIIM. My overall goal is to identify which fitness characters are involved in selecting for this trait. The specific objectives follow:
1. Determine if the fitness differences between YMand IIIM are related to overwintering, temperature, development time, longevity and/or mating competition.
2. Determine if there is a cline with a higher percentage of autosomal males in the north and mostly YM males in the south (opposite of that in the northern hemisphere) in the southern hemisphere. Also to determine the linkage of the sex determining mechanisms with an autosome.
3. Develop a model of how these factors interact and could lead to the fixation of IIIM that have been observed in some populations.
Other websites of interest:
My homepage : http://www.people.cornell.edu/pages/rh99/
Scott Lab homepage http://www.entomology.cornell.edu/Faculty_Staff/Scott/
